Originally, masonry was the art of building structures from stone. Today, it refers to construction consisting of units held together with mortar, constructions such as concrete block, stone, brick, clay tile products, and, sometimes, glass block. The characteristics of masonry work are determined by the properties of the masonry units

When you have completed this course, you will be able to:

Contents

1.0.0 Masonry Tools and Equipment

2.0.0 Concrete Masonry

3.0.0 Concrete Masonry Construction

4.0.0 Brick Masonry

Review Questions


1.0.0 MASONRY TOOLS and EQUIPMENT

 Masonry involves the use of a wide selection of tools and equipment. A set of basic mason’s tools, includes trowels, a chisel, hammer, and a jointer.

1.1.0 Trowels

Figure 1 – Trowels.

The trowels shown in Figure 1 are used to pick up mortar from the board, throw it on the unit, spread the mortar, and tap the unit down into the bed. A common trowel is usually triangular, ranging in size up to about 11 inches long and from 4 to 8 inches wide. Generally, short, wide trowels are best because they do not put too much strain on the wrist. Trowels used to point and strike joints are smaller, ranging from 3 to 6 inches long and 2 to 3 inches wide. We will talk more about pointing and striking joints later in the course.

1.2.0 Chisel

Figure 2 – Chisel or bolster.

The chisel, or bolster, shown in Figure 2, is used to smooth cut masonry units into parts. A typical chisel is 2 1/2 to 4 1/2 inches wide.

1.3.0 Hammer

Figure 3 – Hammer.

The mason’s hammer, shown in Figure  3, has a square face on one end and a long chisel on the other. The hammer weighs from 1 1/2 to 3 1/2 pounds. You use it to split and rough-break masonry units.

1.4.0 Jointer


Figure 4 – Jointer.

As its name implies, you use the jointer shown in Figure 4 to make various mortar joints. There are several different types of jointer; rounded, flat, or pointed; depending on the shape of the mortar joint you want.

1.5.0 Square


Figure 5 – Square.

Use the square, shown in Figure 5, to measure right angles and to lay out corners. Squares are usually made of metal and come in various sizes.

1.6.0 Mason’s Level

Figure 6 – Mason’s level.

The mason’s level shown in Figure 6 is used to establish plumb and level lines. A plumb line is absolutely vertical. A level line is absolutely horizontal. The level may be constructed of seasoned hardwood, various metals, or a combination of both. They are made as lightweight as possible without sacrificing strength to withstand fairly rough treatment. Levels may be equipped with single or double vials. Double vial levels are preferred since they can be used either horizontally or vertically.

Levels are shaped similar to rulers and have vials enclosed in glass. Inside each vial is a bubble of air suspended in either alcohol or oil. When a bubble is located exactly between the two center marks on the vial, the object is either level or plumb, depending on the position in which the mason is using the level. In a level, alcohol is the more suitable since oil is more affected by heat and cold. The term “spirit level” indicates that the vials contain alcohol. The vials are usually embedded in plaster or plastic so that they remain secure and true. Shorter levels are made for jobs where a longer level will not fit. The most popular of these are 24 and 18 inches long.

In a level constructed of wood, occasionally rub a small amount of linseed oil into the wood with a clean cloth. This treatment also stops mortar from sticking to the level. Do not use motor oil as it eventually rots the wood.

1.7.0 Straightedge

Figure 7 – Straightedge.

The straightedge, shown in Figure 7, can be any length up to 16 feet. Thickness can be from 1 1/8 inches to 1 1/2 inches, and the middle portion of the top edge from 6 to 10 inches wide. The middle portion of the top edge must be parallel to the bottom edge. Use a straightedge to extend a level to plumb or level distances longer than the level length.

1.8.0 Miscellaneous Items

Other mason’s tools and equipment include shovels, mortar hoes, wheelbarrows, chalk lines, plumb bobs, and a 200 foot ball of good quality mason’s line. Be sure to keep wheelbarrows and mortar tools clean; hardened mortar is difficult to remove. Clean all tools and equipment thoroughly at the end of each day or when the job is finished.

Figure 8 – Mortar mixing machine.

The mortar mixing machine shown in Figure 8 is used for mixing large quantities of mortar. The mixer consists primarily of a metal drum containing mixing blades mounted on a chassis equipped with wheels for towing the machine from one job site to another. The mixer is powered by either an electric motor or a gasoline engine. After mixing, the mortar is discharged into a mortar box or wheelbarrow, usually by tilting the mixer drum. As with any machine, refer to the manufacturer’s operator and maintenance manuals for proper operation. Be sure to follow safety requirements related to mixer operations.

Test Your Knowledge

1. As a builder, you should use a mason’s hammer for which of the following tasks?

A. Smooth-cutting concrete masonry units
B. Chipping and rough cutting concrete masonry units
C. Checking level courses
D. Laying out corners

 

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2.0.0 CONCRETE MASONRY

One of the most common masonry units is the concrete block. It consists of hardened cement and may be completely solid or contain single or multiple hollows. It is made from conventional cement mixes and various types of aggregate, including sand, gravel, crushed stone, air cooled slag, coal cinders, expanded shale or clay, expanded slag, volcanic cinders (pozzolan), pumice, and Scotia (refuse obtained from metal ore reduction and smelting). The term concrete block was formerly limited to only hollow masonry units made with such aggregates as sand, gravel, and crushed stone. Today, the term covers all types of concrete block, both hollow and solid, made with any kind of aggregate. Concrete blocks are also available with applied glazed surfaces, various pierced designs, and a wide variety of surface textures.

Concrete blocks are used in all types of masonry construction. The following are just a few of many examples:

Although concrete block is made in many sizes and shapes, and in both modular and nonmodular dimensions, its most common unit size is 7 5/8 by 7 5/8 by 15 5/8 inches. This size is known as 8 by 8 by 16 inch block nominal size. All concrete block must meet certain specifications covering size, type, weight, moisture content, compressive strength, and other characteristics. Properly designed and constructed concrete masonry walls satisfy many building requirements, including fire prevention, safety, durability, economy, appearance, utility, comfort, and acoustics.

2.1.0 Block Sizes and Shapes

Figure 9 – Typical unit sizes and shapes of concrete masonry units.

Concrete masonry units are available in many sizes and shapes to fit different construction needs. Both full and half length sizes are shown in Figure 9. Because concrete block sizes usually refer to nominal dimensions, a unit actually measuring 7 5/8 by 7 5/8 by 15 5/8 inches is called an 8 by 8 by 16 inch block. When laid with 3/8 inch mortar joints, the unit occupies a space exactly 8 by 8 by 16 inches. There are five main types of concrete masonry units:

  1. Hollow load-bearing concrete block
  2. Solid load-bearing concrete block
  3. Hollow non-load bearing concrete block
  4. Concrete building tile
  5. Concrete brick

Load-bearing blocks are available in two grades, N and S. Grade N is for general use, such as exterior walls both above and below grade that may or may not be exposed to moisture penetration or weather. Both grades are also used for backup and interior walls. Grade S is for above grade exterior walls with a weather protective coating and for interior walls. The grades are further subdivided into two types. Type I consists of moisture controlled units for use in arid climates. Type II consists of non moisture controlled units.

American Society for Testing and Materials (ASTM) specifications define a solid concrete block as having a core area not more than 25 percent of the gross cross sectional area. Most concrete bricks are solid and sometimes have a recessed surface like the frogged brick shown in Figure 9. In contrast, a hollow concrete block has a core area greater than 25 percent of its gross cross sectional area, generally 40 percent to 50 percent.

