How many sleepers do I need for a retaining wall?

The number of sleepers depends on wall length, height and sleeper size. Standard new softwood sleepers are 2.4m x 200mm x 100mm. For a 1m high wall, you need 5 courses. Multiply courses by the number of sleepers per course (wall length / 2.4m). A 5m x 1m wall needs approximately 15 sleepers plus 10% wastage.

Do sleeper walls need rebar pins?

Yes, steel rebar pins (12-16mm diameter) are driven vertically through pre-drilled holes in the sleepers and into the ground below. They hold the courses together and prevent the wall from moving. Space pins at 600mm centres along the wall, with each pin long enough to pass through all courses and 450mm into the ground.

How high can a sleeper retaining wall be?

Freestanding sleeper walls up to 600mm are generally straightforward. Walls up to 1m need rebar pins and good drainage. Walls over 1m retaining soil should have engineering input — they may need deadman anchors, deeper foundations or a stepped design. Building Regulations may apply for walls over 1.2m retaining soil.

What drainage do I need behind a sleeper wall?

Essential: 150mm of clean gravel (20mm shingle) behind the full height of the wall, wrapped in geotextile to prevent soil clogging. Install 50mm weep pipes through the wall at 1-1.2m centres along the bottom course. Without drainage, water pressure builds behind the wall and can cause failure.

Can I use recycled railway sleepers for retaining walls?

Recycled railway sleepers (hardwood, typically 2.6m × 250mm × 125mm) are very strong but may contain creosote, which is now restricted for domestic use under EU/UK regulations. New softwood sleepers (pressure-treated to UC4) are the recommended alternative for garden use. Oak sleepers are premium but more expensive.

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Sleeper Retaining Wall Calculator — Sleepers, Rebar & Drainage

Calculate sleeper count, rebar pins, drainage gravel and weep pipes for a timber sleeper retaining wall.

Wall Length

Wall Height

Sleeper Type

Sleeper Price

Rebar Price

How We Calculate This

This calculator determines the number of sleepers, rebar pins, drainage gravel and weep pipes for a timber sleeper retaining wall.

Sleeper count

Courses = ceil(Wall Height / Sleeper Height)
Sleepers per course = ceil(Wall Length / Sleeper Length)
Total = Courses x Per Course x (1 + Wastage%)

Rebar pins

Pins = ceil(Wall Length / Spacing) + 1
Pin length = wall height + 450mm embedment. Typical spacing 600mm centres with 12mm rebar.

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.