Building a Retaining Wall or Seawall

Big yards are a very desirable aspect of a home, but if they aren't flat and level, it may be difficult to get much use out of it. Pools, patios, and playgrounds all require level surfaces. A sloped yard can be made level through use of a retaining wall. Walls that protect a property line from erosion by a body of water also protect a yard and its safe use. Not only can walls increase the functionality of a yard space, it can also increase the aesthetic quality. Many precast wall materials are available at relatively low cost and can make the DIY retaining wall or seawall look like a professional work. Of course, before ever making major modifications to your property, always check the rules or laws of the homeowner's association or other authoritative body, and double check the exact location of your property line. Many wall-building project might have to be inspected and approved before they begin.

Building a Retaining Wall or Seawall

Why Build Walls?

Tools and Materials

The choice of material to build a retaining wall or seawall is as personal as the choice of landscaping or the color of the house. Obviously, found materials such as old railway ties or natural stone can make a beautiful wall. For most do-it-yourselfers, though, a trip to the local hardware store is probably going to produce simple concrete blocks or lumber. The design of the wall should be determined by its height: anything more than 3 feet should probably use wood with steel posts instead of stacked block. In any event, the wall will also need some porous landscaping fabric and leveling sand. The tools needed will include wood stakes, a carpenter's level, mason's line and a digging implement. Depending on the ground into which the wall will be built, this could be anything from a small shovel to a jackhammer. It is also recommended that safety equipment like glasses, gloves and back support be used at all times.

Procedure for Precast Blocks

The most basic seawall is simply cinder blocks, concrete slabs or large pieces of lumber tossed into the shallows to break up the incoming waves. This isn't exactly the most picturesque solution, however. A good seawall will be built high enough up the shore so as not to be submerged by high tide or high water. Retaining walls have a bit more leeway and should be built wherever they create the desired flat space. To begin, dig a trench for the foundation so that the soil will hold it in place. Use the stakes and mason's line to mark off the ends, the height, and other key points. Then start at the lowest point and dig to a depth equal to the size of the block and tamp down the earth. Lay the blocks in place and stack to the full height. It may be necessary to dig out further with each successive layer if the ground is extremely sloped. Use the carpenter's level to assess the top row of blocks and adjust as necessary. Line the cavity behind the wall with porous landscape fabric and refill.

Alternative Procedure

Precast blocks or stones aren't such a good idea for a seawall or a retaining wall more than a few feet tall. In these cases, the best bet is to go with steel posts spaced out 8 feet or so apart. To these posts should be attached metal brackets made of rebar or another strong, reinforced material, at various heights along the posts as determined by the size of the boards to be used; 2 by 12 inch should work nicely. Sink the posts about 2 feet into the ground to guarantee strength. Drill holes at the ends of each board that correspond to the spaced brackets on the posts. Attach the boards to the posts and brackets, and close them off with washers and nuts. Place gravel at the bottom of the interior cavity to help with drainage and then refill.

Joseph Nicholson

Joseph Nicholson is an independent analyst whose publishing achievements include a cover feature for "Futures Magazine" and a recurring column in the monthly newsletter of a private mint. He received a Bachelor of Arts in English from the University of Florida and is currently attending law school in San Francisco.