SECTION III. BRICK CONSTRUCTION
9-38. The bricklayer actually lays the brick and is responsible for laying out the job so that the finished masonry has the proper quality and appearance. In wall construction, the bricklayer must make sure that the walls are plumb and the courses are level.
9-39. The bricktender mixes mortar and carries brick, mortar, and supplies material to the bricklayer, as needed. The bricktender fills the mortar board and places it in a convenient spot for the bricklayer. He assists in layout and rapid backup bricklaying by laying out bricks in a line on an adjacent course so that the bricklayer only has to move each brick a few inches to lay them. He also wets brick during warm weather. There are four reasons why bricks must be wet just before laying them:
A better bond is created between the brick and the mortar.
Dust and dirt are washed from the brick surfaces because mortar adheres better to a clean brick.
Mortar spreads more evenly under a wet brick surface.
Dry brick absorbs water from the mortar rapidly, particularly portland-cement mortar. To harden properly, cement requires sufficient moisture to complete the hydration process. Therefore, if the brick absorbs too much water from the mortar, the cement will not harden properly.
9-40. A qualified engineer must determine actual footing width and thickness for high walls and walls that will carry a heavy load. A footing must rest below the frost line to prevent foundation heaving and settlement.
9-41. A wall requires a footing when the supporting soil cannot withstand the wall load without a further means of load redistribution. The footing must be wider than the wall thickness as shown in Figure 9-19. For an ordinary one- story building having an 8-inch-thick wall, a footing 16 inches wide and approximately 8 inches thick is usually large enough. Although brick masonry footings are satisfactory, footings are normally made from concrete leveled on top to receive the brick or stone foundation walls. After preparing the subgrade, place a mortar bed about 1 inch thick on the subgrade to compensate for all irregularities. Lay the first course of the foundation on the mortar bed followed by succeeding courses (see Figure 9-19).
Figure 9-19. Laying a wall footing
9-42. Figure 9-20 shows a footing for a 12 by 16-inch brick column. This footing requires the same construction method as the wall footing.
Figure 9-20. Column footing
LAYING AN 8-INCH COMMON-BOND BRICK WALL
9-43. You can build both solid and hollow walls from brick masonry. The solid 8- and 12-inch walls in common bond are the most familiar ones in the US.
LAYING OUT THE WALL
9-44. To build a wall of a given length, adjust the width of the head joints so that a particular number of bricks or a particular number plus a half-brick will equal the given length. To do this use the following steps:
Step 1. Lay out the bricks for the foundation without mortar first, as shown in Figure 9-21.
Figure 9-21. Determining number of bricks in one course and head-joint widths
Step 2. Space them equally. The distance between them will equal the thickness of the head joints. Tables 9-2, 9-3, and 9-4 below give the number of courses in a wall of a given height using standard brick and different joint widths.
Table 9-2. Height of course using 2 1/4-inch brick, 3/8 inch joint
Table 9-3. Height of course using 2 1/4-inch brick, 1/2-inch joint
Table 9-4. Height of course using 2 1/4-inch brick, 5/8-inch joint
LAYING CORNER LEADS
9-45. The following steps should be used in laying the corner leads:
9-46. Normally, the first course is a header course. Step 1 of Figure 9-22 below shows how to start laying a corner lead.
Figure 9-22. Laying first course of corner lead for 8-inch common-bond brick wall
Step 1. Lay a 1-inch mortar bed on the foundation.
Step 2. Cut two three-quarter closures and press one into the mortar bed until it makes a bed joint 1/2 inch thick (see a in step 2 of Figure 9-22.
Step 3. Spread mortar on the end of the second three-quarter closure and form a 1-inch thick head joint as described in paragraph 9-29 (see b in step 2 of Figure 9-22).
Step 4. Cut off the mortar that squeezes out of the joints.
Step 5. Lay a mason's level in the two positions shown in step 2 of Figure 9-22, and check the levels of the two three-quarter closures. The exterior edges of both closures must be flush with the exterior face of the foundation.
Step 6. Spread mortar on one bed of a whole brick (see c in step 3 of Figure 9-22) and lay it as shown.
Step 7. Check its level using the mason's level in the positions shown in step 3 of Figure 9-22. The end of this brick must also be flush with the exterior face of the foundation.
Step 8. After laying this brick in the proper position, cut the quarter closures e and f, and lay them as described in paragraph 9-34, for laying closure bricks.
Step 9. Remove all excess mortar and check the tops of the quarter closures to make sure that they are flush with bricks a and b.
Step 10. Spread mortar on brick g (see step 4 of Figure 9-22), shove it into position as shown, and remove any excess mortar.