Blocks are considered heavyweight or lightweight, depending on the aggregate used in their production. A hollow load-bearing concrete block 8 by 8 by 16 inches nominal size weighs from 40 to 50 pounds when made with a heavyweight aggregate such as sand, gravel, crushed stone, or air cooled slag. The same size block weighs only 25 to 35 pounds when made with coal cinders, expanded shale, clay, slag, volcanic cinders, or pumice. The choice of blocks depends on both the availability of the blocks and requirements of the intended structure.

Figure 10 – Masonry saw.

Blocks may be cut with a chisel, but they can be cut more conveniently and accurately with a power driven masonry saw, shown in Figure 10. Be sure to follow the manufacturer’s manual for operation and maintenance. As with all electrically powered equipment, follow all safety guidelines.

2.2.0 Block Mortar Joints

The sides and the recessed ends of a concrete block are called the shell. The material that forms the partitions between the cores is called the web. Each of the long sides of a block is called a face shell. Each of the recessed ends is called an end shell. The vertical ends of the face shells, on either side of the end shells, are called the edges. You can see the relationship of these components in a stretcher block in Figure 11.

Figure 11 – Components of a stretcher block.

Bed joints on first courses and bed joints in column construction are mortared by spreading a 1 inch layer of mortar. This procedure is referred to as full mortar bedding. For most other bed joints, only the upper edges of the face shells need to be mortared. This is referred to as face shell mortar bedding.

Head joints may be mortared by buttering both edges of the block being laid or by buttering one edge on the block being laid and the opposite edge on the block already in place.

2.3.0 Masonry Mortar

Properly mixed and applied mortar is necessary for good workmanship and good masonry service because it must bond the masonry units into a strong, well-knit structure. The mortar that bonds concrete block, brick, or clay tile will be the weakest part of the masonry unless you mix and apply it properly. When masonry leaks, it is usually through the joints. Both the strength of masonry and its resistance to rain penetration depend largely on the strength of the bond between the masonry unit and the mortar. Various factors affect bond strength, including the type and quantity of the mortar, its plasticity and workability, its water retentivity, the surface texture of the mortar bed, and the quality of workmanship in laying the units. You can correct irregular brick dimensions and shape with a good mortar joint.

2.3.1 Workability of Mortar

Mortar must be plastic enough to work with a trowel. You obtain good plasticity and workability by using mortar having good water retentivity, using the proper grade of sand, and thorough mixing. You do not obtain good plasticity by using a lot of cementitious materials. Mortar properties depend largely upon the type of sand the mortar contains. Clean, sharp sand produces excellent mortar, but too much sand causes mortar to segregate, drop off the trowel, and weather poorly.

2.3.2 Water Retentivity

Water retentivity is the mortar property of resistance to rapid loss of water to highly absorbent masonry units. Mortar must have water to develop the bond. If it does not contain enough water, the mortar will have poor plasticity and workability, and the bond will be weak and spotty. Sometimes, you must wet brick to control water absorption before applying mortar, but never wet concrete masonry units.

2.3.3 Mortar Strength and Durability

The type of service that the masonry must give determines the strength and durability requirements of mortar. For example, walls subject to severe stress or weathering must be laid with more durable, stronger mortar than walls for ordinary service. Table 1 gives mortar mix proportions that provide adequate mortar strength and durability for the conditions listed.

Table 1 – Recommended Mortar Mix Proportions by Unit Volume.

2.3.4 Types of Mortar

The following mortar types are proportioned on a volume basis:

2.4.0 Mixing Mortar

The manner in which mortar is mixed has a lot to do with the quality of the final product. In addition to machine and hand mixing, you need to know the requirements for introducing various additives, including water, to the mix in order to achieve optimum results.

2.4.1 Machine Mixing

Machine mixing refers to mixing large quantities of mortar in a drum type mixer. Place all dry ingredients in the mixer first and mix them for 1 minute before adding the water. When adding water, you should always add it slowly. Minimum mixing time is 3 minutes. The mortar should be mixed until a completely uniform mixture is obtained.

2.4.2 Hand Mixing

Hand mixing involves mixing small amounts of mortar by hand in a mortar box or wheelbarrow. Take care to mix all ingredients thoroughly to obtain a uniform mixture. As in machine mixing, mix all dry materials together first before adding water. Keep a steel drum of water close at hand to use as the water supply. Also, keep all your masonry tools free of hardened mortar mix and dirt by immersing them in water when they are not in use.

2.4.3 Requirements

You occasionally need to mix lime putty with mortar. When you machine mix, use a pail to measure the lime putty. Place the putty on top of the sand. When hand mixing, add the sand to the lime putty. Wet pails before filling them with mortar and clean them immediately after emptying.

Mixing water for mortar must meet the same quality requirements as mixing water for concrete. Do not use water containing large amounts of dissolved salts, as salts weaken the mortars.

You can restore the workability of any mortar that stiffens on the mortar board due to evaporation by remixing it thoroughly. Add water as necessary, but discard any mortar stiffened by initial setting. Because it is difficult to determine the cause of stiffening, a practical guide is to use mortar within 2 1/2 hours of the original mixing. Discard any mortar you do not use within this time.

Do not use an antifreeze admixture to lower the freezing point of mortars during winter construction. The quantity necessary to lower the freezing point any appreciable degree is so large it will seriously impair the strength and other desirable properties of the mortar.

To avoid reinforcing steel (RST) corrosion, do not add calcium chloride unless specified by specifications.

2.5.0 Modular Planning

Concrete masonry walls should be laid out to make maximum use of full and half length units. This minimizes cutting and fitting of units on the job. Plan the length and height of walls, width and height of openings, and wall areas between doors, windows, and corners to use full size and half size units, which are usually available (Figure 12). This procedure assumes that window and door frames are of modular dimensions which fit modular full and half size units. Then, all horizontal dimensions should be in multiples of nominal full length masonry units.

Figure 12 – Planning concrete masonry wall openings.

Design both horizontal and vertical dimensions in multiples of 8 inches. Table 2 lists nominal length of concrete masonry walls by stretchers.

Table 2 – Nominal Lengths of Concrete Masonry Walls in Stretchers.

Table 3 lists nominal height of concrete masonry walls by courses. When using 8 by 4 by 16 units, plan the horizontal dimensions in multiples of 8 inches (half length units) and the vertical dimensions in multiples of 4 inches. If the thickness of the wall is greater or less than the length of a half unit, a special length unit is required at each corner in each course.

Table 3 – Nominal Heights of Modular Concrete Masonry Walls in Courses.

Table 4 lists the average number of concrete masonry units by size and approximate number of cubic feet of mortar required per 100 square feet of concrete masonry wall.

Table 4 – Average Concrete Masonry Units and Mortar per 100 square feet of Wall.

Table 5 lists the number of 16 inch blocks per course for any wall.

Table 5 – Number of 16 Inch Blocks per Course.

Always use outside measurements when calculating the number of blocks required per course. For example, a basement 22 feet by 32 feet should require 79 blocks for one complete course. Multiply 79 by the number of courses needed. Thus, a ten course basement requires a total of 790 blocks for a solid wall, from which deductions should be made for windows and doors. If any dimension is an odd number, use the nearest smaller size listed in the table. For example, for a 22 foot by 31 foot enclosure, use 22 feet by 30 feet and add one half block per row.

