The first course of block is laid on top of a __________ placed on top of the footing.

• A. Gravel base
• B. Bed of mortar
• C. Sand bed
• D. Concrete slab

Answer: (B)

Starting a masonry wall requires a level, bonded surface to anchor the first block. A bed of mortar laid on top of the footing provides that surface. It levels out small irregularities in the footing and bonds the first course to the foundation so the wall stays plumb as you build upward. Without mortar, a gravel base would shift, and a sand bed wouldn’t hold its shape or bond the blocks. A concrete slab isn’t used as the immediate surface for the first course in this setup, because the blocks need the adhesive grip of mortar on the footing. So the mortar bed best meets both the leveling and bonding needs for the first course.