6.1 External masonry walls

Also see:

3.36.26.9

6.1.16 Cladding

Cladding shall satisfactorily resist the passage of moisture and be of the quality, type and dimensions required by the design. Issues to be taken into account include:

  1. masonry cladding to framed structures
  2. joints
  3. materials for cladding
  4. vertical tile or slate cladding
  5. stone veneer cladding.

This clause is for low rise applications where the masonry is used directly for weather tightness or used in conjunction with other vertical cladding for weather tightness. Chapter 6.9 covers curtain walling and other structural cladding.

Refer to the Robust Details Handbook to check compatibility of lightweight external treatments.

  • flexible movement joints should be provided at the underside of each horizontal support member
  • the masonry outer leaf should have a minimum two-thirds of its width supported securely by the concrete frame or a metal angle. See diagram (water exclusion detail not included for clarity)
  • vertical movement joints should be provided at corners
  • the inner leaf should be adequately tied to the structural frame.

Where external claddings such as fibre cement, timber or tile hanging are installed on masonry walls, cavity barriers should be provided:

  • at the edges of cavities including eaves and verges, around openings such as windows and doors and entry/exit points
  • at the junction between an external cavity wall and every compartment floor and compartment wall.

Masonry cladding to framed structures#

Allowance should be made for differential movement between cladding and the frame. The following precautions should be taken to prevent buckling and fracturing of masonry panels:

  • flexible movement joints should be provided at the underside of each horizontal support member
  • the masonry outer leaf should have a minimum two-thirds of its width supported securely by the concrete frame or a metal angle. See diagram (water exclusion detail not included for clarity)
  • appropriately detailed horizontal joint to be provided which can accommodate all movements anticipated at the joint including deflection of substrate and the angle support system, as well as the limited compressibility of both the joint fillers & sealant 
  • additionally, horizontal movement joints should be capable of accommodating at least 1mm movement per continuous meter of vertical clay masonry 
  • vertical movement joints should be provided at corners, where appropriate
  • the inner leaf should be adequately tied to the structural frame.

Joints#

Joints between claddings and adjacent materials should:

  • be detailed to be watertight under the particular exposure conditions of the site
  • have provision for differential movement, where necessary.

Materials for cladding#

Table 7: Materials for cladding

ComponentRequirementNotes
Tiles and slatesBS EN 1304, BS EN 490, BS EN 12326-1Clay tiles for tile hanging, concrete tiles for tile hanging, slates for vertical slating
Timber boardingBS EN 942Timber should:
• comply with, and be at least J50
• be a naturally durable species or pretreated with preservative
BattensBattens should be:
• of the size specified in the design
• pretreated with preservative
Proprietary cladding systems Technical Requirement R3 Satisfactory assessment by an appropriate independent technical approvals authority accepted by NHBC

Timber cladding should be in accordance with Chapter 3.3 ‘Timber preservation (natural solid timber)’.

Prefabricated lightweight brick clad arches#

Prefabricated lightweight brick clad arches comprising cement particle or fibre cement boards, injected polyurethane core, clay fired brick slips attached with epoxy adhesive for use a decorative non-loadbearing arch above openings in masonry cavity walls should:

  • hold a satisfactory assessment by an appropriate technical approval’s authority acceptable to NHBC
  • be supported by a loadbearing lintel
  • be installed in accordance with manufacturer’s instructions
  • include a cavity tray over all openings (where manufacturer’s recommendations require cavity tray to be located over prefabricated lightweight arches, a lintel with suitable profile and durability and proprietary stop-ends and weepholes should be provided).

Vertical tile or slate cladding#

Vertical tile or slate cladding to walls should:

  • conform with Chapter 6.9 ‘Curtain walling and cladding’
  • be fixed in accordance with manufacturer's recommendations.

Stone veneer cladding systems#

Stone veneer cladding systems should be in accordance with:

  • BS 8298 when mechanically fixed
  • technical Requirement R3 when adhesive fixed
  • Chapter 6.9 when used as a brick slip/rainscreen system.

Last updated: 2nd January 2024

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