External masonry walls

6.1
Also see:
Chapter 3.3
Chapter 6.2

6.1.16Cladding

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.

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)
  • vertical movement joints should be provided at corners
  • 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 8: Materials for cladding

ComponentRequirementNotes
Tiles and slatesBS EN 1304, BS EN 490,
BS EN 12326-1		Clay 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

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

Vertical tile or slate cladding

Vertical tile or slate cladding should:

  • have each tile or slate fixed with two nails
  • be fixed using aluminium, copper or silicon bronze nails
  • be finished with an under-course and tilting batten at the bottom edges.

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.