Profiled metal roofing buckling or twisting

Cause

Inadequate allowance for thermal movement at fixings – this occurs more commonly with dark coloured and aluminium roofs

Repair

  • if the roofing was installed in recent years, call the original installer back to make repairs – poor installation may lead to weathertightness problems or impact roofing durability
  • if the installer is no longer available, ask the supplier or manufacturer of the roofing material (if known) for advice. Many publish installation guidance on their websites
  • the Acceptable Solution E2/AS1 covers profiled metal roof cladding in section 8.4. Fixing requirements are given in 8.4.8.1 and Figure 39. There should be an oversized hole in the crest where required to allow for expansion, and a profiled washer and EPDM washer where required to allow for expansion
  • the NZ Metal Roofing Manufacturers’ Installation Guide for Metal Longrun Roofing and Cladding (version 1.0 May 2022) says: “Screws fitted with profiled washers to allow for thermal expansion must be installed centrally through a 9 mm diameter pre-drilled hole in the roof sheeting.”
  • profiled metal roofing manufacturers give similar advice. One manufacturer states that with darker colours and long spans, the expansion may be as much as 8.0 mm for a 10 metre sheet
  • while sunscreen gives important protection while working on a roof, do not use sunscreen containing titanium dioxide or zinc oxide. These substances can cause irreparable damage to some factory finished roofing surfaces
  • always tell someone else when you plan to work on a roof and take the appropriate safety precautions. You can find details here