Brick slips are thin sections of real or reconstituted brick — typically 20–25 mm deep, 215 mm long, and 65 mm tall — applied to a substrate to give the visual appearance of a full brick wall. They are used where a structural brick outer leaf is impractical: on timber-frame buildings, over external wall insulation (EWI), on steel-frame commercial construction, or in refurbishment where the existing façade is retained but re-faced.
Brick slips look identical to full brickwork when well laid and pointed. The distinction only matters to engineers and surveyors, not neighbours. However the two systems differ substantially in cost, longevity, risk profile, and suitability for different substrates.
Brick Slips vs Full Brick Outer Leaf
| Factor | Brick slips | Full brick outer leaf |
|---|---|---|
| Depth added to wall | 25–35 mm | 102 mm + 50 mm cavity |
| Weight on structure | ~45–60 kg/m² | ~200 kg/m² |
| Lifespan | 25–50+ years (adhesive dependent) | 100+ years |
| Risk of failure | Delamination possible if adhesive fails | Very low once built |
| Cost installed | £60–£120/m² | £80–£140/m² |
| Planning appearance | Identical | Identical |
| Cavity ventilation | Not required (if on EWI) | Required — 50 mm min |
Full brick is always the more durable option where the structure and budget allow. Brick slips are a pragmatic compromise where load or thickness constraints rule out the traditional approach — common on modern timber-frame houses, modular construction, and retrofits where the floor loadings cannot accept a heavy outer leaf.
Fixing Methods
Adhesive-Only Systems
The most common approach for residential work. A cementitious or epoxy-based adhesive is applied to the substrate and the slip is pressed into position, then grouted with proprietary mortar matching the slip colour. Adhesive systems are faster to install and cost less, but depend entirely on bond integrity over time.
Adhesive brick slips require:
- A flat, stable substrate — no more than ±3 mm over 3 m
- A substrate that will not deflect or expand independently of the slip (EWI boards must be firmly bonded and at least 80 mm thick EPS/PIR)
- Thermal movement joints at max 6 m centres horizontally and at every floor level vertically
Products must carry a BBA Certificate or equivalent UKCA marking for external use in UK exposure conditions.
Mechanically Fixed Systems
Stainless steel rail-and-clip systems, where individual slips hook onto horizontal carrier rails fixed back to the structural substrate. These are standard on:
- Buildings over 11 m (required where the fire classification of adhesive is in doubt)
- High exposure zones (SW England, Wales, Scotland — BS 8104 zones 3–4)
- Refurbishment where substrate quality is uncertain
Mechanical systems cost 20–35% more than adhesive but are preferred by structural engineers and building control on any building where delamination failure would be a safety risk. The slips themselves are thicker — typically 25–40 mm — and purpose-extruded or cut with a groove to accept the clip.
Application on EWI Systems
Applying brick slips over EWI (external wall insulation) is increasingly standard on new-build affordable housing and whole-house retrofits. The EWI board — usually EPS, mineral wool, or PIR at 90–150 mm — is first fixed to the structural wall in the normal way. A reinforcement mesh and basecoat are applied to stabilise the EWI surface. Brick slips are then fixed through the insulation into the structural substrate using mechanical fixings or onto the EWI surface using adhesive.
The performance benefit: the continuous insulation eliminates cold bridges through mortar joints and timber studs. U-values of 0.15–0.18 W/m²K are achievable with 100 mm EPS EWI before brick slips are applied.
Building Regulations (Approved Document L, England 2021 and 2025 amendment) require the overall U-value of the external wall to be declared for SAP calculations — brick slips themselves add minimal insulation (lambda ~0.9 W/mK) but their substrate system is where thermal performance is achieved.
Application on Timber Frame
Timber-frame outer walls (structural insulated panel or light-gauge steel frame) cannot carry the weight of a traditional brick outer leaf on most domestic spans. Brick slips on a racked sheathing board — typically 18 mm OSB or structural ply — allow the masonry appearance without the structural load. The sheathing must be restrained against suction and positive wind pressure to Eurocode 5 (BS EN 1995-1-1) calculations.
A ventilated cavity of at least 25 mm is typically included between the sheathing and the slip substrate, with breather membrane on the sheathing face, to comply with Approved Document C (weather resistance).
Cost Breakdown
| Element | Approximate cost |
|---|---|
| Brick slips (standard stock, adhesive type) | £18–£35/m² supply only |
| Brick slips (special colours or sizes) | £35–£65/m² supply only |
| Adhesive installation (labour + materials) | £40–£60/m² |
| Mechanical rail system (supply + install) | £65–£90/m² |
| Pointing and clean-down | Included in above |
| Movement joints and sealant | £8–£15/lm |
Prices are 2025–2026 UK mainland averages. Scottish islands, remote rural areas, and London add 10–25% to labour rates. Scaffold, access, and fire cavity barriers are additional.
Planning and Conservation Considerations
In conservation areas and on listed buildings, planners often require that external materials match or complement the existing brick type. Brick slips generally satisfy this requirement provided the colour, texture, and bond pattern match the surrounding townscape. A sample panel for planning officer approval is good practice before committing to large-scale purchase.
Standard applications on new-build outside conservation areas or Green Belt do not require specific planning permission for the cladding material choice — it is determined by full planning consent for the building’s external appearance.
Key Standards and Guidance
- BS EN 771-1 — specification for clay masonry units (covers the parent bricks from which slips are cut)
- BS 8000-3 — workmanship on building sites, masonry (mortar and jointing)
- BBA Certificates — required for adhesive brick slip systems used as primary weather defence
- Approved Document B — on buildings ≥11 m, the fire performance of the complete cladding assembly including adhesives must be assessed; mechanical systems are the safer default
- Approved Document C — wall must resist driving rain; slips plus appropriate basecoat and waterproof render satisfy this if jointing is continuous and movement joints are provided
- NHBC Chapter 6.9 — technical requirements for cladding on NHBC warranty schemes
Always use a contractor with demonstrable experience in brick slip installation and check that the slip product selected has test data for the specific substrate and exposure zone you are working in.