Step 11. Lay bricks h, i, j, and k the same way. Check their levels by placing the mason's level in the positions shown in step 4 of Figure 9-22. All brick ends must be flush with the foundation surface.
Step 12. Lay bricks l, m, n, o, and p in the same manner (see step 5 of Figure 9-22). You must lay 12 header bricks in the first course of the corner lead--six bricks on each side of the three-quarter closures a and b.
9-47. Lay the second course of the corner lead (a stretcher course) as shown in steps 1 and 2 of Figure 9-23 below.
Figure 9-23. Laying second course of corner lead for 8-inch common-bond brick wall
Step 1. Spread a 1-inch mortar bed over the first course and make a shallow furrow in it.
Step 2. Push brick (a) (see step 2 of Figure 9-23) into the mortar bed until it makes a joint 1/2 inch thick.
Step 3. Spread mortar on the end of the brick and shove it into place. Remove the excess mortar and check the joints for thickness.
Step 4. Lay bricks c, d, e, f, and g the same way. Check them by placing the mason's level in the position shown in step 2 of Figure 9-23 to make sure they are level.
Step 5. Plumb the corners in several places by placing the mason's level in the vertical position as shown in Figure 9-24 below. As step 3 of Figure 9-23 shows, the second course requires seven bricks.
Figure 9-24. Plumbing a corner
Step 6. Lay the remaining bricks in the corner lead as you did the bricks in the second course.
9-48. It is not good practice to move brick after it is laid in the mortar. Take great care to place the bricks accurately the first time. Be sure to finish or tool the joints before the mortar sets.
Step 1. Lay the portion of the wall between the leads using the leads as a guide.
Step 2. Check the level of the lead courses continuously.
Step 3. Plumb the lead after laying the first few courses. If the masonry is not plumb, move the bricks either in or out until the lead is exactly plumb.
Opposite Corner Leads
9-49. Build the opposite corner lead the same way. Make sure that the tops of corresponding courses are the same level in each lead. For example, the top of the second course in one corner lead must be the same height above the foundation as the second course in the opposite corner. Mark a long 2-by 2-inch pole with the correct course heights above the foundation, and then use it to check the course height in the corner leads as you build them.
LAYING THE FACE TIER BETWEEN THE CORNER LEADS
9-50. Use a line, as shown in Figure 9-25 to lay the face tier of brick for the wall between the leads.
Figure 9-25. Using a line to lay face tier of brick between corner lead
Step 1. Drive nails into the top of the cross joints.
Step 2. Attach the line to the nail in the left-hand lead, pull it taut, and attach it to the nail in the right-hand lead. Position the line 1/16 inch outside the wall face, level with the top of the brick. It is better to use a tool called a line pin that resembles a triangular-shaped nail to attach the line at the right-hand or pull end. The line pin prevents the taut line from unwinding.
Step 3. Lay the first or header course in between the two corner leads as described in paragraph 9-46, when the line is in place.
Step 4. Push the brick into position with its top edge 1/16 inch behind the line. Be sure not to crowd the line. If the corner leads are built accurately, the entire wall will be level and plumb. You need not use a mason's level continually when laying the wall between the leads, but check it occasionally at several points.
Step 5. Move the line to the top of the next mortar joint for the second or stretcher course.
Step 6. Lay the stretcher course as described in paragraph 9-47, and finish the face joints before the mortar hardens.
Step 7. Lay the face tier of the wall between the leads up to, but not including, the second header course (normally five stretcher courses). Then lay the backup tier.
LAYING THE BACKUP TIER BETWEEN THE CORNER LEADS
9-51. Lay the backup brick for the corner leads first, as shown in Figure 9-26, followed by the remaining brick. For an 8-inch wall, you do not need to use a line for the backup brick as you do in a 12-inch wall. After laying the backup tier up to the height of the second header course, lay the second header course in the face tier.
Figure 9-26. Laying backup brick for the corner lead of an 8-inch common bond brick wall
9-52. When the wall for the entire building is laid up to a height that includes the second header course, continue laying the corner leads up six more courses. Then construct the wall between the leads as described above. Repeat the entire procedure until the wall is laid to the required height.
LAYING A 12-INCH COMMON-BOND BRICK WALL
9-53. Figure 9-27 below shows how to lay the first three courses of a 12-inch common bond-brick wall. Note that the construction is similar to that of an 8-inch wall, except that it includes a second tier of backup brick (see view 3 of Figure 9-27).
Figure 9-27. Laying a 12-inch common-bond brick wall
Step 1. Lay two overlapping header courses first (see view 1 of Figure 9-27), and build the corner leads.
Step 2. Lay the two tiers of backing brick, using a line for the inside tier.
