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Retaining walls

Heights that demand structural design, drainage, geogrid, sleepers.

All guides
Stub — growing
Last reviewed
2 sources
Regulations
  • Retaining walls over 1 m generally need structural design and may need building control approval where they retain ground next to a building or footpath. [1]
  • Walls on or near a boundary are also covered by the Party Wall etc. Act 1996 in some cases. [2]
Hints & tips
  • Before excavating the wall trench or driving any soldier piles — CAT & Genny sweep (HSE HSG47). Retaining walls often run along boundaries where services hide. Full method in the Safety guide.
  • Always provide drainage behind the wall — 100 mm perforated land drain, clean stone backfill, geotextile separator.
  • Sleeper walls in oak or treated softwood: 200×100 sleepers max 600 mm high stacked, 1000 mm with steel posts driven into concrete pads.
  • Allow a batter (lean back) of 1:10 on dry-stone or gabion walls.
  • Surcharge from a driveway above doubles the lateral loads — never DIY a retaining wall holding back a vehicle.
  • On clay subgrades the active earth pressure roughly doubles when saturated — design walls over 600 mm with a structural engineer, not from a YouTube video.
  • Steep sites benefit from terracing into two lower walls instead of one tall wall — halves the loads, no structural design needed.

This app provides general UK guidance and material estimates only. It is not legal, planning, engineering or building-control advice. Always confirm requirements with your local planning authority, building control, utility providers, manufacturers or qualified professionals.