How to Prevent Rotting in a Wood Retaining Wall

retaining wall against hillside of boulders
What You'll Need
Green foundation-grade treated wood
Brown foundation-grade treated wood
Wood preservative
Paint brush

A wood retaining wall is a simple, attractive, and easy-to-build tool for converting steep slopes and awkward hills in your yard into usable, easily navigable land. Wood retaining walls can help you turn those slopes into attractive, terraced planting beds for flowers, herbs, or vegetables. The materials are fairly cheap and light. Sounds perfect, right? Well, almost; wood retaining walls aren’t without their flaws, the worst one being that they are prone to wood rot. The constant contact with wet soil and exposure to the elements puts the wood at risk. Keep in mind that the likelihood of rot will be highest in humid climates with a high precipitation rate, so if you live in such an area, you will definitely want to shell out a few more dollars to keep your wall protected than if you live in a mainly dry, sunny environment. The best way to prevent rotting in a wood retaining wall is to treat the wood prior to installation. Keep reading to find out more about how to prevent rotting in a wood retaining wall.

Step 1 - Order the Best Wood

The best way to reduce the chance of rot in a wood retaining wall is to start with the highest quality materials possible. Although builders often use “ground contact” rated wood for these types of walls, your best bet to have a truly protected wood retaining wall is to use foundation contact pressure-treated wood. This is wood that has been treated to withstand underground conditions, like the humidity from soil. On the downside, it is more expensive and typically harder to find than other grades of wood, so depending on your area you may have to do some hunting. Redwood and used rail ties are also good weather-resistant options.

Step 2 - Double Treat It

tools leaning against a wood retaining wall

Even though you’ve already got treated wood, you should double protect by treating it with wood preservative. This will form an even tougher barrier that will help keep the moisture out for a good long time. Wood preservative is available at any major hardware store. Apply it to the wood with a paintbrush according to manufacturer’s directions. You can also use creosote, which helps to keep the insects away, or weather sealer.

Step 3 - Form a Barrier

Another way to defend against rot is to try to form a protective barrier in between the treated wood and the soil. This can easily be accomplished by stapling a water-resistant tarp to the side of the wood wall that will be in contact with the soil. Another possibility is to build a mini retaining wall of stones or pebbles between the wood retaining wall and the earth.