How to pour a concrete retaining wall

How to pour a concrete retaining wall

A concrete retaining wall can be a great way to landscape your yard if you have ground on different levels. Many people also do retaining walls with recycled materials to keep the cost down.

For some concrete retaining wall ideas you should search the internet. If you’re looking for how to do a basic poured wall, here is a guide for you following.

Concrete retaining wall design

To begin with, we need to determine the frost line in your local area by inquiring with the local building authorities. This line is the boundary below which the ground does not typically freeze during winter months and it can vary greatly from place to place.

Use your shovel to dig a trench about 12 inches deep (or deeper if your local frost line requires it) as wide as you would like your retaining wall to be. Also, as we’re building forms it should be wide enough to work comfortably where we need to.

I usually dig some extra away so that I can have little room to play with the forms for concrete. The height could need adjustment or something else. It also helps to keep the other soil from falling straight to the working space. Work is heavy, but the benefits are many. If the work is done with a machine like an excavator, I see no reason not to.

How to build concrete forms for retaining wall

Step 1: Cut your plywood sheets into 8-foot panels that measure 3 1/2 inches taller than the projected above-ground height of your retaining wall. For measuring using your tape measure, a straight edge and circular saw will be enough. Cut enough panels to fit both sides along the full length of your retaining wall. These panels will make up the wall frame.

Step 2: Cut 2×4 studs to the height of your plywood wall frame using a circular or hand saw. Then we can fasten the studs into the plywood by nails or screws. I personally like screws for easy disassembly, but anything will do.

Start at one end of each plywood panel and install one stud every 24 inches or so. The studs should be screwed or nailed into the plywood at a couple of points so they will be sturdy in place.

Step 3: After the plywood, frames are set up, you can carry them over to the trench and place them so that the studs are vertical pointing outside both sides of the trench. Use your level to check that all is straight and adjust as needed.

Step 4: Measure the gaps between your two plywood frame pieces at each end. Cut plywood to fit the gaps and fasten them in place with screws or nails. Depending on the size of the form and concrete that needs to be poured, it might be good to reinforce the ends so no accidental giving away of plywood will happen.

Step 5: Use your paintbrush to coat the inner walls of your plywood frame with concrete form oil to ease removal after the concrete has dried. Small forms can do without if the forms are removed the next day, but with a bigger pour, it might be a good idea to oil them.

Step 6: After oiling has been taken care of, cut 2×4 inch studs into spacers to fit the width of the interior of your plywood frame. Measure the gap between your plywood boards and use your circular saw to cut the studs. Place the studs between your plywood sheets and use your nails or screws again to fit them in place.

Remember to mount the spacers above the wall itself, in the 3 1/2 inches of extra space, you factored into the height of the frame. You don’t want to have them inside the wall when you pour the concrete as they will only decay there. These spacers will maintain a uniform wall width from top to bottom.

Place support system for concrete forms

The last stop of our concrete form building should be a buttress support system. It will be a counterforce for the concrete mass so our form won’t give in with the pressure. This way our end result will be of equal thickness everywhere.

Start by measuring the length of your plywood wall frame from end to end. Cut and fit 2×4 inch studs to fit this length and lay them along the bottom edge of the plywood frame where it touches the ground to create a support rail.

Cut some more 2×4 inch studs to a length of 4 feet each. Place these studs against the support rail (one every 24 inches or so) in the form of a buttress. Cut some more studs into short stakes.

Drive the pointed stakes into the ground with your hammer so that it wedges your buttress in place and provides further support for the plywood frame. Repeat this process along both sides of the plywood frame.

Concrete wall rebar stack

Place the concrete wall rebar

Concrete is weak to pulling forces even when it can handle lots of weight. Installing rebar will help to fight that and the concrete retaining wall can actually handle the ground pressure.

To begin with, hammer rods of rebar into the trench right down the center of the plywood frame to a depth of about 12 inches. Place one bar every 18 inches or so.

Tie the bars to the top frame spacers with number 8 or 9 tie wire. The idea is to keep them straight and centered. Cross your vertical rebar with horizontal lengths placed every 18 inches or so from bottom to top. Tie them in place with your tie wire.

Mix and pour your concrete according to the manufacturer’s guidelines. It would be good to have a concrete vibrator to let the air escape from the poured concrete. If you don’t have one at hand, bang the sides of the form with a hammer to let some of the air bubbles escape. After we have poured the concrete, we can finish the top with a float.

Now it’s time to wait that the concrete will cure. The info is usually in the bag of ready mix. Remember that weather will also affect curing time. Cold weather usually makes it last longer. When you remove the forms and inspect the wall in cold weather if it still feels soft don’t worry too much. It will harden with time.

Conclusion

Poured concrete retaining wall is a sturdy way to build one. If you add rebar it can hold against the pressure of ground quite well without giving in.

If you dislike the look of poured concrete, think about different ways to build the forms. Using plywood or wooden board will give different looking results. Or maybe you can stucco it.

Somewhere like garden a lively surface could be appreciated while next to modern house a level surface could look better. In the end, it’s a matter of taste.

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