Brick Slips: Adhesive Installation, Grouting and BS EN 771-1 Requirements

Quick Answer: Brick slips (brick tiles) must be fixed with a full-bed C2S2 adhesive (BS EN 12004 classification) for external use — spot-fixing is not acceptable. Joints should be 10mm to match standard brickwork, filled with matching pigmented mortar. Movement joints at 3m maximum on external applications, 5m internally. Slips over 18m height on insulated external walls require non-combustible backing per BS 9991 and PAS 9980 guidance.

Summary

Brick slips (sometimes called brick tiles or brick cladding) are thin sections of fired clay — typically 20–25mm thick — that replicate the face of a standard brick. They are used to clad steel-framed structures (SFS), concrete, timber frame, and render substrates with a brick appearance without the self-weight of full brickwork. Their use has grown substantially in the UK with the rise of modern methods of construction (MMC) and timber frame building.

However, brick slips are also one of the most frequently poorly installed cladding products in the UK. The consequences of incorrect installation — detachment of individual slips or entire panels — range from aesthetic failure to serious injury if slips fall from height. The Grenfell Tower fire and subsequent regulatory changes have fundamentally changed the regulatory landscape for external wall systems, and brick slips are directly affected by the requirements for non-combustible cladding above 18m.

This article covers substrate requirements, adhesive selection, joint detailing, movement joints, the fire safety requirements, and the planning implications for brick slip cladding in conservation areas.

Key Facts

Quick Reference Table

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Application Minimum Adhesive Movement Joints Fire Classification Mechanical Fixings
Internal feature wall C1 or C2 5m max Not required Not required
External below 18m C2S2 minimum 3m max EWS1 if required Recommended above 6m
External 11m–18m (multiple-occupancy) C2S2 3m max B1 or A2 backing Required
External above 18m C2S2 3m max A1 or A2 backing Required (mandatory)

Detailed Guidance

Substrate Preparation

The substrate is the foundation of a brick slip system. Failure here causes panel failure regardless of adhesive quality:

Acceptable substrates:

Substrate checks before fixing:

  1. Suction: brick slip adhesive relies on the substrate having sufficient suction to form an initial bond; pre-wet dusty or high-suction surfaces; allow to reach surface-dry condition before adhesive application
  2. Flatness: substrate must be within ±5mm in any 2m length; high spots or hollow sections telegraph through to the slip face
  3. Strength: substrates weaker than C20 concrete may need reinforcing or priming before slip application
  4. Cleanliness: oil, dust, loose material, efflorescence, and biological growth must be removed

Adhesive Selection: BS EN 12004 Classification

BS EN 12004 classifies tile and brick adhesives by:

For external brick slips: C2S2 is the minimum acceptable classification. This ensures:

Full-bed application (mandatory):

Spot-fixing is not acceptable. Spot-fixing leaves hollow areas behind slips that trap moisture, create freeze-thaw expansion risk, and reduce the bond area by 50–75%. Spot-fixed slips are a falls-from-height risk.

Joint Tooling and Grouting

Joint widths:

Joint filling methods:

Mortar gun/pointing mortar:

  1. Mix pointing mortar (cement : sand 1:4 with plasticiser, plus pigment to match brick colour)
  2. Apply with a pointing gun or pointing trowel; fill joint completely with no voids
  3. Tool with a jointing iron when mortar has reached firm but not hard consistency (thumb-print hard)
  4. Match the joint profile to the existing brickwork: bucket-handle, flush, or weathered as specified

Pre-mixed sanded grout:

  1. Polymer-modified sanded grout (BS EN 13888 class CG2WA); available in brick-matched colours
  2. Applied by rubber float or pointing tool; joints packed fully
  3. Wipe excess from slip face with a damp sponge before grout hardens

Pigmented polymer pointing compound:

  1. Single-component pre-mixed product (e.g. Parex, Remmers Fugenmortel); coloured aggregate gives natural brick mortar appearance
  2. Applied by mortar gun; tooled to match specification
  3. Slower cure than cementitious mortar; better stain resistance

Movement Joints

Movement joints in brick slip systems must accommodate:

  1. Thermal movement of the slip (clay brick: 6 × 10⁻⁶ per °C)
  2. Differential movement between slip and substrate (particularly on SFS where the steel frame moves differently to the brick)
  3. Structural movement joints in the backing structure

Movement joint spacing:

Movement joint detailing:

Fire Safety and Height Requirements

The Grenfell Tower fire in 2017 led to a fundamental review of external wall systems and combustibility. The key changes affecting brick slip systems:

Buildings above 18m (approximately 6 storeys) — residential:

PAS 9980 (External Wall Assessment):

Mechanical fixings above 18m:

Conservation Area and Listed Building Considerations

Brick slips on buildings in conservation areas or on listed buildings require careful consideration:

Frequently Asked Questions

Are brick slips as durable as real bricks?

A correctly installed and jointed brick slip on a properly prepared substrate can achieve a service life equivalent to full brickwork — 50+ years. The failure modes are different: full brickwork fails by frost damage, mortar decay, and movement cracking; brick slips fail primarily through adhesive bond failure (detachment) if incorrectly installed. With correct installation — full-bed C2S2 adhesive, movement joints at 3m, mechanical fixings above 6m — brick slips are a durable cladding system.

Can brick slips be installed on a timber-framed house?

Yes, with a suitable substrate. A cement particle board or glass reinforced cement (GRC) board mechanically fixed to the timber frame provides a stable, non-combustible backing. The timber frame must be clad in a breathable breather membrane with a minimum 20mm drained cavity between the membrane and the backing board. This ventilated cavity manages any moisture that penetrates the brick slip layer. Direct application of brick slips to OSB or plywood is not recommended for external use.

What is the difference between C2S2 and C2TE adhesive?

C2TE is cement-based, enhanced (C2), with the T designation (tile adhesive — reduced slip for vertical surfaces), and E designation (extended open time — allows repositioning the slip before the adhesive skins). C2TE does not include the S2 deformability classification. For external brick slips where differential movement between slip and substrate is a concern, C2S2 is the correct choice. C2TE is more appropriate for dry internal tile work where open time is more important than deformability.

How do I handle the corners of brick slip panels?

Corner detailing is one of the most challenging aspects of brick slip installation. Options:

  1. Return slips: purpose-made corner slips with a 90° return (L-shaped cross section) that replicate a brick corner; most authentic appearance
  2. Mitre: two slips mitre-cut at 45° to form the corner; requires precision cutting and careful grouting
  3. Corner bead: metal or PVC corner bead defines the arris; slips butt against it on each face; less authentic but simpler

Return (L-shaped) corner slips are the professional standard for conservation area work. Mitre joints tend to open with thermal movement, allowing water ingress at the corner.

Regulations & Standards