Essentials of
Masonry

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Part 2--Construct a Concrete-Block Wall

LAYING CONCRETE BLOCKS BETWEEN CORNERS

To ensure a good bond, do not spread mortar too far ahead of the actual laying of the block. When mortar is allowed to sit, it will stiffen and lose its plasticity. As each block is laid, cut off excess mortar with your trowel and work it back into the fresh mortar (Figure 2-16).

 Figure 2-16.  Cutting off excess mortar
Figure 2-16. Cutting off excess mortar

2-18. Using a Mason's Line. As you fill in the wall between the corners, stretch a mason's line from corner to corner for each course. Lay the top outside edge of each block to his line. Tip the block slightly toward you so you can see the edge of the course below, making sure that the lower edge of the block is directly over the course below (Figure 2-17).

 Figure 2-17.  Laying the top outside edge of the block to the line
Figure 2-17. Laying the top outside edge of the block to the line

2-19. Making Adjustments. You must make all adjustments to the final position of the block while the mortar is flexible. If you try to make adjustments after the mortar has stiffened, it will break the mortar bond and allow water to penetrate. Level and align each block to the mason's line by tapping it lightly with the trowel handle.

2-20. Installing the Closure Block. The last block to be installed in every course is called the closure block. When you install the closure block butter all edges of the opening in the wall and all four vertical edges of the closure block with mortar. Carefully lower the block into place. If any mortar falls out and leaves an opening in the joint, remove the block and repeat the procedures (Figure 2-18).

Figure 2-18.  Installing the closure block
Figure 2-18. Installing the closure block

TOOLING THE JOINTS

Proper tooling of mortar joints helps produce a weathertight, neat, and durable concrete-block wall. For exterior concrete, the mortar joints you make should be concave or V-joints (Figure 2-19). Tool the vertical jointer first, followed by the horizontal joints with a longer jointer.

Figure 2-19.  Mortar joints
Figure 2-19. Mortar joints

2-21. Jointers. To finish mortar joints, you will use a jointer, also called a finishing tool (Figure 2-20).

Figure 2-20.  Jointers
Figure 2-20. Jointers

a. Sled Runner. Use a sled-runner jointer to tool horizontal joint (Figure 2-21).

Figure 2-21.  Tooling horizontal joints
Figure 2-21. Tooling horizontal joints

b. S-shaped. Use the S-shaped jointer to tool vertical joints (Figure 2-22). This is called striking.

Figure 2-22.   Striking vertical joints
Figure 2-22. Striking vertical joints

2-22. Burrs. You can reduce burring by finishing the horizontal mortar joints before you finish the vertical joints. If mortar burrs remain on the wall after you have finished tooling, you should remove them. This will prevent small amounts of water from being lodged in the mortar joint.

 

David L. Heiserman, Editor

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Revised: June 06, 2015