Step 3. Lay the second course as shown in view 2 of Figure 9-27, and the third course as shown in view 3 of Figure 9-27.
PROTECTING WORK INSIDE WALLS
9-54. Each night cover the tops of all work completed inside the brick walls to protect them from weather damage. Use the boards or tarpaulins secured by loose bricks.
USING A TRIG
9-55. When building a long wall, erect a third lead between the corner leads. Then stretch a line from the left-hand lead to the middle lead to the right-hand lead. Now use a trig to keep the line from sagging or being windblown toward or away from the wall face. A trig (see Figure 9-28) is a second short piece of line that loops around the main line and fastens to the top edge of a previously laid brick in the middle lead. A piece of broken brick rests on top of the trig to hold it in position.
Figure 9-28. Use a trig to support the line when building a long wall
CONSTRUCTING WINDOW AND DOOR OPENINGS
9-56. You must plan ahead when laying any wall containing windows, making sure to leave openings of the correct size as the bricklaying proceeds.
9-57. Procedures to use when constructing window openings are as follows:
Planning. First, find out the specified distance from the foundation to the bottom of the window sill. The height of the wall to the top of a full course must equal that distance. Now, calculate how many courses will bring the wall up to that height. For example, if the sill is 4 feet 4 1/4 inches above the foundation using 1/2-inch mortar joints, you must lay 19 courses before you reach the bottom of the sill. Calculate it this way: each brick plus one mortar joint equals 2 1/4 plus 1/2 equals 2 3/4 in per course, and 4 feet 4 1/4 inches divided by 2 3/4 inches equals 19 courses.
Marking. Lay the corner leads and the wall in between them so that the top of the last course is not more than 1/4 inch above the top of the window frame. Use a pencil to mark the top of each course on the window frame itself. If the mark for the top of the last course does not come out to the proper level, change the joint thickness you plan to use until it does.
Laying the brick. Lay the corner leads with joints of the calculated thickness. When the corner leads are built, install a line as described earlier and stretch it across the bottom of the window openings. Lay the brick for the wall between the leads up to sill height using the calculated joint thickness. If the window openings are planned properly, you can lay the face tier brick with a minimum of cutting.
Laying the rowlock sill course. When the wall reaches sill height, lay the rowlock sill course as shown in Figure 9-29 below. Pitch the course downward away from the window. The rowlock normally takes up a vertical space equal to two courses of brick. Finish the exterior joint surfaces carefully to make them watertight.
Placing the frame. As soon as the mortar sets, place the window frame on the rowlock sill course, bracing it firmly until the masonry reaches about ingathered of the way up the frame. (But do not remove the braces for several days so that the wall above the window frame sets properly). Now lay the rest of the wall around the frame until the top of the last course is not more than 1/4 inch above the window frame
Figure 9-29. Constructing a window opening
9-58. Use the same procedure to construct a door opening (see Figure 9-30) as for a window opening. To anchor the door frame to the masonry using screws or nails, cut pieces of wood to the size of a half closure and lay them in mortar the same as brick. Place the wood blocks at several points along the top and sides of the door opening.
Figure 9-30. Constructing a door opening
9-59. The lintel above a window or door carries the weight of the wall above it. It rests on top of the last brick course that is almost level with the top of the window or door frame, and its sides bed firmly in mortar. Close any space between the window or door frame and the lintel with blocking, and weather-strip it with bituminous materials. Then continue the wall above the window or door when the lintel is in place.
9-60. Lintels are made from steel, precast reinforced-concrete beams, or wood. Do not use wood lintels if possible. In reinforced brick masonry, properly installed steel reinforcing bars support the brick above wall openings.
9-61. The placement and relative positioning of lintels are determined by both the wall thickness and the type of window or door specified. This information is usually on the building drawings. If the lintel size is not specified, Table 9-5 gives size and quantities of double-angle steel and wood lintels to use for various opening widths in both 8- and 12-inch walls. Figures 9-31 and 9-32 below show how to place different kinds of lintels in different wall thickness. Figure 9-31 shows how to install a doubleness steel lintel in an 8-inch wall. The angle is 1/4-inch thick, which allows the two angle legs that project up into the brick to fit exactly into the 1/2-inch joint between the face and backing ties.
Table 9-5. Lintel sizes for 8-inch and 12-inch walls
Figure 9-31. Installing a double-angle steel lintel in an 8-inch wall
Figure 9-32. Installing lintels in a 12-inch wall
9-62. Corbeling consists of brick courses projecting beyond the wall face to increase its thickness or form a self-supporting shelf or ledge (see Figure 9-33). The portion of a chimney exposed to weather is frequently corbeled to increase its thickness for better weather resistance. Corbeling usually requires various-sized bats ( a broken brick with one end whole, the other end broken off). Use headers as much as possible, but the first projecting course can be a stretcher course if necessary. No course should extend more than 2 inches beyond the course underneath it, and the total corbel projection should not be greater than the wall thickness.
