How to Build a Cinder Block Wall
Cinder block walls or concrete masonry block walls have to to be constructed carefully and with the necessary reinforcement to account for a solid installation. Here are some simple steps to follow that will guide you through the process from layout until wall completion.
Cinder Block Wall Layout
Use a chalk or string to mark the layout of the proposed cinder block wall. Use a measuring tape or GPS equipment to ensure that your wall is long enough. After the wall is marked, place the cinder blocks as close as you can to the proposed wall to facilitate the installation. Remember not to add too much weight in certain areas that are not designed to withstand that temporary load. Wear required personal protective equipment and follow safety precautions.
Calculate the necessary cinder block by square feet. The typical cinder block is 8 by 16 inches meaning that a cinder block covers an area of 1.125 square feet. The total cinder blocks needed will be 1.125 times the area of the wall but be sure to subtract the openings such as windows, doors or any other architectural feature. The wall area is calculated by height times its length. Remember to add five percent to account for waste or any material that will be damaged. When completing the estimate make sure you have also included some material that will be needed as fillers that might be required when the height or wall to wall dimensions are not per plan.
Prepare the concrete footing where the cinder block wall will sit. Start the concrete footing by digging the area of the wall a few inches below the frost line, the maximum depth in the ground below which the soil does not freeze during the winter. Consult a structural engineer to design the footing including where to install the vertical reinforcement, which usually is placed every 24 inches. Normally a foundation wall with seven rows of block will be 24 inches wide and 12 inches deep and should have a footing 30 inches below grade. Remember to build a leveled footing where the cinder block will be placed.
The First Row
After placing the footing for the cinder block, start mixing your cement mortar in a wheelbarrow or with a trowel. Apply mortar to both sides of the poured concrete footings, starting at one of the wall’s corners. Place the cinder block on the mortar, level with the corner of the wall. Continue placing cinder blocks with mortar on one end, and fit it snugly to the previous blocks. Gently hit the cinder block with a hammer so it sits down into the mortar mix. Use a level to ensure that the cinder block wall is even. Repeat the process until the first row of cinder blocks is complete.
Finishing the First Row
Add mortar over the top of the cinder block line and install the spacers by gently pressing the spacers into the mortar on each side of the cinder block. If your footing has vertical reinforcement, this is the time to splice the next piece of vertical reinforcement. These spaces allow you to build a leveled wall and will be used as reference points to place your next line of cinder blocks. One trick subtract block wall is to build up the corners two or three blocks high, then stretch a string along the outside edge of each course as you work upward.
Finishing a Cinder Block Wall
Now it's time to finish our cinder block wall. Start laying the second, and subsequent courses, "butter" the sides of the first course with about an inch of mortar. Start the next row with half of a cinder block. Split a block by tapping a groove on each side with the claw. Doing this ensures that each block placed will be halfway between the previous cinder block rows. Repeat this process until you reach the desired height of your wall. Scrape off excess mortar from cinder block joints, horizontal and vertical, with a trowel. Once you are done, make sure you clean as fast as possible before the mortar is hardened otherwise you will need to spend some more time and money cleaning up the area.