Landscape Timbers

What a landscape timber actually is

Most of what gets sold as a "landscape timber" at a big-box store is a 3" x 5" peeler core with rounded edges, about eight feet long. It works for a low border and not much else.

Wasatch Timber sells the other kind: rough-sawn, true-dimensional timber in real sizes, from 4x4 up to 16x16, in lengths to 24 feet and beyond. A 6x6 from us measures a full six inches by six inches - not 5-1/2". That matters when you're stacking courses, cutting joinery, or matching an existing wall.

Choosing a size

Size is driven by the load the timber carries and how the wall is built, not by looks alone.

• 4x4 - bed borders, edging, low garden walls of one or two courses, tree wells. One person can carry an 8-footer.
• 6x6 - raised beds, terraced steps, low retaining walls, parking curbs. The workhorse size, and the best balance of mass, cost, and handling.
• 8x8 - taller retaining walls, stair stringers and treads, heavy borders. A two-person lift, and it reads as substantial from the street.
• 10x10 and up - feature walls, seat walls, monumental steps, entry columns. Equipment recommended for placement. Available to 16x16.

Rough-sawn timber is full dimension. Surfaced (S4S) timber runs roughly 1/2" under the nominal size - an S4S 6x6 measures about 5-1/2" square. Decide which you want before laying out courses, because that difference compounds over a four-course wall.

Material options

There's no single right species. The choice trades off how long the wood lasts against soil, how it looks, and what it costs.

Douglas Fir #1 FOHC Timber
Premium #1 grade, free of heart center, rough sawn, true dimensional. Strong, straight, and stable - the standard for landscape work where the timber carries real load. Douglas Fir isn't naturally rot resistant, so anything touching soil should be sealed or treated.

S4S Douglas Fir Timber
The same Douglas Fir, surfaced on all four sides. Choose it for clean, smooth faces - seat walls, steps, anything near a patio. Remember the 1/2"-under sizing.

Inland Cedar
Incense cedar, rough sawn, naturally rot resistant, with the aromatic cedar smell. The best untreated option for beds and borders in constant soil contact. Rot resistance lives in the heartwood - sapwood weathers like any other softwood. Cedar is softer than Douglas Fir, so it suits beds and edging better than a wall holding back real load.

Pressure-Treated Lumber
ACQ-treated stock and incised Hem Fir - the longest-lasting option for in-ground use. Specify ground-contact rated material; above-ground-rated treated lumber is not the same thing and won't last buried. Call us for current sizes and pricing.

Reclaimed Timbers
Weathered, characterful stock with checking, nail holes, and patina already earned. Ideal when you want a wall that looks like it's been there for decades. Reclaimed varies piece to piece, so order some overage and expect to sort.

Lodgepole Pine Logs & Rails and Hand-Peeled Logs
Round rather than square. Peeled logs and rails give a rustic, mountain-cabin edge to beds and drives, and read very differently from a squared timber wall. Good for borders and definition, not for structural retention.

Douglas Fir #2 Lumber and Dunnage
The economical end. #2 Douglas Fir is sound construction-grade material with more knots. Dunnage is rough-sawn pine/spruce blocking in 4x4 and 6x6 at eight feet - inexpensive and utilitarian, fine for temporary beds, staging, or borders you expect to replace.

What actually makes landscape timber last

Rot is a moisture problem before it's a wood problem. Decay fungi need sustained moisture in the wood to get established, and the timbers that fail first are almost always the ones sitting in wet soil with nowhere for water to go. Four things extend service life more than species choice alone:

• Drainage behind the wall. Free-draining gravel backfill and a perforated drain line at the base do more for longevity than any coating. Water that can't sit against the wood can't rot it.
• A gravel base course. Set the bottom course on compacted gravel, not bare soil. It keeps the timber out of standing water and gives you a flat, level start.
• Sealing cut ends. End grain drinks water far faster than face grain. Every fresh cut - and every bore hole for rebar or a spike - should be treated. Cobra Rods are borate preservative rods made for exactly this: inserted into decay-prone areas and exposed end grain, they release preservative when moisture is present.
• A finish that blocks UV. Sunlight breaks down the surface lignin, which is what grays the wood and opens the checks that let water in. UV Guard Deck & Fence Wood Finish is a semi-transparent exterior finish built for this; Transformation Stain Log & Timber is the heavier-duty option and the one for restoring timber that's already weathered.

Browse the full range in Stain & Seal and Wood Rot Prevention & Repair.

Fastening and pinning

Rebar pins drive vertically through drilled holes to tie courses to each other and to the ground, with the bottom course pinned into undisturbed soil. Drill slightly under the rebar diameter so the pin bites.

Structural screws handle wood-to-wood connections, deadmen, and corners. Unlike lag bolts, modern structural screws install without pre-drilling:

• Starborn F19 - heavy-duty framing and timber connections.
• Starborn H19 - general wood-to-wood work in decking, fencing, and timber frame.
• Starborn H23 - ledger and rim connections.

Use hot-dip galvanized or stainless fasteners in any wall that stays wet, and match the fastener to the treatment - ACQ pressure-treated lumber is corrosive to ordinary zinc-plated steel.

Estimating what you need

For a straight wall the math is short. Timbers per course is wall length divided by timber length, rounded up. Courses is finished height divided by timber height. Multiply the two, then add about 10% for cuts, corners, and deadmen.

A 24-foot wall, 24 inches tall, built from 6x6 x 12' timbers: two timbers per course, four courses, so eight timbers - call it nine with overage. Add material for deadmen, the timbers that run back into the hillside to tie the wall into the slope, on anything above two courses.

Terraced beds and curved borders eat more material than the straight-line math suggests. When in doubt, order the overage - it's cheaper than a second delivery.

A note on wall height

Most jurisdictions set a threshold - often four feet from the bottom of the footing to the top of the wall - above which a retaining wall needs an engineered design and a permit. Surcharge loads change that too: a wall holding back a driveway, a slope, or a structure is a different problem than one holding back a garden. Check with your local building department before you build, and involve an engineer for anything tall or loaded. We can supply material for a wall of any size; we can't tell you what your jurisdiction will approve.

Related products

Shop Timber · Wood Products · Vigas, Latillas, Poles & Logs · Stain & Seal · Timbers & Beams

Frequently asked questions

What size timber should I use for a retaining wall?
6x6 is the workhorse for walls up to a couple of feet. Go to 8x8 or larger for taller walls, heavier loads, or a more substantial look. Anything above roughly four feet generally needs an engineered design - check your local code.

Do landscape timbers need to be pressure treated?
Not necessarily. Pressure-treated material lasts longest in direct soil contact, but cedar heartwood is naturally rot resistant, and Douglas Fir performs well when it's sealed, drained, and kept off wet ground. Drainage matters more than treatment on most projects.

How long do landscape timbers last?
It depends far more on drainage and detailing than on species. Timbers sitting in wet soil fail early regardless of material; timbers set on gravel, backfilled with drainage rock, with sealed cut ends and a UV-blocking finish, last many times longer.

Can you cut custom sizes and lengths?
Yes. We mill to spec, with logs lathe-milled up to 32 ft and hand-peeled up to 50 ft, and handle everything from a few timbers to large volumes.

Do you deliver?
Yes - across Utah and the Mountain West, and we ship nationwide. Many items ship in 1-3 days; larger timbers and special sizes run one to two weeks. Long timbers and full bundles need room for the truck and usually equipment to offload, so tell us about site access when you order.