How to Build a Retaining Wall Using Timbers
A low retaining wall built with timbers follows many of the same construction steps as an interlocking block wall.
Overview
A low retaining wall built with timbers follows many of the same construction steps as an interlocking block wall. All steps specific to timber construction are shown here.
When built properly, a timber retaining wall can have a life span of 15 to 20 years. Be sure to use pressure-treated lumber rated for ground contact, and build the wall with 5 x 6 or larger timbers; 4 x 4 and 4 x 6 sizes are not strong enough for retaining walls. Avoid using old, discarded railroad ties that have been soaked in creosote, which can leach into the soil and kill plants.
Cut the timbers with a reciprocating saw and long wood blade (or a chain saw, if you prefer). Before building the retaining wall, prepare the site.
Timber retaining walls must be anchored with “deadmen” that extend from the wall back into the soil. Deadmen prevent the wall from sagging under the weight of the soil. For best results with timber retaining walls, create a backward angle (batter) by setting each row of timbers 1⁄2" behind the preceding row. The first row of timbers should be buried.
From: Complete Guide to Garden Walls & Fences, 978-1-58923-519-9
Step 1
Tips for Strengthening a Timber Retaining Wall
Install vertical anchor posts to reinforce the wall. Space the posts 3 ft. apart, and install them so the buried depth of each post is at least half the exposed height of the wall. Anchor posts are essential if it is not practical to install deadmen.
Step 2
How to Build a Retaining Wall Using Timbers
Spread a 6"-layer of compactable gravel subbase into the prepared trench, then tamp the subbase and begin laying timbers. Each row of timbers should be set with a 1⁄2" batter, and end joints should be staggered so they do not align.
Step 3
How to Build a Retaining Wall Using Timbers
Use 12" galvanized spikes or reinforcement bars to anchor the ends of each timber to the underlying timbers. Stagger the ends of the timbers to form strong corner joints. Drive additional spikes along the length of the timbers at 2-ft intervals. If you have trouble driving the spikes, drill pilot holes.
Step 4
How to Build a Retaining Wall Using Timbers
Install deadmen, spaced 4 ft. apart, midway up the wall. Build the deadmen by joining 3-ft-long lengths of timber with 12" spikes, then insert the ends through holes cut in the landscape fabric. Anchor deadmen to the wall with spikes. Install the remaining rows of timbers, and finish backfilling behind the wall.
Step 5
How to Build a Retaining Wall Using Timbers
Improve drainage by drilling weep holes through the second row of landscape timbers and into the gravel backfill using a spade bit. Space the holes 4 ft. apart, and angle them upward.