Figure 9-33. Constructing a corbeled brick wall
9-63. Corbel construction requires good workmanship for maximum strength. Make all mortar joints carefully and fill them completely with mortar. When the corbel must withstand large loads, consult a qualified engineer.
9-64. A well-constructed brick arch can support a heavy load, mainly due to its curved shape. Figure 9-34 shows two common arch shapes.
Figure 9-34. Common shapes
Brick arches require full mortar joints. Note that 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 that the arch does not bulge out of position.
BUILDING A TEMPLET
9-65. Construct a brick arch over a temporary wood support called a templet (see Figure 9-35) that remains in place until the mortar sets.
Figure 9-35. Using a templet to construct an arch
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 2 spaces that provide a surface wide enough to support the brick. Use wedges to hold the templet in position until the mortar hardens enough to make the arch self-supporting. Then drive out the wedges.
LAYING OUT THE ARCH
9-66. Lay out the arch carefully to avoid cutting the brick. 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. Mark the positions of the bricks on the templet and use them as a guide when laying the brick.
9-67. Water does not usually penetrate brick walls through the mortar or brick, but through cracks between the brick and the mortar. Cracks are more likely to occur in head joints than in bed joints.
9-68. Sometimes a poor bond between the brick and the mortar causes cracks to form and sometimes mortar shrinkage is responsible. Do not change the position of a brick after the mortar begins to set, because this destroys the bond between the brick and mortar and a crack will result. Wet high-suction bricks and other bricks as necessary during hot weather so that they do not absorb too much moisture from the mortar and cause it to shrink. You can reduce both the size and number of cracks between the mortar and the brick by tooling the exterior faces of all mortar joints to a concave finish. To obtain watertightness, completely fill all head and bed joints with mortar.
9-69. Figure 9-36 shows a good way to produce a watertight wall called parging or back plastering. Parging means to plaster the back of the brick in the face tier with not less than 3/8 inch of rich cement mortar before laying the backing bricks. Because you cannot plaster over mortar protruding from the joints, first cut all joints flush with the back of the face tier.
Figure 9-36. Parging the back of the face tier for watertightness
WATERPROOF WITH MEMBRANES
9-70. If a wall is subject to much water pressure, use a membrane to waterproof it. A properly installed membrane adjusts to any shrinkage or settlement without cracking.
9-71. If the wall is subject to much groundwater, or the surrounding soil does not drain well, construct tile drains or French drains around the wall base (see Figure 9-37). If drainage tile is not available, an 8-inch layer of coarse loose rock or stone will do the job. This is called a French drain.
Figure 9-37. Draining a wall around its foundation
9-72. Before applying waterproof or portland-cement paints, repair all cracks. To repair mortar joint cracks, first chip out the mortar around the full width of the crack to a depth of about 2 inches. Carefully scrub the hole with clean water. While the hole surfaces are still wet, apply a coating of cement mortar made with enough water to form a thick liquid. Before the coating sets, fill the hole with prehydrated mortar, which is recommended for tuck-pointing in paragraph 9-90.
NOTE: Repair cracks in bricks the same way as cracks in concrete (see paragraphs 5-95 and 5-105).
USING WATERPROOF COATING
9-73. Walls can be waterproofed in three ways:
Bituminous mastic. To make a below-grade foundation wall watertight, apply two coats of bituminous mastic to the exterior brick surface. You can apply asphalt or coal tar pitch using a mop.
Waterproof paints. You can improve the watertightness of above-grade brick walls by applying a transparent, waterproof paint, such as a water solution of sodium silicate. Varnish, certain white and color waterproof paints, and high-quality oil-base paints are also effective. Apply them according to the directions.
Portland-cement paint. This paint generally gives excellent results if you apply it when the wall is at least 30 days old. Use type 2, class A portland-cement paint and follow the manufacturer's instructions for mixing and applying it. Remove all efflorescence from the surface (see paragraph 9-95) and dampen the surface with a water spray before applying the paint. Use white-wash or calcimine-type brushes or a spray gun, but spraying reduces the paint's rain resistance.
9-74. To line furnaces, incinerators, and so forth, use fire-resistant brick to protect the supporting structure or outer shell from intense heat. The outer shell probably consists of common brick or steel, neither of which has good heat resistance.
9-75. The two types of fire-resistant brick are fire bricks and silica bricks.
Fire bricks are made from a special clay, called fire clay, or that withstand higher temperatures and are heavier and usually larger than common brick. Their standard size is 9 by 4 1/2 by 2 1/2 inches.