As a builder, you might find yourself in the field without the tables handy, so here is another method. Use 3/4 times the length and 3/2 times the height for figuring how many 8 by 8 by 16 inch blocks you need for a wall. Let’s take an example:

Example

Given: A wall 20 feet long x 8 feet high

3/4 x 20 = 60 ÷ 4 = 15 (8” x 8” x16” block per course)

3/2 x 8 = 24 ÷ 2 = 12 courses high

15 x 12 = 180 total blocks

2.6.0 Estimating Mortar

You can use rule 38 for calculating the raw material needed to mix 1 yard of mortar without a great deal of paperwork. This rule does not accurately calculate the required raw materials for large masonry construction jobs. For larger jobs, use the absolute volume or weight formula. In most cases, and particularly in advanced base construction, you can use rule 38 to quickly estimate the quantities of the required raw materials. Builders have found that it takes about 38 cubic feet of raw materials to make 1 cubic yard of mortar.  (Rule 38)

In using rule 38 for calculating mortar, take the rule number and divide it by the sum of the quantity figures specified in the mix. For example, let’s assume that the building specifications call for a 1:3 mix for mortar:

  1. Add 1:3, which gives you 4.
  2. Divide 38 by 4 to figure the prime number. 38 ÷ 4 = 9 1/2 cubic feet
  3. Compute your material requirements by multiplying the prime number by the ratio as follows:
            1 x 9 1/2 = 9 1/2 cubic feet of cement    
            3 x 9 1/2 = 28 1/2 cubic feet of sand

Using these calculations, you find that you’ll need 9 1/2 cubic feet (sacks) of cement and 28 1/2 cubic feet of sand to mix 1 cubic yard of mortar using a 1:3 mix. The sum of the two required quantities should always equal 38. This is how you can check whether you are using the correct amounts. In the above example, 9 1/2 sacks of cement plus 28 1/2 cubic feet of sand equal 38. Be careful with your calculations, as too much sand in your mortar can cause segregation.

2.7.0 Safe Handling of Material

When you handle cement or lime bags, wear goggles and snug fitting neckbands and wristbands. Always practice good personal cleanliness and never wear clothing that has become stiff with cement. Cement impregnated clothing irritates the skin and may cause serious infection. Report any susceptibility of the skin to cement and lime burns. Personnel who are allergic to cement or lime should be transferred to other jobs.

Do not pile bags of cement or lime more than 10 bags high on a pallet. The only exception is when storage is in bins or enclosures built for such storage. Place the bags around the outside of the pallet with the mouths of the bags facing the center. Be sure to cross pile the first five tiers of bags each way from any corner. Make a setback starting with the sixth tier to prevent piled bags from falling outward. If you have to pile bags above 10 tiers, make another setback. The back tier, when not resting against an interior wall of sufficient strength to withstand the pressure, should be set back on bag every five tiers, the same as the end tiers. During unpiling, keep the entire top of the pile level and maintain the necessary setbacks.

Lime and cement must be stored in a dry place. This helps prevent the lime from crumbling and the cement from hydrating before it is used.

Test Your Knowledge

2. Excess sand in a mortar mix causes which of the following problems?

A. Slow setting
B. Segregation
C. Stickiness
D. Lumps

3. A single course in a 10 foot long block wall requires how many standard blocks?

A. 5 1/2
B. 6 1/2
C. 7 1/2
D. 8 1/2

4. Building specifications call for a 1:2 mortar mix. Using rule 38, how many sacks of cement are required to make up a 2 cubic yard mix?

A. 7
B. 13
C. 20
D. 26

 

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3.0.0 CONCRETE MASONRY CONSTRUCTION

Good workmanship is a very important factor in building masonry walls. Make every effort to lay each masonry unit plumb and true. In the following paragraphs, we will discuss the basic steps in laying up masonry walls.

3.1.0 Steps in Construction

Start building a concrete masonry wall by locating the corners of the structure. In locating the corners, also make sure the footing or slab formation is level so that each Builder starts each section wall on a common plane. This also helps ensure that the bed joints are straight when the sections are connected. If the foundation is badly out of level, the entire first course should be laid before Builders begin working on other courses. If this is not possible, a level plane should be established with a transit or engineer’s level.

Next chase out bond, or lay out, by placing the first course of blocks without mortar, as shown in Figure 13. Snap a chalk line to mark the footing and align the blocks accurately. Then, use a piece of material 3/8 inch thick to properly space the blocks. This helps you get an accurate measurement.

Figure 13 – Placing blocks without mortar (chasing the bond).

Replace the loose blocks with a full mortar bed, spreading and furrowing it with a trowel to ensure plenty of mortar under the bottom edges of the first course, as shown in Figure 14.

Figure 14 – Spreading and furrowing mortar bed.

Figure 15 – Positioning and aligning corner block.

Carefully position and align the corner block first, as shown in Figure 15. Lay the remaining first course blocks with the thicker end up to provide a larger mortar bedding area.

For the vertical joints, apply mortar only to the block ends by placing several blocks on end and buttering them all in one operation, as shown in Figure 16. Make the joints 3/8 inch thick. Then, place each block in its final position, and push the block down vertically into the mortar bed and against the previously laid block. This ensures a well filled vertical mortar joint.

Figure 16 – Laying first course of blocks for a wall.

After laying three or four blocks, use a mason’s level as a straightedge to check correct block alignment, as shown in Figure 17.

Figure 17 – Leveling block for a wall.

Use the level to bring the blocks to proper grade and plumb them by tapping with a trowel handle, as shown in Figure 18. Always lay out the first course of concrete masonry carefully and make sure that you properly align, level, and plumb it.

This assures that succeeding courses and the final wall are both straight and true.

Figure 18 - Plumbing block for a wall.

Build up the corners of the wall, usually four or five courses high. This is also called laying up a lead. Step back each course one half block. For the horizontal joints, apply mortar only to the tops of the blocks already laid. For the vertical joints, you can apply mortar either to the ends of the new block or the end of the block previously laid, or both, to ensure well filled joints, as shown in Figure 19.

Figure 19 – Completed corner leads.

Figure 20 – Checking for alignment.

As you lay each course at the corner, check the course with a level for alignment, as shown in Figure 20, for level (Figure 21) view B and for plumb (Figure 22). Carefully check each block with a level or straightedge to make sure that all the block faces are in the same plane. This ensures true, straight walls.

 Figure 21 – Checking for level.

 Figure 22 – Checking for plumb.

The folding rule, shown in Figure 23, helps accurately place each masonry course.

Figure 23 – Using a folding rule to check course height.

Also check the horizontal block spacing by placing a level diagonally across the corners of the blocks, shown in Figure  24.

Figure 24 – Checking horizontal block spacing.

When filling in the wall between the corners, first stretch a mason’s line along the extensor block edges from corner to corner for each course. Then lay the top outside edge of each new block to this line, as shown in Figure 25. How you grip a block before laying is important. First, tip it slightly toward you so that you can see the edge of the course below. Then place the lower edge of the new block directly on the edges of the block below, shown in Figure 25.

Figure 25 – Filling in the wall between corners.

Make all position adjustments while the mortar is soft and plastic. Any adjustments after the mortar stiffens will break the mortar bond and allow water to penetrate. Level each block and align it to the mason’s line by tapping it lightly with a trowel handle.

Before installing the closure block, butter both edges of the opening and all four vertical edges of the closure block with mortar. Then lower the closure block carefully into place as shown in Figure 26. If any mortar falls out, leaving an open joint, remove the block and repeat the procedure.

Figure 26 – Installing a closure block.

Figure 27 – Cutting off excess mortar from the joints.

To assure a good bond, do not spread mortar too far ahead when actually laying blocks. If you do, the mortar will stiffen and lose its plasticity. The recommended width of mortar joints for concrete masonry units is 3/8 inch. When properly made, these joints produce a weathertight, neat, and durable concrete masonry wall. As you lay each block, cut off excess mortar from the joints using a trowel, as shown in Figure 27, and throw it back on the mortar board to rework into the fresh mortar. Do not rework any mortar dropped on the scaffold or floor.

Weathertight joints and the neat appearance of concrete masonry walls depend on proper striking, or tooling. After laying a section of the wall, tool the mortar joint when the mortar becomes thumb print hard. Tooling compacts the mortar and forces it tightly against the masonry on each side of the joint. Use either concave or V-shaped tooling on all joints, as shown in Figure 28.

