How tall can I build without a permit?

Most jurisdictions allow timber retaining walls up to 4 feet tall without engineering or a permit.

How long does a timber retaining wall last?

Properly built with ground-contact-rated treated lumber, a timber retaining wall can last 15 to 20 years.

Do I need drainage behind the wall?

Yes, drainage is essential. Without it, water pressure builds and causes failure. Install perforated drain pipe and 12 inches of gravel.

How to Build a Retaining Wall | Lumberama

intermediate

2-3 days

$500 - $1,200

How to Build a Retaining Wall: Timber Construction Guide (2026)

Reviewed by Lumberama's Building Projects Team

|Last updated May 26, 2026

A timber retaining wall is a practical solution for controlling erosion, leveling a sloped yard, and creating usable outdoor space. Using landscape timbers or treated lumber, you can build an attractive wall up to 4 feet tall that holds back soil and transforms problem slopes into terraced planting beds.

Key Takeaways

A timber retaining wall is a practical solution for controlling erosion, leveling a sloped yard, and creating usable outdoor space.
Using landscape timbers or treated lumber, you can build an attractive wall up to 4 feet tall that holds back soil and transforms problem slopes into terraced planting beds.
Use only ground-contact-rated pressure-treated lumber (UC4A or higher).
Install a deadman anchor every 4 feet to resist soil pressure.
Never skip the drainage since water buildup is the number one cause of wall failure.

Tools Needed

circular saw, reciprocating saw, drill/driver with long bit, sledgehammer, hand tamper or plate compactor, level, tape measure, line level, shovel, wheelbarrow

Materials List

6x6 pressure-treated timbers or landscape timbers, 1/2-inch rebar (3-foot lengths), 12-inch galvanized spikes, filter fabric (landscape fabric), 3/4-inch gravel, 4-inch perforated drain pipe, 4-inch solid drain pipe (outlet), construction adhesive

Step-by-Step Instructions

Excavate and Level the Base

Dig a trench 6 inches deep and 12 inches wider than the timber. Compact soil, add 3 inches of gravel, and compact again.

Lay the First Course

Set the first row of timbers in the gravel trench, checking for level. Drill through timbers and drive 3-foot rebar stakes into the ground.

Stack Subsequent Courses

Stagger joints like a brick pattern. Connect each course with 12-inch galvanized spikes and construction adhesive.

Install Deadmen Anchors

Every 4 feet and every other course, install T-shaped timber deadmen extending 4-6 feet back into the slope.

Install Drainage System

Line back of wall with filter fabric. Lay 4-inch perforated drain pipe at the base. Backfill with 12 inches of gravel.

Cap and Finish

Install cap course with construction adhesive. Wrap filter fabric over gravel before adding topsoil. Grade to direct surface water away.

Recommended Species

Pressure-Treated Pine (rated for ground contact, UC4A or higher), Douglas Fir (treated)

Recommended Sizes

6x6 timbers (wall courses), 6x6 deadmen, 1/2-inch rebar

Pro Tips

Use only ground-contact-rated pressure-treated lumber (UC4A or higher). Install a deadman anchor every 4 feet to resist soil pressure. Never skip the drainage since water buildup is the number one cause of wall failure. Walls over 4 feet generally require engineering and a permit.