Silica bricks resist acid gases; however, do not use silica brick if it will be alternately heated and cooled. Therefore, you should line most incinerators with fire brick rather than with silica brick.
LAYING FIRE BRICK
9-76. Fire brick requires thin mortar joints, especially if the brick is subject to such high temperatures as those in incinerators. Store the bricks in a dry place until you use them.
9-77. Use a mortar made from fire clay and water mixed to the consistency of thick cream. Obtain fire clay by grinding used fire brick.
9-78. To lay fire bricks, use the following proedures:
Step 1. Dip the brick in the mortar, covering all surfaces except the top bed.
Step 2. Lay the brick and tap it firmly into place with a bricklayer's hammer.
Step 3. Make the mortar joints as thin as possible, and fit the bricks together tightly. Remember that any heat that migrates through the cracks between the fire bricks will damage the outside shell of the incinerator or furnace.
Step 4. Stagger the head joints the same way you do in ordinary brick construction. The bricks in one course should lap those in the course underneath by one-half brick.
LAYING SILICA BRICK
9-79. Lay silica bricks without mortar, fitting them so close together that they fuse at the joints at high temperatures. Stagger the head joints as you do in ordinary brick construction.
TYPES OF WALLS
9-80. The basic types of walls are: hollow and partition.
9-81. Hollow walls consist of an inner and an outer wythe separated by an air space. The two most important types of hollow walls are the cavity wall and the rowlock wall. Partition walls divide the interior space in a one-story building. They may be load-bearing or nonload-bearing walls.
9-82. A cavity wall is a watertight wall that can be plastered without furring or lathing. It looks the same on the exterior as a solid wall without header courses (see Figure 9-38). Instead of headers, metal ties are installed every sixth course on a 24-inch center that holds the two tiers together. To prevent water penetration to the inner tier, angle the ties downward from the inner to outer tier. A 2-inch cavity or air space between the two brick wythes drains any water that penetrates the outer tier. The air space also provides good heat and sound insulation. The bottom of the cavity is above ground level. It is drained by weep holes in the vertical joints in the first course of the exterior tier. Make the weep holes simply by leaving the mortar out of the joint. Space them about a 24-inch interval.
Figure 9-38. Construction details of a cavity wall
9-83. A rowlock is a header laid on its face or edge. A rowlock also has a 2-inch cavity between the wythes as shown in Figure 9-39. In this type of rowlock wall, the face tier is loose like a common-bond wall having a full header course every seventh course. However, the bricks in the inner or backing tier are laid on edge. A header course ties the outer and backing ties together. For an all-rowlock wall, lay the brick on edge in both the inner and outer tiers. Install a header course every fourth course (that is, three rowlock courses to every header course). The rowlock wall is not as watertight as the cavity wall, because water will follow along any crack in the header course and pass through to the interior surface.
Figure 9-39. Construction details of a rowlock wall
9-84. A partition wall that carries very little load requires only one wythe producing a wall 4 inches thick. You can lay a wall of this thickness without headers.
LAYING HOLLOW AND PARTITION WALLS
9-85. Lay the brick for hollow and partition walls as described starting in paragraph 9-29 for making bed joints (f), head joints (h), cross joints (j), and closures (K and l). Use a line the same as for a common bond wall. Erect the corner leads first, and then build the wall between them.
9-86. Sewer systems require manholes (see Figure 9-40) for cleaning and inspection. The manhole size largely depends on the sewer size. Manholes are either circular or oval to reduce the stresses from both water and soil pressures. A 4-foot diameter manhole is satisfactory for small, straight-line sewers. Construction details of a typical manhole are shown in view 2 of Figure 9-40. Although both the bottom and walls of a manhole are sometimes made from brick, the bottom is normally made from concrete because it is easier to cast in the required shapes. However, you can construct the walls more economically from brick, because it requires no form work.
Figure 9-40. Construction details of a sewer manhole
9-87. The wall thickness of a manhole depends on its depth and diameter. You can use an 8-inch wall for manholes up to 8 feet in diameter and less than 15 feet deep. A qualified engineer should design any manholes over 15-feet deep.
9-88. Use only headers for an 8-inch wall, but no line. Use a mason's level to make sure that all bricks in a particular course are level. Span the manhole with a straightedge or place a mason's level on a straight surfaced 2 by 4 across the manhole, to make sure the brick rises to the same level all around. Because the wall appearance is not important, some irregularities in both brick position and mortar joint thickness are permissible. All joints should be either full or closure joints.
Laying the first course. Place a 1-inch mortar bed on the foundation. Lay the first course on the mortar bed, followed by the succeeding header courses.
