Bricklaying Bonds & UK Brick Sizes

UK brickwork looks straightforward until you try to set out an opening, calculate quantities, or match existing bond. Getting the dimensions and bond pattern right from the outset avoids awkward cut-bricks, visual discontinuities and, in loadbearing work, structural weakness at perpends.

UK Brick Dimensions

The UK standard brick has a work size (the actual manufactured dimension, allowing for production tolerance) of:

• Length: 215 mm
• Width: 102.5 mm
• Height: 65 mm

Clay bricks are made to BS EN 771-1: Specification for clay masonry units and calcium silicate bricks to BS EN 771-2. BS EN 771-3 is a different part of the same standard and covers aggregate concrete masonry units, which is what you want for dense and lightweight blocks rather than for calcium silicate.¹ The 215 × 102.5 × 65 mm work size carried over from the former British Standard BS 3921; BS EN 771-1 changed how the size tolerance is tested.² Tolerance is judged on the mean of 10 bricks: for a standard brick, category T2 allows ±4 mm on length, ±3 mm on width and ±2 mm on height, and the looser T1 allows ±6, ±4 and ±3 mm.²

The coordinating size adds a nominal 10 mm mortar joint to each face, giving:³

• Length: 225 mm (215 + 10)
• Width: 112.5 mm (102.5 + 10)
• Height: 75 mm (65 + 10)

These coordinating dimensions are the numbers to use for setting out, walls, openings, reveals and piers should be multiples of 225 mm horizontally and 75 mm vertically wherever possible.

Courses Per Metre

With a 10 mm bed joint, each course occupies 75 mm of height. Therefore:

• 4 courses = 300 mm
• 1 metre height = 13.33 courses, in practice, 13 courses occupy 975 mm, so a 1 m lift requires a slightly thicker bed on the final course, or the spec should call up heights in 75 mm multiples.

A convenient rule of thumb: 4 courses per 300 mm, or 13 courses per 975 mm, rounding to 1 m with mortar adjustment.

Bricks Per m² and Cost

For standard-format brickwork you need about 60 bricks/m² for a single-skin (half-brick, 102.5 mm) wall (1 ÷ (0.225 × 0.075) = 59.3) and 120/m² for a one-brick (215 mm) wall, plus around 5% for cuts and waste. At 2026 prices, mid-range facing bricks run £0.70–£1.44 each (£700–£1,435 per 1,000), so the brick material alone for a single skin is roughly £44–£90/m² (63 bricks with waste); reclaimed and handmade bricks often cost more. Add mortar (about 0.02 m³/m²) and labour: a bricklayer typically charges £260–£340/day, the top of that range in London, and daily output varies widely with the amount of cutting and facework.

Mortar Joints

Two joint types govern the bond:

• Bed joint, horizontal joint between courses, typically 10 mm
• Perpend (perp), vertical joint between bricks in the same course, typically 10 mm

Perpends should be plumb and aligned across alternate courses in most bonds. Continuous vertical joints (a “straight joint” or “stack bond”) are structurally weak and should be avoided in loadbearing work unless reinforced.⁴

Principal Bricklaying Bonds

A bond is the pattern in which bricks are laid to ensure perpends in adjacent courses do not align (which would create a plane of weakness). The most common bonds in UK construction are:

Stretcher Bond

The standard bond for half-brick-thick (102.5 mm) walls, cavity wall outer leaves, partition walls, and facework. Each course shows only the stretcher (long face) of the brick, offset by half a brick (112.5 mm) from the course below. It is the simplest and most economical to lay.⁴

Bricks per m²: approximately 60 bricks, before a waste allowance of about 5%.

English Bond

Alternating courses of headers (brick laid across the wall, short face showing) and stretchers.⁴ Produces a strong one-brick-thick (215 mm) solid wall.⁴ Once the standard for loadbearing brick construction before the cavity wall became dominant. The header course ties the two-wythe thickness together without separate ties.

Bricks per m²: approximately 120 bricks (one-brick-thick wall, both faces combined).

Flemish Bond

Each course alternates headers and stretchers, with each header centred on the stretcher below, giving a richer decorative appearance than English bond.⁴ Structurally comparable but slightly weaker than English bond because headers and stretchers appear in every course rather than alternating complete courses. Common on Georgian and Victorian domestic facades.

Bricks per m²: approximately 120 bricks (one-brick-thick), same as English bond.

English Garden Wall Bond

Several courses of stretchers, most commonly three, between each course of headers.⁵ Faster and cheaper than full English bond, used where the full wall thickness is not needed for strength. Common on boundary and garden walls.

Header Bond

All bricks laid as headers. Used for curved work (the short dimension eases the curvature) and decorative detailing.⁴

Bricks and Bond at a Glance

Figures are net of waste: add about 5% for cutting, and for a project order a further 5% contingency for damaged bricks and future repairs.

Every bond in a one-brick (215 mm) wall uses about the same 120 bricks/m², because the volume of brick is the same; header bond is one of them, since each header spans the full thickness of the wall.⁴

Setting Out Openings

Window and door openings should ideally be set to brick co-ordinating sizes.⁶ For four bricks, makers’ dimension tables give 910 mm for an opening (bricks plus two joints), 900 mm for a panel with return ends (bricks plus one joint) and 890 mm for a pier (bricks only).³ Setting an opening at 910 mm rather than 900 mm gives a clean stretcher bond return with no awkward cuts. Non-modular openings force cut closers and can disrupt the bond across the elevation.

At reveals (the return face of an opening), a queen closer, a brick cut along its length to roughly half its width, is used to maintain the bond at the corner. Queen closers are placed next to the quoin (corner) header, not at the end of the course.

Mortar Specification

Mortar mix affects bond strength and durability. For facing brickwork on external cavity walls, a designation (iii) mortar, 1:1:6 cement:lime:sand, is standard for most applications.⁷ In severe exposure, such as copings, cappings and brickwork near ground level, a stronger designation (ii), 1:0.5:4.5 (M6), or even designation (i) may be advisable.⁸ Over-strong mortars (designation i) with high cement content can cause brick spalling by constraining thermal and moisture movement.

Mortar should comply with BS EN 998-2: Specification for masonry mortar.⁹ Pre-mixed retarded mortars are widely used on site for consistency; their working life, commonly about two working days, must be observed.¹⁰

UK Standards

• BS EN 771-1: Clay masonry units (bricks)¹¹
• BS EN 771-2: Calcium silicate masonry units¹²
• BS EN 998-2: Masonry mortar⁹
• BS EN 1996-1-1 (Eurocode 6): Structural design of masonry¹³
• BS 8000-3: Workmanship, code of practice for masonry (the 2001 edition was withdrawn in May 2020; use the current edition)¹⁴

Approved Document A (Structure) of the Building Regulations references Eurocode 6 and its National Annex for loadbearing masonry design.⁷ For straightforward domestic work, the deemed-to-satisfy tables in the document cover most standard situations without a full structural calculation.

The rules in this note are those that apply in England. Scotland, Wales and Northern Ireland have their own building standards and permitted development rights.