Timber crib retaining wall
Timber crib retaining wall
A Timber crib retaining wall can look quite attractive. Timber crib is more economical than concrete criblock but has a shorter life span. (ten to sixty years)
Timber crib walls are simple to build with training or can be built using a specialist contractor.
A timber crib retaining wall is ideal for high retaining structures over 3m high. They are used in housing projects mainly.
A timber crib retaining wall is built using timber and stone. The timber is made into cribs (frames) 1.2m wide x 0.6m, 0.9m, 1.2m and 1.5m deep. Each crib is approximately 200mm high and are filled with stone.
The design principle is gravity, and the design is similar to a gabion basket.
Timber crib has a short life span. Although the timber is treated, we have seen failure within fifteen years.
Timber units
The timber units to make the cribs are called stretchers and headers. Stretchers run the length of the wall. Headers run from the front to the back on the wall. The stretchers and headers lock into each other using notches built into the headers.
Stretchers are 2.4m long whereas headers are 0.6, 0.9, 1.2 and 1.5m long.
Design
Free draining fill is required to backfill behind the criblock structure with a land drain at the bottom to reduce any risk from hydrostatic pressure.
The higher the wall design, the wider the frames need to be at the bottom of the wall.
Criblock walls are typically inclined to allow gravity to reduce the wall’s mass and keep the design economical.
Warning
Timber criblock walls have an agrement certificate showing a sixty-year lifetime, but the life span depends on the quality of the timber treatment, and the stone fill material.
We have many examples of timber criblock walls failing within twelve years of construction.
Read our page on timber crib failure and repair. Link below:
We include this page on the website as it is a solution, but we never recommend it.
If in doubt call us.
Timber crib design guide
| Height (mm) | 1200 | 1800 | 2400 | 3000 | 3600 | 4000 | 5000 |
|---|---|---|---|---|---|---|---|
| Crib Type | Timber | Timber | Timber | Timber | Timber | Timber | Timber |
| Stone Type | Limestone | Limestone | Limestone | Limestone | Limestone | Limestone | Limestone |
| Base Width (mm) | 800 | 800 | 1400 | 1600 | 1800 | 1900 | 2000 |
| Base Depth (mm) | 200 | 300 | 400 | 400 | 500 | 500 | 500 |
| Surcharge | 10kn/m² | 10kn/m² | 10kn/m² | 10kn/m² | 10kn/m² | 10kn/m² | 10kn/m² |
| Factor Of Safety | M=1.5 | M=1.5 | M=1.5 | M=1.5 | M=1.5 | M=1.5 | M=1.5 |
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The design table above has been created to allow us to build budget costs. The designs are indicative for timber crib walls based upon a base material with allowable bearing pressure of >200kPa.
The design uses well-graded, granular backfill with the back of the wall having drainage to relieve hydrostatic pressure.
All indicative information presented in this table is based upon assumed loading and ground conditions. This table is for guidance purposes only and will be subject to change following a detailed, site-specific design developed by an approved structural engineer.
Timber units
The timber units to make the cribs are called stretchers and headers. Stretchers run the length of the wall. Headers run from the front to the back on the wall. The stretchers and headers lock into each other using notches built into the headers.
Stretchers are 2.4m long whereas headers are 0.6, 0.9, 1.2 and 1.5m long.
| Units (mm) | Type | Weight (kg) |
|---|---|---|
| 600 | Headers | 0.85 |
| 900 | Headers | 1.28 |
| 1200 | Headers | 1.6 |
| 2400 | Stretchers | 4.8 |
Gallery of Timber crib retaining wall
Compare prices of retaining wall types
Which retaining wall type is the most economical to build? We have written a free guide on retaining wall price comparisons. The guide details the different types of retaining walls and gives you a price estimate of each type to compare.
Retaining wall price comparison guideTimber crib design service
The design of a retaining wall requires knowledge of the retaining material, the water table, the ground bearing capacity and any site constraints. The design requires a ground investigation and a structural engineer to ensure the design is fit for purpose.
We offer a full design service from carrying out the ground investigation to final working drawings.
Learn about our design serviceFAQs about Timber crib retaining wall
A criblock is a timber or concrete frame filled with stone to form a column.
The cost to build a timber crib retaining wall changes with the height of the wall, scale of project, location of the project and any site constraints.
We do have a comprehensive price table and budget calculator in our price guide. The price guide costs change over time so we keep it in one document.
You can download the document from this link. Get the price guide.
When the timber is treated correctly under quality conditions, it is said the timber will last for 60 years. However we have seen failures under fifteen years. Timber criblock is more competitive than concrete criblock but comes with a risk.