Brick Types Guide: Engineering, Common, Facing and Handmade — Selecting for the Right Application

Summary

Brick selection is one of the most consequential decisions on any masonry construction project. The wrong brick in the wrong application leads to: freeze-thaw spalling in exposed positions, efflorescence from inappropriate salt content, structural failure in high-load applications, and aesthetic failure when a facing brick weathers poorly. Yet many projects specify bricks based on colour and price alone, ignoring the technical classification system that determines actual performance.

BS EN 771-1 (the European standard for fired clay bricks, which replaced BS 3921 in the UK) provides a comprehensive classification system. Understanding this system allows accurate specification of bricks for any application — from a garden wall to a multi-storey structural frame. This article covers the key classification parameters, the main brick types available in the UK market, and their appropriate applications.

Key Facts

• BS EN 771-1 — European standard for fired clay masonry units (bricks); defines classification, marking, and test methods
• Standard UK brick size — 215mm × 102.5mm × 65mm (nominal, excluding joints); 10mm bed joint = 75mm coursing
• Engineering brick Class A — highest performance; compressive strength ≥125 N/mm²; water absorption ≤4.5% by weight; Staffordshire Blue and similar
• Engineering brick Class B — compressive strength ≥75 N/mm²; water absorption ≤7%; common fletton engineering quality
• Frost resistance F2 — highest frost resistance; tested to withstand 25 freeze-thaw cycles; required for all fully exposed locations (copings, paving)
• Frost resistance F1 — moderate frost resistance; for sheltered or partially sheltered positions
• Frost resistance F0 — no freeze-thaw resistance; indoor use only
• Water absorption T — total water absorption up to 6% by mass; denser, lower absorption
• Water absorption M — total water absorption between 6–12%; medium absorption
• Water absorption S — total water absorption above 12%; high absorption; rural/reclaimed types
• Soluble salt S2 — low soluble salt content; required for all external work to avoid efflorescence
• Soluble salt S1 — higher salt content; acceptable for protected positions
• Calcium silicate bricks — BS EN 771-2; manufactured from sand and lime; uniform appearance; no frost resistance classification (equivalent to F2); white or light grey colour
• Concrete bricks — BS EN 771-3; dense aggregate concrete; used as commons in block work; available in facing grades

Quick Reference Table

Detailed Guidance

Engineering Bricks

Engineering bricks are the workhorses of the brick world — dense, strong, and virtually impermeable. They are the correct specification for any application where structural loads, moisture resistance, or chemical attack are primary concerns:

Class A Staffordshire Blue Engineering Brick:

• Minimum compressive strength: 125 N/mm²
• Maximum water absorption: 4.5% by mass
• Frost resistance: F2 (highest)
• The distinctive blue-black colour comes from the vitrification process (fired at very high temperature)
• Traditional use: Victorian engineering works — sewers, bridges, basements, paviors
• Modern use: below DPC, retaining walls, damp-prone areas, paving, copings on garden walls
• Do not use without DPC between engineering bricks and softer facing bricks — differential movement can cause cracking

Class B Engineering Brick:

• Minimum compressive strength: 75 N/mm²
• Maximum water absorption: 7%
• More commonly available in red/brown as well as blue
• Suitable for: DPC courses, below-ground work, hard landscaping where Class A is unnecessary
• More affordable than Class A while still exceeding most structural load requirements

Applications where engineering bricks are required:

• All brickwork below DPC (in contact with or near ground moisture)
• Copings and cappings on external walls
• Retaining walls in contact with soil
• Drainage channels and gullies
• Steps and paviors in high-traffic areas
• Parapets (upper courses) in highly exposed locations

Common Bricks

Common bricks (sometimes called commons) are workmanlike bricks without decorative face quality requirements. They have no BS EN 771-1 appearance classification:

• Used for internal work, backing courses, filling, and any position not visible in the finished work
• Flettons (London Brick Company) are the classic UK common brick — made from Jurassic shale, kilned at relatively low temperature
• Flettons have a characteristic pale pinkish-orange colour with sand-rolled faces on some surfaces
• Not suitable for exposed external faces without protection (plaster, render, or cladding)
• Not suitable for below-DPC applications — high water absorption and low frost resistance
• Calcium silicate common blocks are a modern alternative; dimensionally accurate

Facing Bricks

Facing bricks are specified primarily for their appearance. They must have:

• A high-quality face texture and colour consistency
• Adequate frost resistance for the exposure category
• Low enough soluble salt content to avoid efflorescence

Wire-cut facing bricks:

• Extruded clay column cut to brick size by wires
• Clean, precise arrises
• Wide range of colours (buff, red, brown, multi)
• Available in hand-thrown texture variations
• Most modern facing bricks are wire-cut

Extruded (pressed) facing bricks:

• Clay column pressed in a mould to give crisp geometry
• More uniform than handmade; less lively appearance
• Standard choice for contract housing

Handmade facing bricks:

• Each brick formed by hand in a mould; distinctive slight irregularities, colour variation, and 'crease' texture
• Premium product; used for heritage work, high-end residential, and where character is required
• Wire cut can mimic handmade texture to varying degrees of success — check samples carefully
• Slower production; longer lead times; higher cost (typically 2–4× wire-cut price per brick)

Selecting facing bricks for exposure:

Reclaimed Bricks

Reclaimed bricks are salvaged from demolition and re-used. They are popular for heritage matching and architectural character:

