Build a retaining wall.

Retaining walls are not garden walls — they hold back earth, water, and load, and their failure modes are dramatic. A retaining wall that collapses can take a hillside down with it. This guide covers what brick retaining walls actually cost in 2026, when you need a structural engineer, and the drainage detail that separates a 30-year wall from a 3-year liability.

The single biggest mistake on retaining walls is missing drainage — water pressure behind the wall is what fails 80% of failed retaining structures in the UK.

What Does the Work Involve?

• Survey and load calculation — soil type, retained height, surcharge from adjacent structures.
• Engineer-stamped design for walls over 1 m.
• Deep strip foundation — typically 600 mm wide × 300–450 mm deep depending on load.
• Brick wall built with engineering bricks for the bottom 3–4 courses.
• Geotextile membrane and free-draining stone backfill behind the wall.
• French drain or weep holes at the base to release water pressure.
• Top coping to prevent water ingress into the wall structure.

Typical Costs

Retaining walls are 50–80% more expensive per linear m than garden walls of the same height because of foundations, drainage, and reinforcement.

How Long Does It Take?

• 10 m of 1 m wall: 1.5–2 weeks inc. drainage.
• 10 m of 1.5 m wall: 2–3 weeks.
• Engineer design + planning: 4–8 weeks before work starts.

DIY or Professional?

Specialist work only. Retaining walls fail dramatically — taking soil, structures, and sometimes people with them. Always hire experienced bricklayers with retaining-wall portfolios and use structural-engineer design for anything over 1 m.

Choosing the Right Tradesperson

• Look for retaining wall jobs in their portfolio, ideally aged 5+ years.
• Insist on a structural engineer's design for walls over 1 m.
• Confirm drainage strategy — geotextile + free-draining backfill + drainage outlet.
• Get foundation depth specified in writing.
• 10-year warranty on structural integrity is standard.

UK Regulations

• Retaining walls over 1 m need engineer-stamped design.
• Walls on or near boundaries trigger Party Wall Act obligations.
• Building Control may need to inspect significant retaining works.
• Listed properties and conservation areas have strict consent requirements.

Common Problems

• Wall bulging or leaning — almost always water pressure from missing drainage.
• Mortar joints crumbling — water ingress + frost. Sealed coping prevents.
• Foundation failure — undersized for the load. Engineer-designed foundations prevent.
• Frost heave — foundation not deep enough.
• Wall pulling away from house — differential settlement; ties to existing structure or independent foundation needed.

Frequently Asked Questions