Cost of Wood or Timber Retaining Walls
Average Cost Estimate
A wood or timber retaining wall is an effective means of controlling a sloped area in your yard to make use of the space while adding character to the landscape. Wood retaining walls are typically built with pressure-treated timber, and they’ll last 40 years or more, when treated or preserved properly.
This Costimate provides you with detailed wood retaining wall costs for materials and labor and DIY installation is an option too. Timber retaining wall prices from local and online sellers are given plus reader submissions of costs from their projects, all to assist you in budgeting for your wall.
Product and Supplies Cost Details
Wood/Timber Retaining Wall Cost Factors
How much your retaining wall will cost depends on the scope of the project. Length and height of the wall have the most impact due to the amount of needed retaining wall timbers. Specific costs are listed below.
Note: On this page, when we refer to a “square foot” of wall, we’re talking about the vertical face of the exposed and buried wall. For example, if you had a retaining wall 10 feet long and 3 feet high, that would be 30 square feet of vertical wall.
- Square Feet of Wall Face – Most walls are built with timbers approximately 6” high (they are 5.5” square) and 8’ long, so each timber is 4 square feet of wall face. As an example, a wall 60’ long and 4’ high will be 240 square feet of wall face. That number divided by 4 means you’ll need 60 timbers plus a few extra to replace damaged or warped material.
- Type of Timbers Used – Most timber retaining walls are built with either pressure treated 6″ x 6″ or used railroad ties. While the rail ties are treated differently for longer usage, new pressure treated timbers look better and tend to provide a more uniform appearance.
- Difficulty of Installation – If your retaining wall is on a hard to access slope, or the slope needs to have a lot of dirt removed to accommodate, it’s going to cost more.
- Steps or Corners – Basically, if your wall needs a set of stairs or has complicated corners, it’s going to cost a bit more than a standard retaining wall due to the added time to complete these features.
- Use of a Top Finish Board – Depending on your design or wall location you might want to add a 12”x2” cap on the wall for use as a bench, shelf for potted plants or simply to give the wall a finished look.
- Drainage Materials – Walls retaining significantly sloped areas will have large amounts of water run against them. Similar to a french drain system, placing stone beneath the first timber and a drain at the base of the slope-side of the wall will facilitate drainage of water that might otherwise cause faster deterioration of the wood – even pressure-treated wood, or complete failure of the wall itself when the water freezes and expands.
- Stain or Finish – Pressure treated wood can be stained once it has dried in 3-6 months, depending on your climate.
Cost of Supplies
Now let’s dig into actual wood retaining wall costs that will allow you to produce an estimate for your project.
- $8-$20 | Stakes or rebar and string to mark the path the wall will run and the height of its top.
- $40-$65 | 6’ level for checking that the ground is level and the wall going up straight.
- $24-$28 ea. | Pressure-treated timbers 8’ long and 6” square are the professional’s choice for building wood retaining walls.
- $22-$28 ea. | 2” x 12” pressure-treated 12’ boards for use as a cap, bench or shelf (optional).
- $2.75-$3.50 ea. | Pieces of ½” rebar 4’ long are driven into the ground through drilled pilot holes to anchor each base timber near both ends.
- 70-90 cents ea. | Galvanized 60d 12” spikes are driven through pilot holes every 8” to hold each layer of timber to the layer beneath it, so that’s 12 spikes per 8’ timber.
- $20-$27 per 5lb box |Decks screws every 8” are used to secure a cap to the top row of timber (optional).
- $20-$24 per cubic yard | A 2” layer of ¾” stone or similar material is installed and compacted beneath the first layer of timbers and then installed at outside foot of the wall to facilitate drainage – you’ll need about one cubic foot of drainage stone for every 3 linear feet of wall.
- $55-$70 ea. | 50’ roll of 4” perforated drain tile that lays on the stone at the outside base of the wall.
- $40-$50 ea. | 100’ roll of professional-grade landscape fabric is used over the drain tile to keep sediment from clogging it, and enough crushed stone is placed on top to hold it in place.
- $33-$45 per gallon | Exterior wood stain (optional)
- $6-$15 ea. | Brush for applying stain (optional)
Note: If you hire a landscape company to install your wood retaining wall it’s possible that the will have a wholesale account at a local lumber or home improvement store, so they might get better pricing on materials than you.
Permits, Inspection, and Installation Costs
Here are miscellaneous costs you might have, plus the timber retaining wall installation cost.
Permits and Inspection
Some building departments require a permit for any retaining wall while others only require one for a wall 4’ high and above. A quick call will let you know if you need one to comply with your local building codes.
Note on HOAs: If you are part of a homeowner’s association, make sure your fence complies with the HOA bylaws or risk having to modify or remove it.
- $0-$75 | Underground utility lines must be located and marked to prevent hitting them during digging. Call 811 to have this done. In most areas this is a free service provided by the utility companies. They don’t want the cost or liability of having to repair damaged lines.
- $35-$200 | Permit for the retaining wall if required for your project
- $200 – $350 – For retaining walls higher than 3 feet it’s strongly recommended (and may be required by local code) to hire an engineer for the design of the wall.
Installation Cost and Time
Building a wood retaining wall is a time-intensive project compared, for example, with building a wood fence. Here is the labor cost of installing a wood retaining wall.
- $4-$12 per square foot | Installation labor.
These are the factors that affect where your project will fall on the cost spectrum.
- Accessibility to Location—If your home is in a remote area, travel time for the crew will be longer and more fuel will be required, so cost will go up.
- Length of the fence – The base of the wall must be trenched, so for example, a wall 100’ long and 2’ high will cost more to install than a wall 50’ long but 4’ high, though both have 200 square feet of facing.
- Obstructions—Having to remove trees, roots, shrubs or large amounts of dirt in the path of the wall will raise costs.
- Soil Type—Hard or rocky soil takes more time to trench, so increases the cost.
- Time of Year – When landscape companies aren’t busy their estimates are more competitive. Having a retaining wall built in spring or summer will cost more than during fall or winter, in most regions of the country.
Note: In any season, the best strategy for getting the lowest estimates is to request bids from several companies and letting them know they are competing for the retaining wall job.
Completed Installation Time
Here’s how long it will take to install your retaining wall:
- 1-2 days | Simple installation of a wall less than 100 square feet
- 2-3 days | Simple installation up to 200 square feet or difficult installation of less than 100 square feet of retaining wall
- 4-6 days | Larger, more challenging installations
Day 1 Dig the trench for the base layer of timbers, install stone, lay the timbers and anchor them into the soil.
Day 2-4 are spent installing the remaining courses of timber and an optional cap.
Day 5+ might be required on large walls, especially high retaining walls that require additional supports.
In any job, the size of the crew will affect how fast the work goes. This time estimate is for a crew of two or three.
DIY or Hire a Pro
I’ve installed small, block retaining walls, as well as small border type retaining walls out of landscaping timbers. I’ve never put in a structural or timber retaining wall. That said, you’re going to need a lot of skill and a good bit of help to get the job if you choose to do it yourself.
- Requires a lot of digging and planning.
- Good with a wide array of hand tools, math, power tools.
- Able to lift heavy materials.
- Your going to need a few helpers and a good wheelbarrow driver.
If you’re a moderately experienced DIY’er, I don’t think you’ll have much trouble installing your own timber retaining wall. However, I still think it’s something left to the Pros.