Roof sheathing is a layer of plywood, wafer board or wood planks which is nailed on the rafters and stands between them and the shingles that finish the roofing. Roof sheathing is usually made of staggered panels or boards, which can have spaces between them (open sheathing) or lie next to each other (closed sheathing). It can cover both lighter flat roofs and heavier pitched constructions. In North America, roof sheathing is manufactured from several widespread tree species, such as redwood, hemlock, fir and spruce, and can vary in thickness from a fraction of an inch to three, four and even five inches. If you are planning to build a house or remodel your current one, there are several very important reasons why you should consider installing roof sheathing.
Decrease Roof Leakage
Years ago, roofs were made only of shingles or planks, and for this reason, they would be the cause of many attic and garret inundations. Fortunately, someone came up with the idea to underlay the shingles with plywood panels, which greatly decreased, if not stopped completely, rooftop leakages caused by the elements.
Support of External Roofing Materials
Modern roofs are often covered with felts, asphalt tiles or metal shingles. These are usually small in size and need a broader base on which they can be nailed, glued or otherwise attached. This is where roof sheathing comes in, providing an excellent foundation for the support of these materials. Remember: the heavier the shingles are, the sturdier the sheathing should be.
Even Distribution of Live Loads
Besides the dead weight of the tiles or shingles, roofs often have to carry the live load of accumulated snow, tree branches or some other debris. If there is no underlying structure to bear and transfer this load, it can become too heavy in some part of the roof and make it sag or even break down. This is why having roof sheathing is so important. It can take the loads which external materials exert on the roof structure and distribute them among the joists and rafters, thus decreasing these materials’ harmful impact and providing extra resilience and better protection for the affected areas.
Partial Protection against Fire
In the past, it was a common practice to treat roof sheathing with different types of fire retardants which would slow down the spreading of the flames in case a fire broke out. Indeed, it seems only too reasonable to apply such substances to the sheathing, given that most external roofing materials (felt, asphalt, wooden shingles, etc.) are highly combustible. However, keep in mind that according to some recent studies, fire retardants may cause plywood panels to split apart and significantly decrease their stability and endurance.
Decrease Electricity Costs and Protect Environment Protection
A radiant barrier is basically a layer of aluminum that is attached to the roof sheathing of a house and fends off the sun rays and the thermal heat they produce, preventing them from overheating the attic and upper stories, so the radiant barrier can reduce the cooling bills of a household and contribute to the preservation of the environment by decreasing the use of Freon-emitting air conditioners. Since a radiant barrier is most efficient when fixed to the roof sheathing, it can be considered one more reason to outfit your roof with this valuable protective structure.