Pressure Treated Wood Retaining Wall Design

A wood retaining wall is easy to install, and typically lower cost than other retaining wall solutions. They’re perfect for short slopes that still have some erosion risk, and allow you to raise garden beds for good looks and convenience.

This is one reason that most modern wood retaining wall designs use pressure-treated timbers instead of older alternatives (like railway sleepers). While older and ‘recycled’ wood can be problematic, modern timbers are created specifically for environmental saftey.

You can also look to cedar or redwood, which preserve well naturally, as alternatives for timber walls. Especially if you’re including an edible garden in the landscape!

Timber retaining walls are typically only suitable where you need a wall under four foot in height. Often holes are drilled through heavy wood, with steel rods inserted down to the grade. Sometimes a ‘deadman’, or a rebar extension back into the slope, is added for additional reinforcement.

Pressure treated timber does best with minimal cuts and holes introduced to the boards. Any point where you drill into or use nails on the pressure-treated board will introduce a weak spot in that protection.

This means they’re great for straight or square landscape features, rather than used for circular, wavy, or tight designs where a block retaining wall might be a better choice.

They create a soft and natural focal point in your garden, and blend perfectly with deck areas or anywhere else you want a simple, natural, but effective retaining wall to enjoy.

When you add a retaining wall to the landscape, you are adding a structure that will change how the water flows over the soil. Often, this is for the better, creating a landscape that drains well and keeps the foundation soil steady and supportive.

Only if the engineering is on point and you used the right materials and wall height, however. Wet soil and gardening materials create an altogether different set of forces, as well as additional weight, on the retaining walls.

Retaining walls using block systems are often used where the space is tight or limited, or where access is difficult. These are often the points at which you see water gather, too, so expert drainage design is a must.

If properly created, set up with great drainage, and well preserved, a wood retaining wall can last 2 decades and more.

Of course, eventually the wood itself will be the weak point. No matter how well designed, or what posts or rebar you use, the one end of the timber will be in contact with the earth, and thus moisture.

It’s this combination of rot and the weight of the dirt being contained by the timbers that eventually leads to failure in the timber of a wood retaining wall.

While they have a naturally shorter lifespan than other retaining walls, they can still be a long-lasting and beautiful addition to a landscape. Just like a deck or other landscape feature, they won’t last forever- but a well cared-for lumber retaining wall will last long enough.

Obviously, no matter what you do, wood timbers simply don’t have the longevity of other retaining wall types. However, by using pressure-treated wood boards, you’ve already taken a massive step towards a long-lasting, cost-effective option that you can rely on.

One of the best possible ways to ensure your retaining wall posts don’t rot in the ground is ensuring optimal water removal around the retaining wall. Paired with a trusted wood preservative and smart use of landscape fabric to cut down on cracking and soil/root pressure, this alone can greatly extend the lifespan of your timber retaining wall.

So does using the right construction method. That’s where the expertise of the Xpress Engineering team will come into play. We’ll advise on what’s needed to get the best from your wood walls, from drainage requirements to possibly reinforcing the wall with rebar.

Most of the timbers will also lay at rest slightly above the bulk of the dirt, ensuring minimum contact with moisture.

Our expert team will make sure your wall is a project with maximum longevity, considering the incline, ground pressure, and lumber so you get the results you’re wanting.

Backfill and drainage are critical in any retaining wall design, but especially so for a timber retaining wall. If you ensure water does not pool in the soil or at the post level of the retaining wall, you help ensure a longer lifespan for the lumber you use.

Gravel is often used both at the footing and edge of the retaining wall, as well as in a layer of the backfill, to reduce moisture exposure.

Backfill simply refers to the earth and other substrate that is filled back behind the retaining wall once it is completed. As you make a retaining wall, it’s common to dig the area out completely. They will then fill the hole back with suitable backfill.

The top layer will be usable dirt perfect for your plantings or overall design, but that creates a very heavy force pushing on the retaining wall, and does not always create good drainage, either.

Instead, when your Xpress Engineering experts are installing the length of your retaining walls, they will build drainage solutions, from gravel beds to custom drainage, into the design.

This helps keep the wall steady, reduce the force acting on the lumber, minimize the weaknesses left by nails and drill holes, and help extend the lifespan of a timber retaining wall.

Are you picturing a cascading timber row leading down to your veggie garden or entertainment area? Let the Xpress Engineering team help make those dreams a reality today.