Tool horizontal joints as shown in Figure 29 A with a long jointer first, followed by tooling the vertical joints as shown in Figure 30. Trim off mortar burrs from the tooling flush with the wall face using a trowel or a soft bristle brush or by rubbing with a burlap bag.

Figure 28 – Tooled mortar joints for weathertight exterior walls.

Figure 29 – Striking horizontal joints.

Figure 30 – Striking vertical joints.

A procedure known as pointing may be required after jointing. Pointing is the process of inserting mortar into horizontal and vertical joints after the unit has been laid. Pointing is done to restore or replace deteriorated surface mortar in old work; this is called tuck pointing. Pointing may be necessary in freshly laid masonry to fill holes or correct defective joints.

You must prepare in advance for installing wood plates with anchor bolts on top of hollow concrete masonry walls. Place pieces of metal lath in the second horizontal mortar joint from the top of the wall under the cores that will contain the bolts, as shown in Figure 31. Use anchor bolts 1/2 inch in diameter and 18 inches long; space them not more than 4 feet apart. When you complete the top course, insert the bolts into the cores of the top two courses and fill the cores with concrete or mortar. The metal lath underneath holds the concrete or mortar filling in place. The threaded end of the bolt should extend above the top of the wall as shown in Figure 32.


Figure 31 – Placing metal lath under cores.

Figure 32 – Threaded bolt extends above wall top.

3.2.0 Control Joints

Control joints, shown in Figure 33, are continuous vertical joints that permit a masonry wall to move slightly under unusual stress without cracking. There are a number of types of control joints built into a concrete masonry wall.


Figure 33 – Control joint made up with full and half length blocks.

The most preferred control joint is the Michigan type made with roofing felt. A strip of felt is curled into the end core, covering the end of the block on one side of the joint (Figure 34). As the other side of the joint is laid, the core is filled with mortar. The filling bonds to one block, but the paper prevents bond to the block on

Figure 34 – Control joint made with the other side of the control joint. roofing felt.

Figure 35 shows the tongue and groove type of control joint. The special units are manufactured in sets consisting of full and half blocks. The tongue of one unit fits into the groove of another unit or into the open end of a regular flanged stretcher. The units are laid in mortar exactly the same as any other masonry units, including mortar in the head joint. Part of the mortar is allowed to remain in the vertical joint to form a backing against which the caulking can be packed.

Figure 35 – Control joint blocks
(top view).

Figure 36 – Z bar joint
(top view).

Figure 36 shows a control joint that may be built with regular full and half length stretcher blocks with a Z shaped bar across the joint or a 10 or 12 inch pencil rod (1/4 inch smooth bar) across each face shell. If you use a pencil rod, it must be greased on one side of the joint to prevent bond. Place these rods every other course. Lay up control joints in mortar just as any other joint. If they are exposed to either the weather or to view, caulk them as well.

After the mortar is stiff, rake it out to a depth of about 3/4 inch to make a recess for the caulking compound. Use a thin, flat caulking trowel to force the compound into the joint as shown in Figure 37.

The location of control joints is established by the architectural engineer and should be noted in the plans and specifications.

3.3.0 Walls

Walls are differentiated into two types, load-bearing and non-load-bearing. Load-bearing walls separate spaces, and also provide structural support for whatever is above them. Non-load-bearing walls are solely partitions between spaces.

Figure 37 – Raking joint to prepare for caulking.

3.3.1 Load-bearing Walls

Do not join intersecting concrete block load-bearing walls with a masonry bond, except at the corners. Instead, terminate one wall at the face of the second wall with a control joint. Then, tie the intersecting walls together with Z shaped metal tie bars 1/4 by 1/4 by 28 inches in size, with 2 inch right angle bends on each end. Space the tie bars no more than 4 feet apart vertically and place pieces of metal lath under the block cores that will contain the tie bars ends (Figure 38). Embed the right-angle bends in the cores by filling them with mortar or concrete as shown in Figure 39.

Figure 38 – Z-shaped tie bar has right angle bends at each end.

Figure 39 – Filling core with mortar or concrete.

3.3.2 Nonload-bearing Walls

To join intersecting nonload-bearing block walls, terminate one wall at the face of the second with a control joint. Place strips of metal lath of 1/4 inch mesh galvanized hardware cloth across the joint between the two walls, as shown in Figure 40, in alternate courses. Insert one half of the metal stops into one wall as you build it, and then tie the other halves into the mortar joints as you lay the second wall, as shown in Figure 41.

Figure 40 – Metal lath spans the joint between the walls.

Figure 41 – Set lath in mortar joint as you construct the second wall.

3.4.0 Bond Beams,

Lintels, and Sills Bond beams are reinforced courses of block that bond and integrate a concrete masonry wall into a stronger unit. They increase the bending strength of the wall and are particularly needed to resist earthquake forces and the high winds of hurricanes.

They also exert restraint against wall movement, reducing the formation of cracks.

Bond beams are constructed with special shape masonry units (beam and lintel block) filled with concrete or grout and reinforced with embedded steel bars. These beams are usually located at the top of walls to stiffen them. Since bond beams have appreciable structural strength, they can be located to serve as lintels over doors and windows.

Figure 42 – Lintel made from blocks.

Figure 42 shows the use of lintel blocks to place a lintel over a metal door, using the door case for support. Lintels should have a minimum bearing of 6 inches at each end. A rule of thumb is to provide 1  inch of bearing for every foot of clear space. When bond beams are located just above the floor, they act to distribute the wall weight, making the wall a deep beam, thus helping avoid wall cracks if the floor sags. Bond beams may also be located below a window sill.

Figure 43 – Precast concrete lintel.

Modular door and window openings usually require lintels to support the blocks over the openings. You can use precast concrete lintels, as shown in Figure 43, that contain an offset on the underside like the one in Figure 44 to fit the modular openings. You can also use steel lintel angles installed with an offset on the underside, as shown in Figure 45, to fit modular openings. In either case, place a noncorroding metal plate under the lintel ends at the control joints to allow the lintel to slip and the control joints to function properly. Apply a full bed of mortar over the metal plate to uniformly distribute the lintel load.

Figure 44 – Precast concrete offset on lintel underside.

Figure 45 – Steel angles offset on lintel underside.

You usually install precast concrete sills as shown in Figure 46, following wall construction. Fill the joints tightly at the ends of the sills with mortar or a caulking compound.

Figure 46 – Installed precast concrete sills.

3.5.0 Piers and Pilasters

Piers are isolated columns of masonry; pilasters are columns or thickened wall sections built contiguous to and forming part of a masonry wall. Both piers and pilasters are used to support heavy, concentrated vertical roof or floor loads. They also provide lateral support to the walls. Piers and pilasters offer an economic advantage by permitting construction of higher and thinner walls. They may be constructed of special concrete masonry units, as shown in Figure 47, or standard units.

Figure 47 – Pilaster masonry units.

3.6.0 Reinforced Block

Walls Block walls may be reinforced vertically or horizontally. To reinforce vertically, place reinforcing rods called rebar into the cores at the specified spacing and fill the cores with a relatively high slump concrete. Place rebar at each corner and at both sides of each opening. Space vertical rebar a maximum of 32 inches on center in walls. Where splices are required, lap the bars 40 times the bar diameter. Place the concrete should in one continuous pour from foundation to plate line. A cleanout block may be placed in the first course at every rebar stud for cleaning out excess mortar and to ensure proper alignment and laps of rebars. Practical experience indicates that horizontal joint reinforcing can control cracking and achieve wall flexibility. The amount of joint reinforcement depends largely upon the type of construction.

