Building a Wooden Retaining Wall

  1. mr-dirt-wooden-retaining-wall
  2. Once the grass matures, this will be one great-looking lawn!
  • The Problem

    The landscape was a little too steep for this homeowner to enjoy their backyard, so it was time to make a change by constructing a retaining wall and creating a more enjoyable and safer contour to the property surrounding the home. This retaining wall is relatively short, at less than 4 foot tall, but quite long and constructed of timber, for reasons that will quickly become apparent.

    Our Solution

    While a stone retaining wall is often preferred to using treated timber, wood retaining walls are far more economical than decorative stone that costs more than $5 per square foot for the material and require more labor to construct. The cost of stone is nominal when you are talking about adding landscaping touches to a small area, but large areas of coverage like this project can quickly get expensive. Timber also blends into a setting more naturally, and in this case, the wall would only be visible to the resident wildlife. This is a situation where wood is the perfect material, but proper construction techniques must be employed to get lasting results.

    When properly built, timber walls will last 20 years or more. The key to a lasting wooden retaining wall is understanding where water can collect and pool, speeding the decomposition of the wood. It is critical to give water a way to drain through and away from the retaining wall. Typically, a layer of waterproofing sheeting on the backside of the retaining wall will provide a barrier to moisture trapped in the fill. Also, crushed gravel packing underneath and along the length of the wall, along with perforated tubing to collect and move water allows trapped water to escape.

    Often, pressure treated Douglas fir is used for retaining walls, and for large projects such as this, recycled railroad ties can be a great alternative, providing longevity with low cost. Railroad ties are fine in shady areas, but when exposed to direct sunlight during the hottest weather, they can give off an odor from the creosote and wood preservatives used to treat the ties.

    For this project, we first cleared and contoured the area, then constructed the wall. Holes are drilled in the timbers and half-inch rebar is driven through the timbers to lock them into position with the ground and with the timbers as they are stacked. Vertical timbers are also used to reinforce the wall on the downhill slop so that pressure from the uphill side does not collapse the wall. Once the retaining wall is constructed, we haul in gravel for drainage and dirt to raise and contour the lawn, and finish off with seeding the new lawn and covering with straw to protect the seed.

    Building a retaining wall properly requires the right skill and knowledge. Mr. Dirt has the experience you need for a quality retaining wall. We ensure you get attractive and lasting results.


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