Corbeling. To reduce the manhole diameter to fit the frame and cover, corbel the brick inward as shown in view 2 of Figure 9-40 above. No brick should project more than 2 inches beyond the brick underneath it. Space the wrought-iron steps about every 15 inch vertically, and embed them in a cross mortar joint. When complete, plaster the wall on the outside at least 3/8-inch thick with the same mortar used in laying the brick.
Placing. Spread a 1-inch mortar bed on top of the last course, and place the base of the manhole frame in the bed.
SUPPORTING BEAMS ON A BRICK WALL
9-89. The following beams are used on brick walls.
Wood Beams. Figure 9-41 shows how to support a wood beam on a brick wall. Note the wall tie. Keep mortar away from the beam as much as possible, because wood can dry rot when completely encased in mortar. Protect the beam with a beam box (see Figure 9-41). Cut the end of the beam at an angle so that, in case of fire, it will fall without damaging the wall above the beam. For an 8- or 12-inch wall, let the beam bear on the full width of the inside tier.
Steel Beams. When a brick wall must support a steel beam, insert a steel bearing plate set in mortar under the beam. A properly designed bearing plate prevents the beam from crushing the brick. The size of the bearing plate depends on the size of the beam and the load it carries.
Figure 9-41. Supporting a wood beam on a brick wall
MAINTAINING AND REPAIRING BRICK WALLS
9-90. A well-constructed brick masonry wall requires little maintenance or repair. It can be more expensive to repair old masonry properly than to completely remove and replace just the disintegrated portion. Good mortar, proper joint finishing, and adequate flashing add little to the initial cost, but reduce maintenance cost throughout the life of the masonry.
9-91. Tuck-pointing during routine maintenance means to cut out all loose and disintegrated mortar to a depth of at least 1/2 inch and replace it with new mortar. Use a chisel having a cutting edge about 1/2 inch wide. To stop leakage, cut out all the mortar in the affected area, and replace it with new mortar.
PREPPING THE MORTAR JOINT
9-92. After cutting out the defective mortar, remove all dust and loose material with a brush or a water jet. If you use a water jet, no further joint wetting is required. If not, moisten the joint surfaces.
PREPARING MORTAR FOR TUCK-POINTING
9-93. Use portland-cement-lime prehydrated Type S mortar or prehydrated prepared mortar made from type II masonry cement. Prehydrating mortar greatly reduces the amount of shrinkage. Mix the dry ingredients with just enough water to produce a damp mass of a consistency that retains its form when you compress it into a ball with your hands. Allow the mortar to stand for at least 1 hour, but not more than 2 hours. Then mix the mortar with enough water to produce a stiff, but workable consistency.
FILLING THE JOINT
9-94. Filling a joint with mortar is called repointing and is done with a pointing trowel. Before filling the joint, allow the moisture used in preparing the joint to absorb. Then pack the prepared prehydrated mortar into the joint tightly in thin layers about 1/4 inch thick, and finish them to a smooth concave surface using a pointing tool. Push the mortar into the joint in one direction only from the starting point, using a forward motion to reduce the risk of forming air pockets.
CLEANING NEW BRICK AND REMOVING STAINS
9-95. A skilled bricklayer can build a masonry wall that is almost free from mortar stains. However, most new brick walls still need some cleaning.
Step 1. Remove large mortar particles adhering to brick with a putty knife or chisel. Remove mortar stains with an acid solution of one part commercial muriatic acid to nine parts water. Acid must be poured into the water, not the water into the acid. Before applying the acid, thoroughly soak the masonry surface with water to prevent the stain from being drawn into the brick pores.
Step 2. Apply the acid solution with a long-handled stiff-fiber brush. Take all precautions to prevent the acid from getting on your hands, arms, or clothing, and wear goggles to protect your eyes. Protect door and window frames. Scrub an area of 15 to 20 square feet with the acid solution, and then wash it down immediately with clear water. Make sure that you remove all acid before it can attack the mortar joints.
Step 3. Removing any efflorescence. Efflorescence is a white deposit that forms on the surface of brick walls. It consists of soluble salts leached from the brick by penetrating water that dissolves the salt in the brick. When the water evaporates, the salt remain. Because efflorescence requires the presence of both water and salts, proper brick selection and a dry wall will keep it to a minimum. However, if simply scrubbing the wall with water and a stiff brush does not remove the efflorescence, you can remove it with the acid solution described above for cleaning new masonry.
CLEANING OLD BRICK
9-96. The principal ways to clean old brick masonry are sandblasting, steam cleaning with water jets, or using cleaning compounds. The type of brick and the nature of the stain will determine which method you use. Many cleaning compounds that do not affect the brick will damage the mortar. Rough-textured brick is more difficult to clean than smooth-textured brick.
