How to Build a Garden Wall

Tools and Materials

Before You Start

• Check for underground services before digging foundations
• Confirm whether planning permission or party wall agreement is required
• Set out the wall line with pegs and string to check alignment
• Order 5-10% extra blocks/bricks for cuts and breakages
• Check the weather forecast — do not build in frost or heavy rain

Step-by-Step Construction

1. Step 1 — Excavate the foundation trench. Dig to the required depth (300-450 mm) and width (wall width plus 300 mm). Level the base of the trench and compact the soil.
2. Step 2 — Pour the concrete foundation. Mix C20 concrete (1:2:4 cement:sand:aggregate) and pour into the trench to a depth of at least 150 mm. Level the surface and allow to cure for 24 hours minimum.
3. Step 3 — Set out the first course dry. Lay the first course of blocks or bricks without mortar to check the layout, spacing, and any cuts needed. Mark the positions on the foundation.
4. Step 4 — Lay the DPC. Apply a mortar bed (10 mm) on the foundation at least 150 mm above finished ground level. Lay the DPC strip across the full width, overlapping any joins by 100 mm.
5. Step 5 — Build up corners first. Build corners (quoins) 4-5 courses high, checking plumb and level on each course. Use a gauge rod to ensure consistent 75 mm course heights (65 mm brick + 10 mm mortar).
6. Step 6 — Fill in between corners. Stretch a builder's line between corners at each course height. Lay blocks or bricks to the line, maintaining a stretcher bond pattern with 10 mm joints.
7. Step 7 — Point the joints. When the mortar is "thumbprint hard" (typically 1-2 hours after laying), finish the joints with a jointing iron. Use a bucket-handle or weathered joint profile for exposed walls.
8. Step 8 — Fit coping stones. Bed coping stones on a full mortar bed with a 25 mm overhang on each side. Point the joints between copings. Check level across the entire length.

Common Mistakes

• Foundations too shallow on clay — clay heave will crack the wall
• Forgetting the DPC — rising damp will cause efflorescence and frost damage
• Inconsistent mortar joints — use a gauge rod and line for every course
• Building too many courses in one session — mortar needs time to set, maximum 6-8 courses per day
• Not providing expansion joints — walls over 6 m long need 10 mm expansion joints
• No coping — exposed wall tops absorb water and suffer frost damage

Cost Estimate (2026)

Related Calculators

Use the Block Calculator for quantities, the Mortar Calculator for mortar volumes, and the Foundation Calculator for concrete requirements.