A strong foundation is key to any structure that’s built to last, and walls are no exception. If you’re building a wall with cinder blocks, it’s important to make sure the footing will support the weight of the wall before you pour concrete into your footings. Follow these steps and you’ll be on your way to having a sturdy wall:
Calculate how much concrete you need.
In order to properly prepare for your footing, you’ll first need to calculate how much concrete you will need.
- Calculate the area of your wall. The best way to do this is by measuring and marking off the dimensions with a tape measure and then using a calculator or a tape measure app on your phone to find the square footage.
- Calculate how deep each footing should be based on soil type and local building codes. Check your area’s building code information or talk with an experienced builder if you aren’t sure what depth you should use for your area’s soil type (this will usually be between 6″ – 10″). If possible, use frost protection in cold climates that have shallow frost depths (less than 12″), but don’t let this be an excuse not to build a cinder block wall.
- Calculate how much concrete is needed per footing: Multiply together the area of each footer * its depth from above; then divide by 2700 cubic inches per yard of concrete (for example: 8’x4’x6″ = 192 sqft x 3″, 192/2700 = .085 yards). This gives us our total cubic inches of concrete needed per footer; add 5% more than this number as waste due to overfill during pouring (e.g., if we calculated that we needed 24 cubic feet total across all three footers, add 1 extra cubic foot so we’d end up purchasing 25). Now get in contact with a concrete supplier!
Dig the footings.
Dig the footings.
- Use a shovel to dig the trenches 9 inches wide and 12 inches deep. (If you’re making a small wall, you might be able to get away with digging 5-inch trenches.)
- Measure out the width and depth of your trench using a tape measure.
- Put down some marking string so that you know where to make contact with your trowel later on. You’ll want it at least 3 inches above ground level or else water could collect in your top course of blocks and lead them to rot faster than usual. If you have access to lasers, use those instead—they’re much easier!
- If necessary, use stakes or something similar in each corner of your trench so that when it’s filled with concrete, there will be no chance whatsoever that things will shift around when we come back tomorrow morning ready for phase two: laying block.
Lay out your footings.
Once you have your plan and materials ready, you can begin to lay out the footings.
If you are building a wall with cinder blocks, make sure that each footing is level and deep enough to support the weight of the wall. The bottom of each footing should be at least 1 ½ inches below ground level, but it should never extend more than 2 feet below grade. Also, make sure there is an adequate amount of space between your footings; generally speaking, this should be about 3 inches for every 2 feet in height for walls less than 12 feet tall. This will help prevent cracks from forming in your foundation due to soil pressure once it settles over time after construction is completed.
The width of each footing depends on how far apart they need to be placed: wider footings provide greater stability against earthquakes while narrow ones allow for easier placement but may not hold up as well under heavy loads (e.g., vehicles).
Mark and cut the rebar to fit inside the footing trenches.
- Mark the rebar on one end and cut it to size.
- Place the rebar in the trench so that its ends are flush with the bottom and side of the trench, then tap it level with a hammer until it’s perfectly straight.
Use enough rebar to fill up your footing trenches by at least 1/2 inch overhang on each side, or as much as you can so that there’s not any space for soil between them if possible.
Add the rebar to the trenches, then fill them with concrete.
Once the concrete is dry, use a shovel and trowel to smooth it out, troweling away from your footing so that you don’t disturb any rebar.
You will also need to add water to your mixer if you are mixing on site. Add water first, then add the rest of the ingredients in order (concrete mix, gravel). For best results and safety, wear protective clothing such as work gloves and eye protection.
Let the concrete set up before continuing with the cinder block wall.
You will need to let the concrete cure for a few days so that it can harden completely. It is recommended that you wait at least 24 hours, though 48 hours and up are even better if possible. If you are in a hurry, then it would be best to wait 72 hours before continuing with your cinder block wall.
If you have chosen to make a footing using cinder blocks instead of concrete blocks or other materials, then this step is unnecessary.
Building a wall that is sturdy enough to last takes more than just putting blocks in place and stacking them high.
Building a wall that is sturdy enough to last takes more than just putting blocks in place and stacking them high. The footing must be deep enough, wide enough, and level enough to support the weight of the wall you’re building with it. Footings are made of specially formulated concrete—with reinforcing bar or rebar—and should be poured carefully so as not to crack or settle unevenly over time.
To lay out where your footing should go: Use treated wooden stakes (or metal ones if you prefer) to mark where each end of your footer will be located, then dig into the ground until you reach solid soil and bedrock below it.
Hopefully, we’ve given you the tools to get started on your cinder block wall. As you can see, it’s not a difficult project, but it does require some heavy lifting and careful attention to detail. Once you get the footing in place and make sure everything is level, you can start laying down your blocks.