Calculate timbers, spikes, and deadmen for a landscape timber retaining wall. Enter wall dimensions for a complete material list.
Timber retaining walls are one of the most popular DIY-friendly retaining wall options for walls up to 3 feet tall. Using pressure-treated 6×6 or 6×8 landscape timbers, these walls are relatively easy to build and provide a natural, rustic look.
This calculator estimates the number of timbers, rebar or spike connectors, and deadmen ties based on your wall dimensions. Each timber is typically 8 feet long and 6 inches tall, so a 3-foot wall requires 6 courses. Timbers are connected with 12-inch galvanized spikes or 1/2-inch rebar driven through pre-drilled holes.
Whether you're building a garden terrace, leveling a slope, or creating a raised bed border, this tool gives you an accurate material list for ordering and budgeting.
This measurement supports better project estimation, enabling contractors and engineers to deliver accurate bids and avoid costly overruns during the construction process. Precise calculations are essential for meeting regulatory requirements, passing inspections, and ensuring the long-term structural integrity and safety of the completed project.
Planning a timber retaining wall requires knowing how many timbers for each course, how many spikes to connect them, and how many deadmen to anchor the wall into the hillside. This calculator figures it all out from your wall length and height. Accurate figures enable contractors to prepare competitive bids with confidence, reducing the risk of underestimating costs or overcommitting on project timelines and deliverables.
Courses = Wall Height (in) ÷ Timber Height (in) Timbers per Course = Wall Length (ft) ÷ Timber Length (ft) Total Timbers = Courses × Timbers per Course + Deadmen Spikes = 2 per timber overlap + 2 per deadman
Result: 18 timbers + 3 deadmen = 21 total
A 24-ft wall at 3 ft high needs 6 courses (3 ft ÷ 6 in). Each course uses 3 timbers (24 ÷ 8). Total: 18 wall timbers + 3 deadmen (every 8 ft) = 21 timbers. Plus about 42 spikes for connections.
Excavate a level trench 6–12 inches deep. Add and compact 4–6 inches of gravel. Lay the first course half-buried. Drill and spike each course to the one below. Stagger joints by at least 2 feet. Install deadmen every 6–8 feet on courses 2–3.
Backfill behind the wall with 12 inches of crushed gravel. Install a 4-inch perforated pipe at the base, sloped to daylight at the wall ends. Cover the gravel with filter fabric to prevent soil migration, then backfill with native soil.
Timber retaining walls cost $10–$20 per sq ft of wall face (materials only). This compares to $15–$30 for block walls and $25–$50 for poured concrete. Labor adds 50–100% to material costs for professional installation.
Choose block or concrete for walls over 4 feet, heavy surcharge loads (driveways, structures), or permanent structures. Timber walls are best for garden terracing, landscape borders, and low retaining needs in residential settings.
Timber walls are suitable for heights up to 3–4 feet. Beyond 4 feet, timber walls lack the structural capacity and should be replaced with block, stone, or poured concrete walls. Always check local building codes.
Deadmen are timbers that extend perpendicular from the wall face into the hillside, anchoring the wall against soil pressure. They're typically a T-shape: one timber into the hill connected to a cross-timber for holding power.
Pressure-treated timbers last 15–20 years in ground contact. Older treatments like CCA last 30+ years. Modern ACQ/CA-B treatments last 15–25 years. Proper drainage significantly extends wall life.
Yes, always. Install 4–6 inches of crushed gravel backfill behind the wall with a 4-inch perforated drain pipe at the base. This prevents hydrostatic pressure, which is the #1 cause of retaining wall failure.
Most jurisdictions require a permit for retaining walls over 4 feet in total height (including buried portion). Some require permits for walls over 2 or 3 feet. Check your local building department before starting.
Use 12-inch galvanized landscape spikes or 1/2-inch rebar cut to 24-inch lengths. Place 2 spikes per timber end and one in the middle. For rebar, drill 9/16-inch holes and drive rebar through all courses.