How to Lay a Cement Block Foundation

Pour a footing for the cement block foundation that is beneath the frost line, or set it directly on bedrock. Be sure that the surface of the footing is perfectly level to create a solid base for the cement block wall.

Using a trowel, spread a 1/2-inch-thick layer of mortar on the upper surface of the footing.

Spread mortar over one end of a concrete block, and then set the block into the bed of mortar on the footing. Seat the block into the mortar by tapping on the block firmly with the handle of the trowel.

Spread mortar over one face of another concrete block, and set it against the first one, with the mortared side facing away from the first block. Seat the second block by tapping it firmly with the handle of the trowel and pushing it down into the bed of mortar and back into the other block.

Complete the first course of blocks by adding blocks for the length of the wall, being sure to include adequate mortar between all of the blocks.

Spread a 1/2-inch-thick bed of mortar over the top surface of the first course of blocks.

Place a block on top of the first course of blocks to begin the second course. Place this block so that its center is directly above a joint between two blocks beneath it. This will create a zig-zag pattern of vertical joints that will help to strengthen the wall and hold it together.

Check the level of the wall with a 4-foot level after every course. The side of the wall should be perfectly vertical, and the top faces of the blocks should be perfectly level.

Continue laying courses of blocks on the wall until the foundation has reached the required height.