Timber crib wall repair

Timber crib wall failure

The main cause of the failure of timber crib walls is rotten timber headers that go from the front to the back of the crib frames.

The main causes of failure are:

• Poor-quality timber
• Poor-quality timber treatment
• Poor-quality stone fill
• No or blocked rear wall drainage

The main cause of the rot is poor infill stone that is full of fines. The material stays damp.

Timber crib walls are sold to last for 60 years. This is only the case if the timbers are treated correctly and the stone fill is allowed to drain.

From our experience, many walls have failed in less than twelve years.

Timber crib repair solutions

There are a number of repair options, and they all have pros and cons.

1. Demolish and rebuild
2. King post retaining wall
3. Gabion basket
4. Soil nail and earthbag face

The drier for the solution is cost and access to the wall.

Solution 1 – Demolish and rebuild

Demolish the existing timber crib wall, sort out the timber from the stone. Build a new concrete or plastic (eco crib) wall; use the existing stone if possible.

Pros

• Life span over 100 years

Cons

• Very expensive
• Requires permission from the retained earth land owner
• The retained earth land may have to be excavated to form a safe slope
• Requires good access for heavy plant

Solution 2 – King post retaining wall

Design and build a king post retaining wall at the toe of the existing timber crib wall.

Pros

• The existing wall can stay in place
• The wall is very slim 200 mm
• Over 100-year life span

Cons

• Requires clay, sand, silt, gravel type soils to 1.5 times the wall height
• Needs heavy plant and good access to drill the post holes
• Expensive but less expensive than the rebuild option
• Requires permission of retained earth land owner

Solution 3 – Gabion basket

Build a gabion basket against the existing timber crib wall. This option is good for wall up to 2m. The space used is 1m. Walls above 2m will use 2m of space.

Pros

• Simple to build, including DIY
• The most economical solution
• Life span 40 to 50 years
• Can be build with poor access

Cons

• Uses up a lot of space
• Only good up to 2m, using 1m of space, thereafter uses 2m and more space.

Solution 4 – Soil nail and earthbag face

A galvanised steel mesh is placed against the face of the timber crib wall and soil nails are driven into the retained earth. The soil nails take the shear curve of the retained earth to move further away from the face.

To protect the steel mesh and give a face to the wall a earthbag wall is built. The earthbags can then be seeded to form a vegetation wall.

Pros

• Only slightly more expensive than the gabion basket solution
• Life span in excess of 100 years when vegetated
• It can be built with poor access

Cons

• Requires a specialist contractor (but we know them)
• Requires permission of retained earth land owner

Timber crib budget repair costs

The cost to build the solutions is below:

1. Demolish and rebuild – £900 m2
2. King post retaining wall – £650 m2
3. Gabion basket – £400 m2 for up to 2m high walls
4. Soil nail and earthbag face – £480 m2

Cost index 2026

The costs are only a guide to illustrate the differences between the solutions. Some solutions use little space, some require good access, and others can be built with poor access.

The rates will change depending on the location, the project’s scale, and the risk the contractor may pose.

If you are not sure, get support

We recommend selecting the right solution for your site constraints, designing it, creating a budget, and preparing documents to obtain competitive prices from contractors. We can support you through the process.