Essentials of
Masonry

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Part 2--Construct a Concrete-Block Wall

FIRST COURSE OF CONCRETE BLOCKS

Before mixing mortar and laying blocks, you should follow these steps:

  • Locate the corners of the wall.
  • Use a chalk line to mark the footing for aligning the first course of blocks.
  • Check the wall layout by placing the blocks along the wall without mortar. Remember to leave a 3/8-inch gap between each block for the mortar joint (Figure 2-5). This will tell you if any cutting is necessary.

Figure 2-5.  Laying out blocks without mortar
Figure 2-5. Laying out blocks without mortar

2-9. Spreading the Mortar Bed. Spread a full bed of mortar, and furrow it with a trowel. This will ensure that plenty of mortar is on the bottom of the blocks for the first course (Figure 2-6).

Figure 2-6.  Spreading and furrowing the mortar bed
Figure 2-6. Spreading and furrowing the mortar bed

Lay the corner block first and carefully position it. Be sure to lay all blocks with the thicker side of the face shell up to provide a larger mortar bedding area (Figure 2-7).

Figure 2-7.  Positioning the corner block
Figure 2-7. Positioning the corner block

2-10. Making Vertical Joints. Apply mortar to the ends of the blocks for vertical joints. You can save time by placing several blocks on the ends and applying mortar to the vertical faces in one operation (Figure 2-8). Then place each block over its final position and push downward into the mortar bed and against the previously laid block to obtain a well-filled vertical joint (Figure 2-9).

Figure 2-8.  Applying mortar for vertical joints
Figure 2-8. Applying mortar for vertical joints

Figure 2-9.  Positioning the block
Figure 2-9. Positioning the block

2-11. Aligning, Leveling, and Plumbing. Lay the first course of blocks with great care to ensure that they are properly aligned, leveled, and plumbed. This will make the next course of blocks and the wall itself straight and true. After you have laid three or four blocks, use the mason's level as a straightedge to ensure correct alignment of the blocks. Check the first course of blocks carefully with the level, bringing them to the proper grade. Plumb the blocks by tapping them with the trowel handle (Figure 2-10).

Figure 2-10.  Leveling and plumbing the blocks
Figure 2-10. Leveling and plumbing the blocks

 

 

David L. Heiserman, Editor

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Revised: June 06, 2015