Sometimes you cannot clean rough-textured brick without removing part of the brick itself, which changes the appearance of the wall.
9-97. Sandblasting consists of using compressed air to blow hard sand through a nozzle against a dirty surface, thereby removing enough of the surface to eliminate the stain. Place a canvas screen around the scaffold to salvage most of the sand. The disadvantage of sandblasting is that it leaves a rough-textured surface that collects soot and dust. Moreover, sandblasting usually cuts so deeply into the mortar joints that you may have to repoint them. After sandblasting, apply a transparent waterproofing paint to the surface to help prevent future soiling by soot and dust. Never sandblast glazed surfaces.
STEAM CLEANING WITH WATER JETS
9-98. Steam cleaning means to project a finely divided spray of steam and water at high velocity against a dirty surface. This removes grime effectively without changing the surface texture, which gives steam cleaning an advantage over sandblasting.
Equipment. Use a portable, truck-mounted boiler to produce the steam at a pressure ranging from 140 to 150 psi. Each cleaning nozzle requires about a 12-horse-power boiler. The velocity of the steam and water spray as it strikes the surface is more important than the volume of the spray.
Procedure. Use one garden hose to carry water to the cleaning nozzle and another to supply rinse water. Experiment to determine the best angle and distance from the wall to hold the nozzle. Adjust the steam and water valves until you obtain the most effective spray. Pass the nozzle back and forth over no more than a 3-square-feet area at one time. Rinse it immediately with clean water before moving to the next area.
Additives. To aid cleaning action, add sodium carbonate, sodium bicarbonate, or trisodium phosphate to the water entering the nozzle. Reduce a lot of the salt or efflorescence remaining on the surface by washing it down with water before and after steam cleaning.
Hand tools. Use steel scrapers or wire brushes to remove any hardened deposits that remain after steam cleaning. Be careful not to cut into the surface. After removing the deposits, wash down the surface with water and steam and clean it again.
9-99. You can use one of several cleaning compounds, depending on the nature of the stain. Most cleaning compounds contain salts that will cause efflorescence if the cleaning solution penetrates the surface. You can prevent this by thoroughly wetting the surface before applying the solution. You can remove whitewash, calcimine, or paint coatings with a solution of one part acid to five parts water. Use fiber brushes to scrub the surface with the solution while it is still foaming. After removing the coating, wash down the wall with clean water until you remove the acid completely.
9-100. Apply paint remover with a brush to remove oil paint, enamels, varnishes, shellacs, or glue sizing. Leave the remover on until the coating is soft enough to scrape off with a putty knife. The following are effective paint removers:
Commercial. When using commercial paint removers, the manufacturer's instructions should be followed.
Chemical. Use a solution of 2 pounds of trisodium phosphate in 1 gallon of hot water. Another solution is 1 1/2 pounds of caustic soda in 1 gallon of hot water.
Blasting and torching. Sandblasting or burning off with a blowtorch will also remove paint.
REMOVING MISCELLANEOUS STAINS
9-101. The following are procedures for removing different types of stains:
Iron stains. Mix seven parts lime-free glycerin into a solution of one part sodium citrate in six parts lukewarm water. Add whiting or kieselguhr to make a thick paste and apply it to the stain with a trowel. Scrape off the paste when it dries. Repeat the procedure until the stain disappears; then, wash down the surface with water.
Tobacco stains. Dissolve 2 pounds of trisodium phosphate in 5 quarts of water. Next, in an enameled pan, mix 12 ounces of chloride of lime in enough water to make a smooth thick paste. Then mix the trisodium phosphate with the lime paste in a 2-gallon stoneware jar. When the lime settles, draw off the clear liquid and dilute it with an equal amount of water. Make a stiff paste by mixing the clear liquid with powdered talc, and apply it to the stain with a trowel followed by washing the surface.
Smoke stains. Apply a smooth, stiff paste made from trichlorethylene and powdered talc. Cover the container when you are finished to prevent evaporation. If a slight stain still remains after several applications, wash down the surface and then follow the procedure described above for removing tobacco stains. Use the paste only in a well-ventilated space because its fumes are harmful.
Copper and bronze stains. Mix one part ammonium chloride (salammoniac) in dry form to four parts powdered talc. Add ammonia water and stir the solution to obtain a thick paste. Apply the paste to the stain with a trowel, and allow it to dry. Several applications may be necessary. Then wash down the surface with clear water.
Oil stains. Make a solution of 1 gallon trisodium phosphate to 1 gallon of water, adding enough whiting to form a paste. Trowel the paste over the stain in a layer 1 1/2 inch thick, and allow it to dry for 24 hours. Remove the paste and wash down the surface with clean water.