Horizontal joint reinforcing, where required, should consist of not less than two deformed longitudinal No. 9 or heavier cold drawn steel wires. Truss type cross wires should be 1/8 inch diameter or heavier of the same quality. Figure 48 shows joint reinforcement on 16 inch vertical spacing. The location and details of bond beams, control joints, and joint reinforcing should all be shown on the drawings.

Figure 48 – Masonry wall horizontal joint reinforcement.

3.7.0 Patching and Cleaning Block Walls

Always fill holes made by nails or line pins with fresh mortar and patch mortar joints. When laying concrete masonry walls, be careful not to smear mortar on the block surfaces. Once they harden, these smears cannot be removed, even with an acid wash, nor will paint cover them. Allow droppings to dry and harden.You can then chip off most of the mortar with a small piece of broken concrete block, as shown in Figure 49, or with a trowel, as shown in Figure 50. A final brushing of the spot removes practically all the mortar, as shown in Figure 51.

Figure 49 – Chipping off mortar with a piece of broken block

Figure 50 – Chipping off mortar with a trowel.

Figure 51 – Final brushing of remaining spot.

3.8.0 Retaining Walls

The purpose of a retaining wall is to hold back a mass of soil or other material. As a result, concrete masonry retaining walls must have the structural strength to resist imposed vertical and lateral loads. The footing of a retaining wall should be large enough to support the wall and the load of the material the wall is to retain. The reinforcing must be properly located as specified in the plans. Make provisions to prevent the accumulation of water behind retaining walls. This includes the installation of drain tiles, weep holes, or both.

3.9.0 Painting Concrete Masonry

Several finishes are possible on concrete masonry construction. The finish to use in any specific situation is governed by the type of structure in which the walls will be used and the climatic conditions to which they will be exposed.

Paints now commonly used on concrete masonry walls include Portland cement paint, latex paint, oil based paint, and rubber based paint. For proper application and preparation of the different types of paint, refer to the plans, specifications, or manufacturer’s instructions.

Test Your Knowledge

5. You are constructing a concrete block wall. After the corners are located, what is the next step?

A. Spread and furrow the mortar bed for the first course.
B. Attach the guide strings to the corner stakes.
C. String out the blocks for the first course without mortar.
D. Position the corner block.

6. You are building the corners of a concrete block wall. How should you ensure the horizontal blocks are correctly spaced?

A. Place a level diagonally across the corners of the block.
B. Place a level horizontally across the corners of the block.
C. Place a level vertically across the corners of the block.
D. Place a mason’s line between the corners of the wall.

7. When reinforcing a block wall, where should you place rebars?

A. At each corner
B. At each side of a wall opening
C. At points spaced no more than 32 inches on center in the wall
D. All of the above

 

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4.0.0 BRICK MASONRY

Brick masonry is construction in which uniform units called bricks, small enough to be placed with one hand, are laid in courses with mortar joints to form walls. Bricks are kiln baked from various clay and shale mixtures. The chemical and physical characteristics of the ingredients vary considerably. These characteristics and the kiln temperatures combine to produce brick in a variety of colors and hardnesses. In some regions, individual pits yield clay or shale which, when ground and moistened, can be formed and baked into durable brick. In other regions, clay or shale from several pits must be mixed.

4.1.0 Brick Terminology

Standard U.S. bricks are 2 1/4 by 3 3/4 by 8 inches nominal size. They may have three core holes or ten core holes. Modular U.S. bricks are 2 1/4 by 3 5/8 by 7 5/8 inches nominal size. They usually have three core holes. English bricks are 3 by 4 1/2 by 9 inches, Roman bricks are 1 1/2 by 4 by 12 inches, and Norman bricks are 2 3/4 by 4 by 12 inches nominal size. Actual brick dimensions are smaller, usually by an amount equal to a mortar joint width. Bricks weigh from 100 to 150 pounds per cubic foot, depending on their ingredients and duration of firing. Fired brick is heavier than under burned brick. The six surfaces of a brick are called cull, beds, side, end, and face, as shown in Figure 52.

Figure 52 – Names of brick surfaces.

Occasionally you will have to cut brick into various shapes to fill in spaces at corners and other locations where a full brick does not fit. Figure 53 shows the more common cut shapes: half or bat, three quarter closure, quarter closure, king closure, queen closure, and split.

Figure 53 – Common cut brick shapes.

4.2.0 Types of Bricks

Brick masonry units may be solid, hollow, or architectural terra cotta. All types can serve a structural function, a decorative function, or a combination of both. The various types differ in their formation and composition.

Building brick, also called common, hard, or kiln-run brick, is made from ordinary clay or shale and fired in kilns. These bricks have no special shoring, markings, surface texture, or color. Because building bricks are generally used as the backing courses in either solid or cavity brick walls, the harder and more durable types are preferred.

Face brick is better quality and has better durability and appearance than building brick. Because of this, face bricks are used in exposed wall faces. The most common face brick colors are various shades of brown, red, gray, yellow, and white.

Clinker brick is over burned in the kiln. Clinker bricks are usually rough, hard, durable, and sometimes irregular in shape.

Pressed brick is made by a dry press process rather than by kiln firing. Pressed bricks have regular smooth faces, sharp edges, and perfectly square corners. Ordinarily, they are used like face brick.

Glazed brick has one surface coated with a white or colored ceramic glazing. The glazing forms when mineral ingredients fuse together in a glass-like coating during burning. Glazed bricks are particularly suited to walls or partitions in hospitals, dairies, laboratories, and other structures requiring sanitary conditions and ease of cleaning.

Fire brick is made from a special type of clay. This clay is very pure and uniform and is able to withstand the high temperatures of fireplaces, boilers, and similar constructions. Fire bricks are generally larger than other structural bricks and are often hand-molded.

Cored bricks have ten holes, two rows of five holes each, extending through their beds to reduce weight. Walls built from cored brick are not much different in strength than walls built from solid brick. Also, both have about the same resistance to moisture penetration. Whether cored or solid, use the more available brick that meets building requirements.

European brick has strength and durability about equal to U.S. clay brick. This is particularly true of the English and Dutch types.

Sand-lime brick is made from a lean mixture of slaked lime and fine sand. Sand-lime bricks are molded under mechanical pressure and hardened under steam pressure. They are used extensively in Germany.

4.3.0 Strength of Brick Masonry

The main factors governing the strength of a brick structure include brick strength, mortar strength and elasticity, bricklayer workmanship, brick uniformity, and the method used to lay the brick. In this section, we’ll cover strength and elasticity. Workmanship is covered separately in the next section.

The strength of a single brick masonry unit varies widely, depending on its ingredients and manufacturing method. Brick can have an ultimate compressive strength as low as 1,600 psi. On the other hand, some well burned brick has compressive strength exceeding 15,000 psi.

Because Portland cement lime mortar is normally stronger than the brick, brick masonry laid with this mortar is stronger than an individual brick unit. The load carrying capacity of a wall or column made with plain lime mortar is less than half that made with Portland cement lime mortar. The compressive working strength of a brick wall or column laid with plain lime mortar normally ranges from 500 to 600 psi.

For mortar to bond to brick properly, sufficient water must be present to completely hydrate the Portland cement in the mortar. Bricks sometimes have high absorption rates, and, if not properly treated, can suck the water out of the mortar, preventing complete hydration. Here is a quick field test to determine brick absorptive qualities. Using a medicine dropper, place 20 drops of water in a 1 inch circle, about the size of a quarter, on a brick. A brick that absorbs all the water in less than 1 1/2 minutes will suck the water out of the mortar when laid. To correct this condition, thoroughly wet the bricks and allow the surfaces to air dry before placing.

