Building a solid wood retaining wall can add visual interest and functionality to your landscaping. With the right planning and materials, you can create a beautiful, long-lasting retaining wall using wood. This guide will walk you through the entire process of building a solid wood retaining wall, from choosing the right location and designing the wall to preparing the site, selecting materials, building the wall, and finishing touches. Follow these steps and tips to build a stunning wood retaining wall for your yard.
Choose the Right Location for the Retaining Wall
When deciding where to build your retaining wall, consider these factors:
Slope and grade – The wall should be built on a slope to actually retain soil and “hold back” the hillside. Evaluate the grade to determine the appropriate height. Steeper slopes will require a taller wall.
Purpose – Think about the retaining wall’s purpose. Is it primarily decorative or meant to prevent erosion and maintain the slope? This will inform choices like materials and design.
Sunlight -Wood retains its strength longer when protected from excessive sun. North- or east-facing slopes are best. Avoid south or west if possible.
Drainage– Allow room for drainage, as wet soil retained behind the wall adds pressure. Locate the wall above the grade rather than below to improve drainage.
Property lines and permits – Check property lines and ordinances regarding size/height restrictions. Some areas require permits for walls over 4 feet.
Future plans – Consider future plans for the space, like patios or other landscaping that could integrate with the wall.
Choose a Retaining Wall Design
Once you’ve determined the perfect location, start planning the design. Consider the following:
Height – Recommended maximum heights for wood retaining walls are usually 4 feet for unreinforced walls, 6 feet if reinforced with geogrid.
Length – For longer spans, include reinforcement and/or regular breaks to relieve pressure. Maximum recommended span for wood is generally 10-15 feet.
Shape – Curved and tiered walls require more planning but provide added visual interest. Simple straight or L-shaped walls are easier for DIY builds.
Wood type – Hardy, rot-resistant woods like cedar and redwood are best. Pressure-treated pine is cheaper but more prone to rot over time.
Style – Rustic, natural wood or a refined look with capstones? Match the wall style to your landscape.
Slopes and terraces – Steeper, multi-level slopes often benefit from terraced retaining walls separated by planted slopes.
Features – Incorporate design features like planter boxes, benches, or staircases for added functionality and aesthetics.
Prepare the Building Site
Proper site preparation is crucial for building a solid, level wall that will stand the test of time:
Mark layout – Stake out the wall’s footprint and dig a 6-12 inch deep trench along the length of the wall.
Excavate – Remove all topsoil/organic material from the trench and dig down to solid native soil or compacted fill.
Add fill – Fill the trench with compactable gravel and tamp thoroughly to create a solid, level base.
Grade – The bottom of the trench should be angled slightly back towards the slope for drainage.
Gravel base – Add 4-6 inches of gravel base and pack it down. Compact the entire area thoroughly.
Drainage – Incorporate drainage as needed. Gravel backfill improves drainage, or install perforated PVC or weeping tile.
Erosion control – Use temporary measures like silt fence if needed to prevent erosion during the build.
Choose Wall Materials
Select quality materials that will hold up over time:
Wood
The main structural beams should be rot-resistant – cedar and redwood are great choices. Use 6×6 beams for 4 foot walls, 8×8 for higher spans. Pressure-treated pine is more prone to rot but is inexpensive. Seal all wood ends.
Posts
Vertical posts attached to beams provide reinforcement. Use 4×4 or 6×6 posts every 4-6 feet. Embed posts 2 feet into compacted gravel and attach to beams.
Gravel and Drainage Materials
3/4 inch gravel for the base, crushed rock for drainage behind the wall. Weeping tile or perforated PVC can also assist drainage.
Landscape Fabric
Install fabric between the backfill and the structural wall to prevent soil from leaking through. Use an outdoor grade fabric resistant to rot.
Reinforcement (for walls >4 feet)
Add geogrid or mesh reinforcement according to height – consult manufacturer specifications.
Capstones
Capstones distribute pressure evenly across the top of the wall. Limestone, granite, or precast concrete are common choices.
