How to Lay a Concrete Block Foundation Using Rebars

Cut rebar to a length a few inches higher than the planned wall. The bar will need to stick out of the tops of the blocks by 4 or 5 inches. There will be plenty of overlapping hole space in your rows of blocks. It is usually easier to stack and mortar your blocks, then place the rebar in cement afterward.

Place cinder blocks on the concrete footings. These are normally pre-poured. These are typically placed about 1 foot underground, and form the perimeter of the foundation. Never place blocks directly on soil or gravel for a residential foundation. The block wall, in other words, will rest upon these concrete footings.

Place your first row of mortar about 1 inch thick on the concrete footings. This is where your first row of blocks will be placed. Always wait about 45 minutes before placing your blocks. Do not put blocks on fresh mortar, wait until it begins to congeal. It is typical for masons to spread enough mortar for about 6 blocks at a time.

Lay your cinder blocks always facing upward. The best way to install your rebar is to just jam them in from the top of the wall to the bottom. Use rebar that is no thinner than 1/2 inch; most projects use a 5/8 inch bar. It is always wise to place rebar in each cell of the block at the corners of the foundation. Since corners are more vulnerable to breaking and cracking during cement curing, these need extra protection.

Pour 1 foot of concrete where you will place the bar. Normally, you will space the bars about 4 feet apart. Wait about a half hour. When the concrete begins to dry a bit, then roughly jam the bar into the concrete. Push as far as you can go, using a mallet if necessary. The concrete will easily receive the bar and permit it to stick up.

Pour the concrete into every cell of the blocks, covering the bars to the top of the last row. Use the trowel to whisk away any excess mortar from the sides and the top. The rebar, still sticking up, will help connect the foundation to the home.