LND/Specific/TBT-LND-007

Retaining Wall Construction (Landscape)

Landscaping & External Works › Specific › Retaining Wall Construction (Landscape)

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Landscape retaining walls hold back earth on sloped sites using concrete blocks, stone, timber, or gabions.
Even low walls retain significant earth pressure — a 1.5 metre wall retains several tonnes of soil.
Excavation for wall foundations creates trench collapse risk, especially in soft or wet ground.
Heavy block and stone handling is repetitive — musculoskeletal injuries are common among installers.
Drainage behind the wall is critical — water build-up doubles the lateral pressure and causes failure.
Walls over 1.2 metres typically require structural design and building regulations approval.
CDM 2015 applies to retaining wall projects where construction work is being carried out.
Temporary support of the excavated face may be needed while the wall is being constructed.
The finished wall must withstand surcharge loads from vehicles, structures, or stored materials above.
Backfilling must use free-draining material placed and compacted in accordance with the design.

Collapse risk	Retaining walls that fail under earth pressure collapse suddenly, burying workers.
Excavation hazard	Foundation trenches for walls create the same collapse risks as any other excavation.
Manual handling	Heavy block and stone lifting causes chronic back injuries without mechanical aids.
Drainage failure	Water accumulation behind walls without drainage causes catastrophic structural failure.

Don't

Ensure walls over 1.2 metres have a structural design and building regulations approval.
Support excavation faces while constructing the wall foundation and lower courses.
Install drainage behind the wall as specified — filter fabric, pipe, and free-draining fill.
Use mechanical aids for lifting heavy blocks, stone, and precast elements.
Compact backfill in layers as specified in the design to prevent settlement.
Check the foundation bearing capacity before starting wall construction.
Follow the manufacturer's installation guide for proprietary retaining wall systems.
Keep surcharge loads back from the wall crest during and after construction.
Inspect the wall after heavy rainfall for signs of movement, cracking, or bulging.
Wear gloves and use correct lifting technique for repetitive block handling.

DON'T build retaining walls over 1.2 metres without a structural design.
DON'T omit drainage behind the wall — water pressure will cause it to fail.
DON'T backfill with clay or unsuitable material that holds water against the wall.
DON'T compact backfill with heavy plant too close to the wall face.
DON'T lift heavy blocks and stone repeatedly without mechanical aids or rotation.
DON'T excavate foundations without assessing the need for trench support.
DON'T surcharge the ground behind the wall above the design loading.
DON'T leave the wall unsupported overnight before backfilling is complete.
DON'T ignore cracks, bulging, or weep hole blockage after construction.
DON'T build the wall higher than the approved design without engineering review.

See also: Landscaping Safety Awareness | Slope Stability Awareness

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