BS EN 771-1:2011 requirements for reclaimed bricks:

• Reclaimed bricks used in load-bearing applications must be tested and classified under BS EN 771-1
• Testing: compressive strength, water absorption, soluble salt content, dimensions
• Bricks sold as "decorative" or "non-structural" do not require classification — but should not be used in any structural position

Practical considerations:

• Inspect for spalling, cracking, mortar residue, and freeze-thaw damage before specifying
• Reject any bricks with spalling (surface layer delamination from frost) — they will continue to fail
• Hard-to-clean mortar residue reduces the purchase value; include cleaning costs in price comparisons
• Regional brick types: London stocks, Staffordshire Blues, Leicestershire Reds, Yorkshire Sands all have distinct appearances; source locally for best match to existing

Heritage matching: For listed building repairs and conservation area work, matching the existing brick by colour, texture, and dimension is essential. A specialist reclaimed brick merchant can often match within two to three shades. For exact matches, take a sample brick to the merchant rather than describing colour.

Calcium Silicate Bricks

Calcium silicate bricks (sand-lime or flint-lime bricks, BS EN 771-2) are manufactured by autoclaving a mix of sand (or crushed flint) and lime under high pressure:

• Uniform pale cream, off-white, or grey colour
• High dimensional accuracy (very consistent sizing)
• Low water absorption; no clay-based firing process means no soluble salts
• No efflorescence risk (a significant advantage over clay bricks)
• Frost resistance equivalent to F2
• Compressive strengths from 15 to 50+ N/mm²
• No colour variation between batches (advantage for large projects)
• Lower thermal mass than clay bricks
• Less common in traditional UK residential; more popular in commercial and Scandinavian-influenced residential

Concrete Bricks

Concrete bricks (BS EN 771-3) are manufactured from dense concrete aggregate:

• Used primarily as commons in blockwork
• Available in facing grades with coloured aggregates
• Higher density than clay; 2,400 kg/m³ vs 1,800–2,000 kg/m³ for clay
• Limited aesthetic options; used where cost is the primary driver
• Colour fades over time; less durable appearance than clay
• Not used in heritage, conservation area, or high-specification work

Standard UK Brick Dimensions

Coursing: 4 courses = 300mm; 8 courses = 600mm. Use this for setting out openings and calculating brick quantities (see brick quantities).

Metric vs imperial: Many UK properties were built with imperial bricks (3" × 9" × 4½"). The slight size difference (65mm metric vs 73mm imperial with joint) means coursing does not match between old and new work. Extensions and repairs to pre-1970s buildings require careful coursing adjustment or special purpose bricks to maintain course alignment.

Frequently Asked Questions

How do I match bricks for a house extension?

Matching existing bricks is one of the most challenging aspects of extension work. Start by identifying: the brick colour and texture; the course height; and whether the brick was laid with a weathered, bucket-handle, or flush joint. Take a sample brick to a brick merchant — do not rely on written descriptions or photographs. Be prepared to source reclaimed bricks for an older property where current production does not closely match. Budget for 10–15% extra over the calculated quantity for selection/rejection of poor matches.

What is the minimum compressive strength needed for a garden wall?

For a single-skin garden wall in a non-load-bearing position, most facing bricks with 15–20 N/mm² compressive strength are adequate. The more important specification for a garden wall is frost resistance (F2 required for fully exposed conditions) and water absorption (T or M for coping bricks). The mortar specification is equally important — use a 1:1:6 cement:lime:sand mortar for flexibility; do not use a hard cement mortar on softer facing bricks.

Can I use common bricks in an exposed position if I render them?

Yes, if the render fully covers the brick and prevents water ingress. Common bricks are fine as a substrate for render (the higher porosity of commons gives good render key). However, the render system must be continuous and well maintained — any cracking allows water penetration. Use a lime-based render on historically inappropriate (pre-1930s) brickwork; cement render on modern construction. The render specification must also be frost-resistant at the finish coat level.

What does 'S0' mean on a brick data sheet?

S0 means no specific classification for soluble salt content has been stated (under the old BS EN 771-1 marking scheme). The current standard uses S1 and S2; S1 indicates higher soluble salt content acceptable only for protected positions; S2 indicates low soluble salt content suitable for external work. Bricks marked S0 should be treated cautiously for external use — request the manufacturer's test data on soluble salt content before specifying in fully exposed locations.

Regulations & Standards

• BS EN 771-1:2011+A1:2015 — fired clay masonry units; specification, performance classes, and test methods

• BS EN 1996-1 (Eurocode 6) — design of masonry structures; compressive strength requirements for load-bearing applications

• BS EN 845-1 — masonry accessories; specification for ties, tension straps, hangers and brackets

• NHBC Standards Chapter 6.1 — ground floor external masonry; brick selection requirements below DPC

• Brick Development Association — UK industry body; technical guidance on brick selection and specification

• BSI BS EN 771-1 — British Standards Institution

• NHBC Standards: Technical Zone — National House Building Council

• Ibstock Brick Technical Library — leading UK brick manufacturer technical guidance

• Historic England: Brickwork Repair — guidance on matching and repairing historic brickwork

• efflorescence — causes, treatment, and prevention of efflorescence

• expansion joints — movement joints in brickwork

• brick quantities — brick quantity calculator and coursing tables