Garden Wall Calculator — Bricks, Mortar & Foundations

For a half-brick (single skin) wall, you need approximately 60 bricks per square metre. For a full-brick (one brick thick) wall, you need approximately 120 bricks per m². These figures include 10mm mortar joints and are based on standard UK bricks (215mm x 102.5mm x 65mm). Add extra bricks for piers — 4 bricks per course per pier.

Under UK permitted development rights, you can build a garden wall up to 1 metre high if it fronts a highway used by vehicles, or up to 2 metres elsewhere, without planning permission. Structural limits also apply: as a conservative rule of thumb a half-brick (single-skin) freestanding wall should not exceed about 450mm without piers, though the real safe height depends on wind exposure (roughly 375mm in exposed locations to 525mm sheltered, per BRE Good Building Guide 14 / PD 6697). Always check with your local planning authority.

Yes, all freestanding garden walls need a concrete strip foundation. For walls up to 1 metre high, the minimum foundation is 450mm wide and 225mm deep. For higher walls, increase the foundation proportionally. The foundation should be at least twice the width of the wall and be built on firm, undisturbed ground below the topsoil.

As good practice, piers are spaced at maximum 3 metre centres along a garden wall, plus one at each end (BRE Good Building Guide 14). For half-brick (single-skin) walls, piers are needed for any wall above roughly 450mm high. Piers are built by bonding an extra half-brick width into the wall at regular intervals, creating a thicker, stronger section that resists wind loading. This calculator allows a conservative extra 4 bricks per course per pier, which slightly over-orders to cover the bond and cutting waste.

For garden walls in sheltered positions a 1:6 cement to sand mix (one part cement to six parts building sand) is common practice. For exposed positions or below damp-proof course level use a stronger 1:4 mix. In NHBC / BS EN 998-2 terms these correspond roughly to mortar designation iii (M4, e.g. air-entrained 1:1:5½ cement:lime:sand) for general work and a stronger designation ii (M6) for exposed and below-DPC brickwork. Add plasticiser to improve workability if you are not using lime. Use sharp sand for foundation concrete and soft building sand for bricklaying mortar.

Yes, coping stones are strongly recommended on top of a garden wall. They shed rainwater away from the wall, preventing water from soaking into the brickwork and causing frost damage. Common coping options include twice-weathered concrete coping, bullnose brick-on-edge, and natural stone coping. Coping should overhang the wall by at least 25mm on each side.