Uncle Bobs Tips

How to Build a Retaining Wall

How to Build a Retaining Wall

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I remember as a little kid rolling down my sloping front yard. It never occurred to me then to wonder why the slope didn't continue to the back of the house. I know now. It was the natural stone retaining walls that my dad had built to keep things level. Retaining walls are the easiest way to take an unusable piece of mountain landscape and turn it into flattop in no time..well..flat.

Andrew Lein made me laugh when he wrote, "Any moron can build a retaining wall, and many have. Look around your neighborhood" Funny, yes, but sad as well. Sad because it's true. Funny because it's not you. Retaining walls can be as simple as a decorative structure for holding your prized petunias or as significant as the supporting wall of a house or landscape built on a slope. It's important to take into consideration what this wall will be supporting. A large vehicle or building will require a stronger retaining wall (perhaps poured concrete), while a landscape or decorative wall can easily be done with pre-fab stones. Either way, you should get ready to roll up your sleeves and get down in the dirt.

While numerous materials are available and will certainly vary depending on the degree of abuse this one is going to take, natural stone retaining walls are easy to build and appealing additions to your landscape. Ready-made concrete slabs are an easy solution, and work much better when being used for unusual shapes or curved edges. Pre-cast stones, however, can't be used for tall projects (not recommended for anything taller than 3'), and they don't look as realistic as natural stone. Retaining walls meant for the long haul can be made from concrete or metal rods. Wood and pre-cast are better suited for smaller projects.

Two words of caution before you even start. Check out the building codes in your area because you may need to acquire a permit before doing any sort of construction. The second is a recommendation to ask your utility companies where their lines are on your property. This ensures that there are no explosions, floods, or other unexpected surprises along the way.

When building a retaining wall, you want the first layer of stones or the first few feet of other materials to be in the ground. For this reason, once you've marked off the position of your wall (use some string and wood pegs or the like), you're going to dig into the ground a trench that is just a little wider than your building material and several feet deep. Smooth out the bottom and lay down a layer of coarse material (like sand), keeping things as level as possible.

When you put in your first stone, make sure it is level on each side and flush against the front wall evenly (the back wall will be filled in with dirt later on). Adjust accordingly, and repeat for each additional stone. Once the foundation layer is in place, check that everything is level and packed down tightly.

Your second level and on will be the same with the exception of one thing. At the beginning of each new level, a half a stone should be placed to create the offset look (if this is your design). You can use a string to guide your stone placements if you so choose.

Fill in the trench with the dug up soil and pack it in solidly. Cover up the trench with topsoil, flowers, or planters. Many recommend putting a sheet of landscaping fabric behind the wall and up the hill for a few feet to keep soil off the wall. Fill in and enjoy the flat surface. That's Man 1, Nature 0.

Additional info:

Pour concrete, perforated tubing and gravel are also materials commonly used when building a solid retaining wall. Gravel is especially helpful for combating frost damage (from expansion).

Fine tune each piece of your building material with a chisel or large hammer then check with a level. This may take several tries but be particular if you want a nice even wall.

Pre-cast blocks come with a groove or lip to allow for mortar-less construction, which is why people don't use them for taller projects. For larger plans blocks can be used to make several smaller walls, building height gradually. This also creates a dramatic effect.

Remember the foundation wall is the key to a strong and successful retaining wall. A strong and solid foundation will give you a long lasting and secure retaining wall.

Creating a leaning back effect on your retaining wall will offset the center of gravity. This makes it harder for the wall to be pushed down, thus making it a more reliable and durable wall.

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