DIY Network

Retaining Wall Retaining Wall From "Grounds for Improvement" episode DGFI-111

It’s time to install the retaining wall. For that, we’re using composite timbers, which are ideal for projects involving ground contact because they won’t decompose.

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	Figure A
	Figure B

The composite timbers are made from recycled materials, such as plastic bags. Starting with the base course construction, make sure you check for level once the timbers have been placed. This is the most important step since the remaining wall will be built on top of the base course.

Use a mallet to hammer the timbers into place. To secure them, drill three holes: one on each side and one in the middle. Then run rebar through the holes, into the ground.

To create a decorative finished edge, use a speed square to mark an angle on one of the timbers. Then use a circular saw to cut the timber (figure A). You’ll want to make sure it has a carbide blade when you’re cutting composite timbers. Make sure to wear gloves and safety goggles when using the circular saw. Other options for cutting composite timber are compound miter saws and chainsaws.

After this piece of timber has been cut, place it on top of the timber that’s already been installed into the ground (figure B). You’ll need to secure this layer of timber with three spikes spaced evenly and hammer them in with a sledgehammer. It’s easier to hammer them when the spike is angled towards you and you keep a steady rhythm.

After the first set of timbers have been placed, continue along with the other layers, using the same process: place down the composite timber, level it, drill the holes, and hammer it into place. You’ll want to secure the lower course with rebar and timber spikes with a finished head for all the top courses where a fastener head can be seen.

In order to make sure the edges of your new retaining wall do not hang over the front park, lay the pieces beforehand and measure out how far they hang over. After you’ve marked where the extra bit hangs over, you can go back and cut it with the circular saw. You’ll be able to have a more precise fit every time! The edges of your retaining wall are secured the same way, using rebar for the lower course and timber spikes for the top course.