Roof Sheathing ("Sheeting")
Roof sheathing is any material that is used to provide a solid surface, decking or base to which roofing material is applied to. The most common types of sheathing used nowadays are OSB (oriented strand board) and plywood. OSB is by far the most common and the most practical when considering all factors. The roof sheathing is much more than simply just a surface to attaching roofing materials to. Your sheathing keeps the rafters or trusses in proper position and plays a key role in giving your home structural integrity. Thus you can appreciate the need to make sure that it is kept in good condition.
Sheathing is Important to Roofers
As roof installers we have a vested interest in the sheathing of your roof. Our roofing materials need to be fastened to a solid base. If there are major inconsistencies such as dips or raises in the sheathing then water may not run off the roof properly and can create issues with the roofing system. It is also just dangerous for roofers to have to walk around on a roof with rotten spots underfoot. So when we see a need to replace some or all of the sheathing we will certainly let you know.
If there are rotten spots or severe warps in the roof decking material then the areas that are damaged can be taken out and replaced with solid materials. Sometimes it may be a very small area that requires repairs and other times it may be several sheets of plywood that must be taken out and replaced. Whatever the case may be, though it is not possible to be 100% accurate in estimating the damage before the roofing material is first removed, we can usually provide a pretty close estimate of the scope of damage and corresponding repairs needed. The roof can be walked and the bad areas can usually be identified as they are often very spongy when stepped on.
The picture below shows a situation where the roof was in awful condition and many sheets of plywood had to be removed. You can see how some that still needed to be taken out when this photo was taken are very warped. We knew even in advance of tearing off the old roofing that there were going to be a lot of necessary sheathing repairs; it was obvious just from the way the roof looked and felt when we walked on it.
Complete Roof Re-Sheathing
Very rarely is a roof ever so bad that it needs to be totally and completely re-sheathed. A typical instance where a roof will need all new decking is when a composition roof will be installed on a home that previously had cedar shakes or shingles installed. Most cedar shake and shingle roofs are applied over skip sheathing (perhaps using 6 inch boards spaced out with 5 inch gaps between them). To apply composition (asphalt) shingles it is necessary to have a solid base with no gaps and thus the roof needs to completely recovered with sheathing. In most cases Don's Roofing will apply OSB right over the top of the skip sheathing after the original roofing has been removed. This method maintains the structural soundness of your home (actually adds to it) as well as provides the solid base needed to install a new composition roof.
The picture below shows a roof that originally had space sheathing on in. After tearing off the original cedar shake roof we installed OSB over the existing skip sheathing. You can see the skip sheathing on a couple areas where we had not put down the OSB yet.
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