2.5.1 Roof structure
2.5.1.1 Roofframing and roofing
(a) Distortion/lifting/damage Movement of the roof is commonly caused by the roof not adequately resisting wind uplift forces. Often the roofing is not adequately secured to the roof framing or the roof structure to the wall structure.
(b) Cupping Distortion of flat roof decks is caused by condensation. The condensed water can wet ceiling joists in contact with the deck, increasing the risk of fungal decay. It can also drip, damaging the ceiling below or wetting electrical cables.
(c) Widespread sagging Sagging of a pitched roof will be visible where roof coverings have dished, and ridge lines are bowed over strutting poi.. Deformation will commonly result front initial poor design; increase in roof covering loading; corrosion of fixings; long-term loading, lack of support; or timber damage.
(d) Localised sagging Sagging of the roof at the eaves is often caused by excessive cutting (birdsmouth jointing) of rafters.
(e) Localised sagging Sagging of the roof in the vicinity of services is often caused by excessive cutting and removal of framing members for the installation of services, especially plumbing vents and flues.