The type of sheathing and condition of the wood deck are important factors in determining how a new roof system should be fastened to the sheathing. Residential roof decks in the Lynchburg, Virginia areas almost always consist of wood sheathing. The most common construction types are plywood, OSB, 1" x 6" planks, and 1" x 10" planks. Newer homes usually consist of plywood or OSB roof sheathing while those built prior to 1970 may have sheathing consisting of 1" x 6" (or greater) planks. After an old roof system is removed, a roofing contractor will inspect the roof deck to determine if the sheathing is in good condition or if any of it should be replaced. Damaged wood will not be able to accept a nail driven with a hammer or a nail gun. After all damaged wood is replaced, the deck should be inspected for gaps in the sheathing that a nail could potentially be driven into (instead of solid wood). Gaps in sheathing rarely occur in plywood or OSB by and are more common in systems with plank sheathing.
Problems can occur if a nail gun is used on a house with a significant amount of gaps in the roof sheathing. If a nail from a nail gun is lodged between the planks, the shingle will not be properly fastened. It is impossible to see if a nail hits solid wood since the roof deck is covered by felt paper. Hand nail installers are quick to ‘feel’ a nail miss the wood sheathing while nail gun operators have to rely on sounds and intuition. A good contractor will inspect the roof sheathing after it is removed to determine if nail misses are likely to occur. If this is the case, hand nailing should be preferred over the use of a nail gun.
Shingles should be mechanically fastened with a pneumatic nail gun if the contractor determines that the roof sheathing is consistent and free from gaps. Most roof systems with plywood or OSB sheathing will fall into this category. Gun nailing is a more efficient and consistent installation method on these types of roof decks. Drawbacks to hand nailing in these cases include inconsistency, increased vibration on the structure, human fatigue (and the associated hazards), and interior damage.