Wood retaining walls are a classic choice and provide a sturdy option that can last as long as 40 years for pressure-treated wood and 20 for red cedar or redwood. It is an affordable option, but more limited in how creative you can get with your design.
How Long Do Pressure Treated Wood Retaining Walls Last? Untreated wood retaining walls (without a fence attached) are usually expected to last for around 20 years, but when they are built from high quality pressure treated wood, it's not unusual for them to last 30 years or more.
Concrete and Boulder Walls
Standing at the pinnacle of durability, poured concrete walls and boulder walls boast the longest lifespan. Their robustness ensures they can endure the test of time, often lasting 50 years and beyond.
It depends on the climate, the type of wood, its uses, and how well it's maintained. While pressure treated poles can stay up to 40 years without any signs of rot or decay, decks and flooring might only last around 10 years.
One way to protect wood is to use a wood preservative, which forms a tough barrier to for moisture and rot to break down over an extended period. You can apply wood preservative using a paint brush, use a solid insect repellant like creosote or weather sealer.
Your best bet will be one of three materials, redwood, pressure treated fir, and used rail ties.
Concrete is a common material for retaining walls because of its strength and durability. The typical lifespan of these walls is between 40 and 100 years, although they can persist for several decades.
A pressure treated fence post can generally last 10 to 25 years.
A pressure -treated post will last five to ten years in the ground without anything special done to it. For most construction purposes, the first line of defense against wood rotting is to keep it dry and away from soil contact.
Concrete blocks are a low-cost option for constructing a retaining wall. They are strong, long-lasting, and come in various sizes and forms to meet your design tastes.
Wooden walls are most prone to failure due to them rotting, being less durable than stone or concrete, and very often being improperly installed. 3 out of 4 times when we get a call about a wall tipping or having completely failed, it's wooden.
Wood and timber retaining walls are popular choices for DIY enthusiasts due to their affordability and ease of installation. Typically constructed using 6-by-6s, 6-by-8s, or 8-by-8s available at lumberyards and home centers, these walls are held together with screws, spikes, or rebar.
Generally, pressure-treated wood can last anywhere from 10 to 40 years, depending on a few factors.
Lay out the wall, excavate the soil behind it, and dig a trench 8 inches deep for the first course of timbers. Line the trench and excavation with landscape fabric, then add 2 or 3 inches of gravel and tamp it in place.
Apply a Protective Finish
To protect your wood from UV rays and moisture, apply a protective finish or sealant every few years. This will help prevent surface cracking, discoloration, and moisture absorption.
As a whole, the post and lumber specimens indicate an expected durability of over 50 years for creosote-treated wood and over 60 years for wood treated with pentachlorophenol, copper naphthenate, ACZA, or CCA.
All treated wood is now “ground contact”. “Ground contact” has a high chemical retention level and can be placed directly on or in the ground. This provides better protection against rot and decay.
Fill the first three inches up with gravel so the end of the post doesn't come into contact with the dirt. Gravel allows water to drain quickly away from the post and into the soil. Be sure to place the post in the center of the hole. Finally, fill the entire hole up with cement to the top.
Termites will eat pressure treated wood if the wood is old enough that it has lost some of its protection, if they can find an untreated edge, fi the wood stays damp enough for long enough and starts to rot, or if there is no other wood available.
#1 Grade: For projects where appearance is more important, #1 Grade has smaller and fewer knots and less wane compared to #2 Grade. It must meet a higher standard for aesthetics but may still come with some imperfections.
You can dry them out in a controlled manner to reduce risk of warping. Stack them up with air gaps on all sides. Rotate them routinely so the “top” doesn't dry out faster than the bottom. Monitor moisture content and once dry you can apply stain.
Wood Types - Different wood species have varying levels of natural resistance to decay. Common choices for retaining walls include cedar, redwood, and pressure-treated pine. Cedar and redwood naturally contain oils that resist decay and insects, making them popular choices for outdoor applications.
Long-lasting Strength
Concrete block walls are highly durable. They can last for decades without the need for repairs or replacements. The average design life of an SRW (segmental retaining wall) system is 75 years.
The best types of wood for a wood retaining wall are pressure-treated pine and fir, which are rated for ground contact.