9-102. Flashing is an impermeable membrane placed in brick masonry at certain locations to exclude water or to collect any moisture that penetrates the masonry and direct it to the wall exterior. Flashing can be made from copper, lead, aluminum, or bituminous roofing paper. Copper is best, although it stains the masonry as it weathers. Use lead-coated copper if such staining is unacceptable. Bituminous roofing papers are cheapest, but not as durable. They will probably require periodic replacement in permanent construction, and their replacement cost is greater than the initial cost of installing high-quality flashing. Corrugated copper flashing sheets produce a good bond with the mortar. They also make interlocking watertight joints at points of overlap.
9-103. Install flashing at both the head and sill of window openings and at the intersection between a wall and roof. The flashing edges should turn upward as shown in Figure 9-42 to prevent drainage into the wall. Always install flashing in mortar joints. You can provide drainage for the wall above the flashing either by placing 1/4-inch cotton-rope drainage wicks at 18-inch spacings in the mortar joint just above the flashing or placing dowels in the proper mortar joint as you lay the brick and then remove them to make drainage holes. Where chimneys pass through the roof, the flashing should extend completely through the chimney wall and turn upwards 1 inch against the flue lining.
Figure 9-42. Installing flashing at window opening
9-104. Using the following steps to install flashing:
Step 1. Spread a 1/2-inch mortar bed on top of the brick, and then push the flashing sheet down firmly into the mortar. Spread a 1/2-inch mortar bed on the flashing, and then force the brick or sill onto the top of the flashing.
Step 2. Figure 9-42 above shows the proper flashing installations at both the head and the sill of a window. Note that the flashing fits under the face tier of brick at the steel lintel, then bends behind the face tier and over the top of the lintel.
Step 3. Figure 9-43 shows how to install flashing between the roof and the wall to prevent leakage at the intersection. Fit and caulk the upper end of the flashing into the groove of the raggle block as shown in Figure 9-43.
Figure 9-43. Flashing installation at intersection of roof and walls
FREEZE PROTECTION DURING CONSTRUCTION
9-105. Masonry walls built during cold weather may leak, because either the mortar froze before it set or the materials and walls were not adequately protected against freezing temperatures. During cold weather, prevent future wall leakage by:
9-106. Careless materials storage can cause time delays and/or contribute to poor workmanship, because you must remove all ice and snow and thaw masonry units before construction can proceed. Instead, completely cover all masonry units and mortar materials with tarpaulins or building paper. Store them on plank platforms either thick enough or raised high enough to prevent moisture absorption from the ground.
HEATING MORTAR INGREDIENTS
9-107. Heat both water and sand to a temperature not exceeding 160oF. Make sure that the temperature of the mortar--when you use it--is at least 70oF but not more than 120oF. Use steel mortar boxes on small jobs, and raise them about 1 foot above the ground so that you can supply heat to keep the mortar warm after mixing. Never add salt water to mortar to lower its freezing point.
CONSIDERING TEMPERATURE VARIATIONS
9-108. If the outside air temperature is below 40oF, the brick temperature when you lay it should be above 40oF on both sides of the masonry for at least 48 hours for Type M or S mortar, or for at least 72 hours for Type N mortar. If you use high-early-strength cement, reduce these time periods to 24 and 48 hours, respectively. Note that the use of high-early-strength cement in a mortar does not alter the setting rate much, but it does increase the rate of strength gain, thereby providing greater resistance to further freeze damage.
HEATING MASONRY UNITS
9-109. To prevent the warm mortar from cooling suddenly as it contacts the cold bricks, preheat all masonry units to about 40oF whenever the outside temperature is below 18oF. This requires careful planning and timing. When heat is required, provide inside brick storage so that you can supply heat at minimum expense.
9-110. In below-freezing weather, sprinkle any high-suction brick with warm water just before you lay it. Never lay masonry units on snow- or ice-covered mortar beds, because little or no bond will exist between the mortar and units when the base thaws. Keep the tops of unfinished walls carefully covered whenever work stops. If the covering comes off and ice or snow collects on the wall top, remove it with live steam before continuing.
PROTECTING COMPLETED WORK
9-111. How you protect masonry from freezing varies with weather conditions and the individual job. Job layout, desired rate of construction, and the prevailing weather conditions all determine the amount of protection and the type of heat necessary to maintain above-freezing temperatures within the wall until the mortar sets properly.
MATERIAL QUANTITIES REQUIRED
9-112. See Table 9-6 for the quantities of brick and mortar required for various masonry wall thickness.
Table 9-6. Quantities of materials required for brick walls
|David L. Heiserman, Editor||
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Revised: June 06, 2015