Both timber and steel are used in roofs. Each material has advantages and disadvantages.
Supporters of steel roofs (which are being used nowadays by a number of major builders) argue that it is more environmentally friendly, fire safe and termite proof.
However the timber industry rejects these arguments, stressing the high level of embodied energy use in steel roof manufacture, and the fallacy of the fire and termite arguments. Proponents of timber argue that the use of plantation pine is a renewable resource and that there are various effective termite prevention methods available in the market place.
Even the current concerns about the European House Borer may be a non-issue with the use of treated pine. New products are promoted as effective against infestation.
There is an ongoing debate over the relative strength of steel versus wood. Timber is of course lighter than steel and is easily worked with.
From a builders point of view, steel provides an opportunity for wider ceiling spans (which is important with the popularity of open areas in new homes), straighter ceilings and screw based rather than nail fixing. Steel roofs are prefabricated rather than constructed on-site which perhaps reduces the chances of human error. Such a “supply and fix” arrangement frees the builder from supervising the work of on-site roof carpenters.
Some people argue that steel roofs are much noisier due to expansion and contraction as the air temperature rises and falls. However owners of steel roof houses report that their houses are “whisper quiet”.
With the cost of steel increasing significantly over recent times, timber has become more popular with many builders again.