Build the Retaining Wall
Once planning is complete and site prepared, it’s time to start construction:
Set posts – Dig post holes and set posts 2 feet into the gravel base, spaced 4-6 feet apart.
Attach beams – Place the first course of beams on top of the posts. Attach with lag screws and construction adhesive.
Backfill – Backfill behind with drainage gravel, tamping down firmly every 6 inches.
Add reinforcement – For higher walls, at this point add geogrid or mesh reinforcement according to manufacturer specs.
Repeat – Stack subsequent courses of beams, alternating seams and attaching securely. Backfill after each course.
Capstones – Finish the top of the wall with capstones cut flush with beams to disperse pressure evenly.
Final backfill – Backfill the last 1-2 feet behind the wall with compacted fill or topsoil and pack firmly.
Drainage – Ensure drainage, directing water away from the wall and slope. Install weeping tile if desired.
Landscaping – Allow 2-4 weeks for the soil to settle before landscaping behind the wall.
Tips for Building a Strong, Durable Wood Retaining Wall
Follow these tips and best practices as you build:
- Stagger beam seams from row to row for added strength.
- Use the largest beam size suitable for the height.
- Embed posts at least 2 feet into compacted gravel and attach securely to beams.
- Install reinforcement like geogrid per manufacturer instructions for walls higher than 4 feet.
- Compact backfill in 6 inch layers as you stack courses.
- Angle the gravel base slightly back into the slope for drainage.
- Leave 1-2 feet of space between the wall and slope to backfill.
- Direct water and drainage away from the slope.
- Allow beams to acclimate to the climate before building if possible.
- Use weather resistant, treated lumber rated for ground contact.
- Seal wood post bottoms and all beam ends with water repellent.
- Don’t make curves or tiers too tight/steep – keep the design simple.
- Prevent erosion during the build with silt fence or other barriers.
- Wait for the ground to settle before landscaping behind the wall.
Frequently Asked Questions
How deep should I dig the gravel base?
Dig a trench 12-24 inches deep, leaving 8-12 inches of space to add compacted gravel base.
Can I build a wood retaining wall on a concrete base?
Yes, a poured concrete footing can provide a sturdy alternative to the gravel base.
What is the maximum height for a wood retaining wall?
Unreinforced walls should be limited to 4 feet tall. With geogrid reinforcement they can reach 6-8 feet safely.
How far apart should wood posts be spaced?
Wood posts should be installed every 4 to 6 feet along the length of the wall for support.
Should backfill be compacted?
Yes, it’s crucial to compact backfill in layers as you stack courses, using a hand tamper. This prevents settling.
How do I prevent erosion with a wood retaining wall?
Allow room between the wall and slope for backfill. Direct drainage away from the slope. Use barriers like silt fence during construction.
What maintenance does a wood retaining wall require?
Occasional checking for rot, replacing damaged boards, and keeping drainage functional. A sealant helps preserve wood.
Conclusion
Building a solid wood retaining wall takes careful planning, appropriate materials, proper construction techniques, and some hard work. But the end result is a beautiful, functional structure that lends visual interest and dimension to the landscape. Durable, rot-resistant woods like cedar and redwood create long-lasting retaining walls that make a graceful statement in any yard or garden. Follow this guide to plan and construct your own spectacular wood retaining wall. Be sure to prepare the base properly, use the right materials, and employ reinforcement and drainage as needed. With attention to detail, you can create a retaining wall that seamlessly blends strength, function, and aesthetic appeal.
How to Build a Solid Wood Retaining Wall
Planning is key when building a wood retaining wall. Follow these steps to ensure your wall stands the test of time:
- Evaluate the slope and choose an appropriate location
- Design the wall, considering height, length, shape and style
- Prepare the site by excavating, adding fill, compacting the base
- Select quality wood and materials like posts, gravel, reinforcement
- Stagger and stack the beams, backfilling after each course
- Install capstones and drainage
- Allow the ground to settle before landscaping
A properly constructed wood wall provides beauty, functionality and added dimension to outdoor spaces. With smart planning, meticulous construction, and the right materials, you can create a stunning wood retaining wall for your yard. Follow the tips outlined here for best results.