4.4.0 Bricklaying Methods

Good bricklaying procedure depends on good workmanship and efficiency. Efficiency involves doing the work with the fewest possible motions. Each motion should have a purpose and accomplish a definite result. After learning the fundamentals, every Builder should develop methods for achieving maximum efficiency. The work must be arranged in such a way that the Builder is continually supplied with brick and mortar. The scaffolding required must be planned before the work begins. It must be built in such a way as to cause the least interference with other crewmembers.

Bricks should always be stacked on planks; they should never be piled directly on uneven or soft ground. Do not store bricks on scaffolds or runways. This does not prohibit placing normal supplies on scaffolding during actual bricklaying operations. Except where stacked in sheds, brick piles should never be more than 7 feet high. When a pile of brick reaches a height of 4 feet, it must be tapered back 1 inch in every foot of height above the 4 foot level. The tops of brick piles must be kept level, and the taper must be maintained during unpiling operations.

4.5.0 Masonry Terms

To efficiently and effectively lay bricks, you must be familiar with the terms that identify the position of masonry units and mortar joints in a wall. The following list, which references Figure 54 through Figure 60, provides some of the basic terms you will encounter.

A course, shown in Figure 54, is one of several continuous, horizontal layers (or rows) of masonry units bonded together.

Figure 54 – Course.

Figure 55 – Wythe.

A wythe, shown in Figure 55, is each continuous, vertical section of a wall; each section is one masonry unit thick. It is sometimes called a tier.

A stretcher, shown in Figure 56, is a masonry unit laid flat on its bed along the length of a wall with its face parallel to the face of the wall.

Figure 56 – Stretcher.

Figure 57 – Header.

A header, shown in Figure 57, is a masonry unit laid flat on its bed across the width of a wall with its face perpendicular to the face of the wall. It is generally used to bond two wythes.

A rowlock, shown in Figure 58, is a header laid on its face or edge across the width of a wall.

Figure 58 – Rowlock.

Figure 59 – Bull header and bull stretcher.

A bull header, shown in Figure 59, is a rowlock brick laid with its bed perpendicular to the face of the wall. A bull stretcher, also shown in Figure 59, is a rowlock brick laid with its bed parallel to the face of the wall.

Figure 60 – Soldier.

 A soldier, shown in Figure 60, is a brick laid on its end with its face perpendicular to the face of the wall.

4.6.0 Bonds

The term “bond”, as used in masonry, has three different meanings: structural bond, mortar bond, or pattern bond. Structural bond refers to how the individual masonry units interlock or tie together into a single structural unit.

You can achieve structural bonding of brick and tile walls in one of three ways:

Mortar bond refers to the adhesion of the joint mortar to the masonry units or to the reinforcing steel.

Pattern bond refers to the pattern formed by the masonry units and mortar joints on the face of a wall. The pattern may result from the structural bond, or may be purely decorative and unrelated to the structural bond. Figure 44 shows the six basic pattern bonds in common use today: running, common or American, Flemish, English, stack, and English cross or Dutch bond.

The running bond, shown in Figure 61, is the simplest of the six patterns, consisting of all stretchers. Because the bond has no headers, metal ties usually form the structural bond. The running bond is used largely in cavity wall construction, brick veneer walls, and facing tile walls made with extra wide stretcher tile.

Figure 61 – Running bond.

Figure 62 – English bond.

The English bond, shown in Figure 62, consists of alternating courses of headers and stretchers. The headers center over and under the stretchers. The joints between stretchers in all stretcher courses do not align vertically. You can use blind headers in courses that are not structural bonding courses.

The common or American bond, shown in Figure 63, is a variation of the running bond, having a course of full length headers at regular intervals that provide the structural bond as well as the pattern. Header courses usually appear at every fifth, sixth, or seventh course, depending on the structural bonding requirements. You can vary the common bond with a Flemish header course. In laying out any bond pattern, be sure to start the corners correctly. In a common bond, use a three-quarter closure at the corner of each header course.

Figure 63 – Common or American bond.

Figure 64 – Flemish bond.

In the Flemish bond, shown in Figure 64, each course consists of alternating headers and stretchers. The headers in every other course center over and under the stretchers in the courses in between. The joints between stretchers in all stretcher courses align vertically. When headers are not required for structural bonding, you can use bricks called blind headers. You can start the corners in two different ways. In the Dutch corner, a three quarter closure starts each course. In the English corner, a 2 inch or quarter closure starts the course.

The stack bond, shown in Figure 65, is purely a pattern bond, with no overlapping units and all vertical joints aligning. You must use dimensionally accurate or carefully rematched units to achieve good vertical joint alignment. You can vary the pattern with combinations and modifications of the basic patterns shown in Figures 8-61 through 8-66. This pattern usually bonds to the backing with rigid steel ties or 8 inch thick stretcher units when available. In large wall areas or load-bearing construction, insert steel pencil rods into the horizontal mortar joints as reinforcement.

Figure 65 – Stack bond.

Figure 66 – English cross or Dutch bond.

The English cross or Dutch bond, shown in Figure 66, is a variation of the English bond. It differs only in that the joints between the stretchers in the stretcher courses align vertically. These joints center on the headers in the courses above and below.


Figure 67 – Metal ties.

When a wall bond has no header courses, use metal ties to bond the exterior wall brick to the backing courses. Figure 67 shows three typical metal ties.

Install flashing at any spot where moisture is likely to enter a brick masonry structure. Flashing diverts the moisture back outside. Always install flashing under horizontal masonry surfaces, such as sills and copings; at intersections between masonry walls and horizontal surfaces, such as a roof and parapet or a roof and chimney; above openings, doors and windows, for example; and frequently at floor lines, depending on the type of construction. The flashing should extend through the exterior wall face and then turn downward against the wall face to form a drop.

Provide weep holes at intervals of 18 to 24 inches to drain water to the outside that might accumulate on the flashing. Weep holes are even more important when appearance requires the flashing to stop behind the wall face instead of extending through the wall. This type of concealed flashing, when combined with tooled mortar joints, often retains water in the wall for long periods and, by concentrating the moisture at one spot, does more harm than good.

4.7.0 Mortar Joints and Pointing

There is no set rule governing the thickness of a brick masonry mortar joint. Irregularly shaped bricks may require mortar joints up to 1/2 inch thick to compensate for the irregularities. Mortar joints 1/4 inch thick are the strongest. Use this thickness when the bricks are regular enough in shape to permit it.

A slushed joint is made simply by depositing the mortar on top of the head joints and allowing it to run down between the bricks to form a joint. You cannot make solid joints this way. Even if you fill the space between the bricks completely, there is no way you can compact the mortar against the brick faces; consequently a poor bond results. The only effective way to build a good joint is to trowel it.

The secret of mortar joint construction and pointing is in how you hold the trowel for spreading mortar. Figure 68 shows the correct way to hold a trowel. Hold it firmly in the grip shown, with your thumb resting on top of the handle, not encircling it.

Figure 68 – Correct way to hold a trowel.

If you are right handed, pick up mortar from the outside of the mortar board pile with the left edge of your trowel as shown in Figure 69. A pickup for one brick forms only a small pile along the left edge of the trowel. You can pick up enough to spread one to five bricks, depending on the wall space and your skill. A pickup for five bricks is a full load for a large trowel, as shown in Figure 70.

Figure 69 – Proper way to pick up mortar right-handed.

Figure 70 – Fully loaded trowel for five bricks.

If you are right handed, work from left to right along the wall. Holding the left edge of the trowel directly over the center line of the previous course, tilt the trowel slightly and move it to the right as shown in Figure 71.

Figure 71 – Working from left to right.

Figure 72 – Spreading mortar on three to five bricks at a time.

