The Simple Retaining Wall
Building your first retaining wall may seem a bit daunting. While challenging, if you start with a simple design, all you need is some basic Construction Equipment, lumber, and time to get the job done. Simple lumber-constructed retaining walls can be built in a couple of weekends: one to lay the trench for the foundation and the second for constructing the wall itself. Frequent construction tools required for this project include a circular saw, hardhats if desired,a variable speed drill, a good screwdriver set, a shovel, and carriage bolts. Supplies for the wall itself will include lumber, concrete mix, and gravel. Variable wood options can include standard wood, pressure-treated wood, or railroad ties.
Digging the Trench and Laying the Foundation
Depending in what your retaining wall will be used for, dig a trench to accommodate the height of the wall. If your wall is to hold back slope dirt, it could be as high as four (4) feet, maybe more. If building a wall for a raised garden bed, it may be as low as two (2) feet in height. The trench should be at least half again as deep of the height of the wall to keep the wall securely in place.
Once the trench is completed, dig individual holes for the posts which will be the same height from ground level to the top of the retaining wall, plus the depth of the hole in which it will stand. Depending on how long your wall will be, installing posts every three (3) to four (4) feet is recommended. Once the holes are dug, sink the posts into the hole. Mix and pour concrete to secure the post in place, leveling off the concrete smoothly. You will need to let this dry and cure for approximately one week, ensuring weather conditions are to remain dry.
Building the Retaining Wall
Depending on the type of wood you have purchased (pre-cut, railroad ties, or long boards), cut to desired length if required. Most simple retaining walls are constructed using either 2 X 6 or 2 X 12 length boards. Next, lay the boards so they will meet for bolting into the middle of the posts, then bolt securely in place with carriage bolts. Now, dig several 2 inch diameter tunnels beneath the wall to create a drainage system and fill with gravel. Once these are completed, backfill the space behind the wall with a minimum of 6 inches of gravel, topping off with surface soil. You are now ready to plant your garden or be confident the earth will be held in place, depending on which purpose the wall is for.