Knowing how to build a retaining wall can save hundreds of dollars during a yard renovation. Retaining walls not only help reduce erosion, but can also be used as a design element to delineate space. While large retaining walls should only be built by a licensed professional, a homeowner can build a small retaining wall without help.
Designing a Retaining Wall
Even a modest retaining wall requires some planning. Start by making a sketch of the wall on some graph paper. Graph paper will help to make an accurate drawing that will allow you to calculate the amount of blocks required to construct the wall. Draw not only a plan view, but also a section view that shows the part of the wall that will be underground. Dimension this drawing and use it as an informal blueprint to help you construct the wall.
After the drawing is complete, carefully evaluate the work involved with the project. A homeowner should not consider constructing a wall over four feet in height without the aid of a professional. Another good piece of DIY advice is to check with the local government for any code restrictions before building. A homeowner may need a building permit for even a modest retaining wall.
Once the scope of the project has been determined, visit the local Home Depot, Lowe's Home Improvement Store, or similar home improvement center for materials. Many companies manufacture retaining wall systems for homeowners. Read about prospective wall systems carefully, noting any particular height restrictions or building instructions.
How to Build a Retaining Wall Foundation
The foundation of a retaining wall determines the strength and longevity of the overall structure. For this reason, it is important to make sure that the foundation is adequate for the height of the wall.
In general, one inch of the retaining wall should be underground for every six to eight inches of wall height. For example, a wall that is three feet high should have a minimum of 4 ½ inches below ground level.
To build a retaining wall foundation, dig a trench of the required depth for the underground blocks, plus five inches. Make sure the trench has a consistent depth, and use a compactor to create a firm surface at the bottom of the trench.
Next, fill the trench with four inches of gravel. This will provide proper drainage for the wall. Compact this level as well, making sure it is as even as possible. On top of the gravel, add one inch of bedding sand. This will give the retaining wall blocks something to grab onto as they are laid.
Laying the Retaining Wall
Once the foundation has been created, begin laying the retaining wall blocks. Use a level to make sure that the blocks are even, and double check that the edges of the blocks touch to create a uniform surface.
When the first row is completed, backfill the row with crushed stone. This step will not only help further anchor the wall, but also prevent drainage problems. Compact the backfill as much as possible before laying another row.
Continue laying rows and adding backfill until the desired height is reached. The final row should consist of a retaining wall cap, which will help prevent erosion and water damage. A wall cap is simply a row of blocks with a solid top to prevent water from working its way into the backfill.
Even if you know how to build a retaining wall, consider hiring a professional for large projects. Many ardent do-it-yourselfers are quickly deterred by the amount of physical labor required to build a retaining wall. Although this project could be completed by a single person, it is strongly suggested that at least two people commit to working on a retaining wall to reduce fatigue.