Spread an equal amount of mortar on each brick until you either complete the course or the trowel is empty, as shown in Figure 72. Return any mortar left over to the mortar board.

Figure 73 – A poorly bonded brick.

Do not spread the mortar for a bed joint too far ahead of laying; four or five brick lengths is best. Mortar spread out too far ahead dries out before the bricks become bedded and causes a poor bond, as shown in Figure 73. The mortar must be soft and plastic so that the brick will bed in it easily.

Spread the mortar about 1 inch thick and then make a shallow furrow in it as shown in Figure 74. A furrow that is too deep leaves a gap between the mortar and the bedded brick. This reduces the resistance of the wall to water penetration.

Figure 74 – Making a furrow.

Figure 75 – Cutting off excess mortar.

Use a smooth, even stroke to cut off any mortar projecting beyond the wall line with the edge of the trowel as shown in Figure 75. Retain enough mortar on the trowel to butter the left end of the first brick you will lay in the fresh mortar. Throw the rest back on the mortar board.

Pick up the first brick to be laid with your thumb on one side of the brick and your fingers on the other, as shown in Figure 76. Apply as much mortar as will stick to the end of the brick and then push it into place.

Figure 76 – Proper way to hold a brick when buttering the end.

Figure 77 – Making a head joint in a stretcher course.

Squeeze out the excess mortar at the head joint and at the sides as shown in Figure 77. Make sure the mortar completely fills the head joint. After bedding the brick, cut off the excess mortar and use it to start the next end joint. Throw any surplus mortar back on the mortar board where it can be restored to workability.

To insert a brick into a space left in a wall.

  1. Spread a thick bed of mortar as shown in Figure 78.
  2. Shove the brick into the wall space as shown in Figure 79.
  3. Mortar squeezes out of all four joints as shown in Figure 80. This way, you know that the joints are full of mortar at every point.

Figure 78 – Spreading a thick bed of mortar.

Figure 79 – Shoving the brick into place.

Figure 80 – Mortar squeezes out all four joints.

To make a cross joint in a header course:

  1. Spread the bed joint mortar several brick widths in advance.
  2. Spread mortar over the face of the header brick before placing it in the wall as shown in Figure 81.
  3. Shove the brick into place, squeezing out mortar at the top of the joint.
  4. Cut off the excess mortar as shown in Figure 82

Figure 81 – Spreading mortar over brick face.

Figure 82 – Cutting off excess mortar.

To lay a closure brick in a header course:

  1. Spread about 1 inch of mortar on the sides of the brick already in place as shown in Figure 83.
  2. Spread about 1 inch of mortar on both sides of the closure brick as shown in Figure 84.
  3. Lay the closure brick carefully into position without disturbing the brick already laid as shown in Figure 85.

Figure 83 – Spreading mortar on sides of brick already laid.

Figure 84 – Spreading mortar on both sides of closure brick.

Figure 85 – Laying the brick into position.

If you do disturb any adjacent brick, cracks will form between the brick and mortar, allowing moisture to penetrate the wall. To place a closure brick for a stretcher course, use the same techniques as for a header course:

  1. Spread about 1 inch of mortar on the ends of the brick already in place as shown in Figure 86.
  2. Spread about 1 inch of mortar on both ends of the closure brick as shown in Figure 87.

Figure 86 – Spreading mortar on ends of brick already laid.

Figure 87 – Spreading mortar on both ends of closure brick.

  1. Lay the closure brick carefully into position without disturbing the brick already laid as shown in Figure 88.

Figure 88 – Laying the brick into position.

As mentioned earlier, filling exposed joints with mortar immediately after laying a wall is called pointing. You can also fill holes and correct defective mortar joints by pointing, using a pointing trowel.

4.8.0 Cutting Brick

Figure 89 – Cutting brick with a chisel.

To cut a brick to an exact line, you should use a chisel, as shown in Figure 89, or brick set. The straight side of the tool’s cutting edge should face both the part of the brick to be saved and the bricklayer. One mason’s hammer blow should break the brick. For extremely hard brick, first roughly cut it using the brick hammer head, but leave enough brick to cut accurately with the brick set.

Use a brick hammer for normal cutting work, such as making the closure bricks and bats around wall openings or completing corners. Hold the brick firmly while cutting it.

  1. Cut a line all the way around the brick using light hammerhead blows.
  2. A sharp blow to one side of the cutting line should split the brick at the cutting line, as shown in Figure 90.
  3. Trim rough spots using the hammer blade, as shown in Figure 91.

Figure 90 – Striking brick to one side of cutting line.

Figure 91 – Trimming rough spots.

4.9.0 Finishing Joints

The exterior surfaces of mortar joints are finished to make brick masonry waterproof and give it a better appearance. If joints are simply cut to the face of the brick and not finished, shallow cracks will develop immediately between the brick and the mortar. Always finish a mortar joint before the mortar hardens too much. Figure 92 shows several types of joint finishes, the most important of which are concave, flush, and weather.

Figure 92 – Joint finishes.

Of all joints, the concave is the most weather tight. After removing the excess mortar with a trowel, make this joint using a jointer that is slightly larger than the joint. Use force against the tool to press the mortar tightly against the brick on both sides of the mortar joint. The flush joint is made by holding the trowel almost parallel to the face of the wall while drawing its point along the joint.

A weather joint sheds water from a wall surface more easily. To make it, simply push downward on the mortar with the top edge of the trowel.

4.10.0 Arches

A well constructed brick arch can support a heavy load, mainly due to the way weight is distributed over its curved shape. There are two common arch shapes; Figure 93 shows an elliptical arch, and Figure 94 shows a circular arch. Brick arches require full mortar joints. The joint width is narrower at the bottom of the arch than at its top, but it should not narrow to less than 1/4 inch at any point. As laying progresses, make sure the arch does not bulge out of position.

Figure 93 – Elliptical arch

Figure 94 – Circular arch

4.10.1 Templet

It is obviously impossible to construct an arch without support from underneath. These temporary wooden supports must not only be able to support the masonry during construction but also provide the geometry necessary for the proper construction and appearance of the arch. Such supports are called templets.

Dimensions – Construct a brick arch over the templet, as shown in Figure 95, that remains in place until the mortar sets. You can obtain the templet dimensions from the construction drawings. For arches spanning up to 6 feet, use 3/4 inch plywood to make the templet. Cut two pieces to the proper curvature, and nail them to 2 by 4 spacers that provide a surface wide enough to support the brick.

Figure 95 – Using a templet to construct an arch.

Positioning – Use wedges to hold the templet in position until the mortar hardens enough to make the arch self supporting. Then drive out the wedges.

4.10.2 Layout

Lay out the arch carefully so that you don’t have to cut any bricks. Use an odd number of bricks so that the key, or middle, brick falls into place at the exact arch center, or crown. The key, or middle, brick is the last one laid. To determine how many bricks an arch requires, lay the templet on its side on level ground and set a trial number of bricks around the curve. Adjust the number of bricks and the joint spacing, not less than 1/4 inch, until the key brick is at the exact center of the curve. Then, mark the positions of the bricks on the templet and use them as a guide when laying the brick.

Test Your Knowledge

8. Modular U.S. brick are what nominal size?

A. 2 1/4 by 3 3/4 by 8 inches
B. 2 1/4 by 3 5/8 by 7 5/8 inches
C. 3 by 4 by 9 inches
D. 2 3/4 by 4 by 12 inches

9. When stacking brick, you should start tapering back when the pile reaches what minimum height?

A. 1 foot
B. 2 feet
C. 3 feet
D. 4 feet

10. To tie brick on the outside face of a wall to the backing course when no header courses are to be installed, what should you use?

