Roofing expands and contracts due to temperature changes in the cladding, and particularly rapid changes can be caused by passing clouds or a strong breeze. For example: if a passing cloud suddenly shades the roof from the sun, the cladding temperature could drop about 3°C after 30 seconds in shade and about 10°C after 2 minutes in shade.
Thermally induced noise is caused by slipping at fasteners/connections where the roof expands relative to its supports/clips.
The slipping is controlled by the friction between the roof and its supports/clips. When the static friction is overcome impulsively, sounds are produced – the higher the friction, the louder the sound. No damage to the cladding or fasteners will occur. The sounds produced can be variable from crackling noises, banging noises, clicking noise to loud pistol shots, and the patterns and continuity of the sounds can vary.
The noise can be reduced by a range of methods, depending upon the type of roofing. As a guide some of methods may include:
- Placing a material with low coefficient of friction between the roofing and its supports (for example PVC tape or strips of foil laminate);
- Choosing steel supports rather than timber (lower coefficient of friction);
- Choosing light coloured roofing;
- Venting the roof space;
- Including an expansion joint being careful about design details in valleys (where heat tends to be retained);
- Insulating the roof space to reduce the thermal differential.
- In tropical areas it may be better to insulate the ceiling rather than the roofing (which can also reduce noise) by having the silver foil facing upwards towards the roofing, instead of downwards towards the ceiling;
- Insulation pulled tight enough to hold the blanket hard against the underside of the roofing to dampen the noise;
- For clip-fixed roofing the spacing of the supports should be maximised. This is particularly important for the high-performance clip-fixed roofing with preference for the support spacing to be 1500mm or greater;
Ensure that the structure is rigid and well braced to minimise movements resulting from such things such as vibrations, wind, or thermal action.