How to Build a Cinder Block Fence
Make a professional-looking cinder block fence to protect your privacy and as a barrier to the world. Block noise pollution, protect your privacy, and keep your yard free of unwanted pests with a cinder block fence.
Estimate your expenses. Calculate the number of cinder blocks that you will need by establishing the length and height of the wall. Allow 1/4 inch between cinder blocks (where the gap is filled with concrete) to get the number of blocks required. Remember that each cinder block is typically 7.63 inches by 7.63 inches by 15.63 inches. Estimate the amount of cement you will need based on the area of the footing and the number of cinder blocks by using an online concrete calculator for your specific fence (see resources).
Dig the foundation for your cinder block fence. Make sure that the foundation goes deeper than the frost line. In most locations, this means that you need to dig 3 feet deep and 2 feet wide. Compact the soil that the wall will rest upon. Pour a concrete footing that is 4 inches deep.
Use a straight board on edge and place a level across it to see if the concrete is level at various angles. Scrape the concrete with another board to make it level. Wait for the concrete to cure.
Drive steel fence posts into the ground, and tie a string between them at the height of one cinder block above the ground. Use this string as a guide to keep the wall straight.
Throw cement down 3 feet at a time with a trowel, and smooth it down to about 3 inches. Place a cinder block along the ground over this cement, running parallel to the foundation. Every five feet, lay a cinder block perpendicular to the other cinder blocks with the block centered in line with the rest of the wall.
Use the handle of your trowel to tap the cinder block level. Check the blocks with your level, and then correct the block position as needed to bring it level.
Use the trowel to put cement on the side of the block where the next block will press up against it. Place the next block into the cement on the foundation and up against the next block, where the cement will hold the two bricks together. Repeat the process to make a layer of bricks all the way around the foundation, 3 feet at a time. Allow the first layer to cure.
Lay the next layer on top of the first, staggering the joints so that the seams between the blocks do not line up. At the ends of the wall and over the perpendicular joints, lay partial bricks to prevent the seams from lining up.
Over the perpendicular blocks, use quarter blocks at the ends as a brick goes through the center of the perpendicular block. Make sure that the cement is on top of the first layer and between the bricks. Again, work 3 feet at a time so that the concrete does not firm up too much. Wait for the second layer to cure. Repeat the process until the wall is 5 to 6 feet above the ground.
At the top of the wall, cram wads of newspaper into the top hole of the cinder blocks 6 inches down. Throw 1/2 pound of concrete on the top of the newsprint. After the concrete cures, throw a little more concrete on top to seal any remaining gaps inside the cinder block. Allow the concrete to cure and then fill up the rest of the block to the top.
- Apply sealant and paint the wall to prevent water from infiltrating the wall down to the foundation. Add a polyurea coating for extra strength (see video in resources section).
- If water gets into the wall, freeze/thaw cycles will heave the wall and make it unstable. Also, make sure that the wall foundation is not near tree roots or anything that will undermine the foundation. Make sure that the wall is stable by cautiously testing it.
- Cinder blocks and concrete (see step 1 for quantity estimation)
- Sledge hammer (to compact the dirt)
- Steel fence posts (one per corner)
- Nylon string the length of the fence perimeter (thick enough to be readily visible at a distance)
- Straight 2-by-4 board (8 feet long)
- Sealant (for waterproofing)
- Paint or polyurea coating