A. Copings
B. Metal ties
C. Flashing
D. Rebar

11. For weathertightness, what is the best type of joint finish?

A. Flush
B. Bead
C. Concave
D. Weather

 

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Summary

Masonry is construction consisting of units held together with mortar, such as concrete block, stone, brick, clay tile products, and, sometimes, glass block. The characteristics of masonry work are determined by the properties of the masonry units and mortar and by the methods of bonding, reinforcing, anchoring, tying, and joining the units into a structure.

Masonry involves the use of a wide selection of tools and equipment, including trowels, chisels, hammers, and jointers.

One of the most common masonry units is the concrete block. There are all types of concrete block, both hollow and solid, made with any kind of aggregate. Concrete blocks are also available with applied glazed surfaces, various pierced designs, and a wide variety of surface textures.

Good workmanship is a very important factor in building masonry walls. It’s important to make every effort to lay each masonry unit plumb and true.

Brick masonry is construction in which uniform units called bricks, small enough to be placed with one hand, are laid in courses with mortar joints to form walls. Bricks are kiln baked from various clay and shale mixtures. The chemical and physical characteristics of the ingredients vary considerably. These characteristics and the kiln temperatures combine to produce brick in a variety of colors and hardnesses.

 

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Review Questions

1. To smooth cut a concrete masonry unit, use which of the following tools?

A. A mason’s hammer
B. A brick chisel
C. A brick trowel
D. A pointing trowel

2. To finish a masonry joint, use which of the following tools?

A. Trowel
B. Bolster
C. Mortar board
D. Jointer

3. When placing masonry units, use a steel square for which of the following jobs?

A. Leveling short columns
B. Laying out corners
C. Plumbing long stretches
D. Finishing joints

4.  There are three main types of concrete masonry units.

A. True
B. False

5. Load-bearing concrete block used in above and below grade exterior walls that may or may not be exposed to moisture should be what grade?

A. Grade M
B. Grade N
C. Grade O
D. Grade S

6. A standard concrete masonry unit made with pumice has what approximate weight?

A. 20 to 30 pounds
B. 25 to 35 pounds
C. 35 to 45 pounds
D. 45 to 55 pounds

7. The sides and the recessed ends of a concrete block are called the

A. Shell
B. Face shell
C. Edge
D. Web

8.  Spreading a 1 inch layer of mortar on both bed joints of walls and columns is called face shell mortar bedding.

A. True
B. False

9. For above grade exposed masonry where high compressive and lateral strength is not required, use what type of mortar?

A. Type M
B. Type N
C. Type O
D. Type S

10. You should not temper mortar that has been mixed longer than what maximum time?

A. 1 hour
B. 2 1/2 hours
C. 3 hours
D. 4 1/2 hours

11.  You should only add calcium chloride should to mortar if it is specified in the specifications.

A. True
B. False

12. Using standard block, how many courses are required for a concrete block wall 10 feet high?

A. 14
B. 15
C. 16
D. 17

13. To lay 600 square feet of wall, you need approximately how many (a) 8 by 4 by 12 inch concrete blocks and (b) cubic feet of mortar?

A. (a) 520 (b) 15
B. (a) 680 (b) 15
C. (a) 770 (b) 24
D. (a) 900 (b) 24

14. How many cubic feet of sand are required to complete a 1:2 mix for 2 cubic yards of mortar?

A. 26
B. 51
C. 52
D. 104

15. When bags of cement or lime are stacked on pallets, a setback should begin at what tier?

A. Eighth
B. Sixth
C. Fifth
D. Fourth

16. A concrete block should be laid with what portion up?

A. The narrow end of the face shell
B. The web facing
C. The end shell
D. The thicker end of the face shell

17. What part(s) of a block wall is/are laid immediately after the first courses?

A. Corners
B. Second course
C. Lintels
D. Lateral supports

18. During the construction of a concrete block wall, you must butter all vertical edges of a block at what point?

A. When the corner blocks are being placed
B. When the closure block is being installed
C. When all stretchers are placed
D. When the second course is being laid

19. To ensure weathertight joints, at what point in construction should you start tooling mortar joints?

A. Immediately after laying each course
B. As soon as the mortar becomes thumbprint hard
C. After the excess mortar falls off the block
D. At the end of the workday

20. Any excess mortar remaining on a concrete block after the joints are tooled should be removed by what method?

A. Rubbing with a burlap bag
B. Flushing with water
C. Striking the mortar with a small jointer
D. Rubbing with a piece of broken concrete

21. The insertion of roofing felt in the end core of the concrete block in a control joint serves what purpose?

A. It permits the wall to move without cracking
B. It eliminates bonding of the mortar on both sides of the joint
C. It prevents raking of the outside block
D. It eliminates bonding of the mortar on one side of the joint

22. Intersecting bearing walls should be tied together by what means?

A. Masonry bonds in alternate courses
B. Hardware cloth placed across the courses
C. Metal tie bars bent at right angles
D. Anchor bolts located in alternate courses

23. Lintel blocks should extend past the edge of an opening to what minimum distance?

A. 6 in
B. 12 in
C. 16 in
D. 20 in

24. When reinforcing a block wall, you can ensure proper alignment of the rebar by performing what action?

A. Placing a cleanout block at every stud in all courses
B. Pouring concrete as each course is laid
C. Placing a cleanout block at every stud in the first course
D. Pouring concrete around the rebar as it is placed

25.  Weep holes in retaining walls are used to prevent water accumulation behind the wall.

A. True
B. False

26. The backing course for a cavity wall should be made with what type of brick?

A. Face
B. Building
C. Glazed
D. Fire

27. Where cleanliness and ease of cleaning are necessary, what type of brick should you use?

A. Face
B. Cored
C. Glazed
D. Sand-lime

28. For masonry structures that can withstand high temperatures without cracking or decomposing, you should use what type of brick?

A. Cored
B. Press
C. Clinker
D. Fire

29.  In masonry, a soldier is a row lock brick laid with its bed parallel to the face of the wall.

A. True
B. False

30. In brick walls, structural bonding takes place by what means?

A. Adhesion of grout to adjacent wythes of masonry
B. Metal ties embedded in connecting joints
C. Interlocking the masonry units
D. All of the above

31. The pattern formed by the masonry units and mortar joints on the face of a wall is called what type of bond?

A. Stack
B. Pattern
C. English
D. Running

32. Which of the following bonds is a variation of the running bond in which a header course appears at the fifth, sixth, or seventh course?

A. Running
B. Flemish
C. Common or American bond
D. Dutch bond

33. You must place a three-quarter brick at the corner of each header course in which of the following pattern bonds?

A. Common
B. English
C. Block
D. Stacked

34. Moisture is prevented from seeping under a horizontal masonry surface by the installation of

A. Sills
B. Copings
C. Parapets
D. Flashing

35. Water that accumulates on a flashing should be allowed to drain to the outside by what means?

A. Parapets
B. Concealed flashing
C. Weep holes
D. Sills

36. To ensure a good bond between mortar and brick, avoid which of the following joints?

A. Slushed
B. Bed
C. Cross
D. Header

37. Spread bed joint mortar what maximum number of bricks ahead?

A. 5
B. 7
C. 9
D. 11

38. For which of the following reasons should you form a shallow furrow in the mortar of a bed joint?

A. To maintain the required width of brick spacing
B. To conserve mortar
C. To keep a gap from forming and allowing water to enter the wall
D. To allow the mortar to dry slightly before placing the brick

39. To cut a brick to an exact line with a brick chisel or brick set, follow which of the following procedures?

A. Break the brick with one blow of the hammer
B. Let the straight side of the cutting edge face you
C. Let the straight side of the cutting edge face the part of the brick that is to be saved
D. All of the above

40.  When laying out a brick arch, you can make the key brick line up by using an even number of bricks.

A. True
B. False
 

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