Curtain walling and cladding

6.9.5Support and fixings

Curtain walling and cladding systems shall be securely fixed with suitably durable fixings to ensure adequate in-service performance.

The cladding system and associated fixings should be correctly located and securely fixed in accordance with the design and the manufacturer’s recommendations. Fixings and supports, including the type, size and positioning of anchors, fixing rails, frames, fixings, fasteners and bracketry, should be in accordance with the design, and:

  • accommodate specified loads
  • account for packing of brackets to achieve surface tolerance, in accordance with the manufacturer’s recommendations
  • be accurately set out
  • generally be stainless steel, suitable non-ferrous metal or appropriate plastics
  • be installed ensuring dissimilar metals are separated to avoid bimetallic corrosion
  • be installed ensuring aluminium components are separated from direct contact with cementitious surfaces.

Mechanically fixed systems should be in accordance with the manufacturer’s recommendations, and fixings should:

  • have the correct embedding, spacing and edge distances
  • be installed to the correct torque settings
  • have suitable locking nuts and washers.

Fixings should be manufactured from:

  • phosphor bronze
  • silicon bronze
  • BS EN ISO 3506 stainless steel
  • mild steel with coatings to BS EN ISO 2081, BS EN 1461, or other appropriate treatment in accordance with BS EN ISO 12944 or BS EN ISO 14713
  • BS EN 573 and BS EN 755 aluminium alloy
  • appropriate plastics
  • materials assessed in accordance with Technical Requirement R3.

Materials that comply with recognised standards and which provide equal or better performance to those above will generally be acceptable to NHBC.

Pull-out or destructive testing of anchors and fixings should:

  • comply with BS 5080
  • comply with the Construction Fixings Association Guidance Note ‘Procedure for Site Testing Construction Fixings’
  • be carried out in accordance with the design
  • carried out at a frequency agreed with NHBC.

The test report should be made available to NHBC.

Adhesive-fixed systems should be installed to a suitably prepared backing wall, providing:

  • an assessment of the backing wall is available to confirm suitability
  • it is used in accordance with the design.

Adhesive fixing of rails, frames, fixings and fasteners should:

  • only be specified where there is no suitable alternative
  • be used in accordance with the manufacturer’s recommendations.

Timber should only be used where it is:

  • easily inspected and replaced without disturbing the curtain walling system
  • treated in accordance with Chapter 3.3 ‘Timber preservation (natural solid timber)’.