Here is why that is not the best idea (the best idea is to take the spaced sheathing off and install the OSB/plywood directly on the rafters):
So...I went looking for professional opinions on this: After searching a roofing forum and visiting 20 or so web-sites, I cannot find a single place where it suggests removing the skip sheathing is the preferred method. The opinions on the forum vary from "it's not necessary" to "you'll have a structurally stronger roof with the skip sheathing left in place". Nowhere on the form could I find a recommendation to remove the skip sheathing.
The other various web-sites include a number of city guidelines demonstrating the proper nailing methods to apply OSB or ply over the skip sheathing. None of those suggest the preferred method would be to remove it. In fact Robert's own call to his local AHJ resulted in "I called the local county code office and roof requires a tear-off to wood slats".
- The OSB or plywood would not be supported entirely along their ends, unless ... you went to the trouble to cut strips of the same thickness as the spaced sheathing and securely nailed those strips to the top of the rafters.
Agreed, but the gaps aren't that large and with 2 nails minimum per slat my gut feeling is that wouldn't be an issue.
- The nails used would have to be enough longer to compensate for the extra 3/4" or more of wood thickness of the spaced sheathing.
Of course...
any decking requires the proper nails. (see the links below for recommended nailing.)
- Even with the above being done, the structural panel sheathing will lose some of the load it is transferring to the structure (the rafters) with the nails through the spacers between the spaced sheathing and through the spaced sheathing (the sheathing now would have an indirect connection to the rafters).
I don't believe that trapping a piece of solid wood between the decking and the rafters (with the right nails) would result in a weaker connection. And...no one is suggesting you nail in the areas with the spaces directly below.
Jerry, I don't know how often you would see a skip-sheathing roof re-decked down there, and your local codes may be different in hurricane country. Up here in the Great Top-Left, the vast majority of older homes had wood shingle roofs and many "newer" homes had shake roofs. I can't tell you that the skip sheathing is never, ever removed as I'm not able to always determine the original, but I do know that I see it left in place a LOT, both on the homes I inspect and just walking or driving by ongoing re-roofs! The one thing I definitley can say is that OSB (or ply) over skip feels a damn sight more solid underfoot than "new" homes without it. I recently had about half of my own, 1927, roof stripped and re-done as part of a remodel (the rest was new) and now have ply over the skip in those areas. I'm very comfortable with the results.
I guess, ultimately, Robert should discuss it with his roofer.
A couple of city examples...
http://www.ci.clovis.ca.us/UMAP/User...ofing-Plan.pdf
http://www.ci.pittsburg.ca.us/NR/rdo...ngbulletin.pdf