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[SEAOC] Re: [SEAOC] Re: Reroofing (Was: Basic Roof Rafter Analysis Question )

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I have a question about the reroofing process.  How often do you require the
spaced sheathing to be removed inorder to place new plywood sheathing to
create a diaphragm between the shear walls.  Is this practical and how much
more does this cost to remove the spaced sheathing?  I have heard of some
people just putting the new plywood sheathing over the existing spaced
sheathing while others omit the plywood sheathing and reuse the existing
spaced sheathing when reroofing with shingles or shake.  I know when I have
seen houses being reroofed, either they do not use plywood or simply nail the
plywood over the spaced sheathing. 

I realize that by nailing over the existing spaced sheathing there are
problems (nail congestion on spaced sheaths, gaps between spaced sheaths,
etc.), but does this cause less damage and a safer working condition (support
is provided for the compression edge of the rafter) than removing the spaced
sheathing and nailing new plywood directly to the existing rafters.  By
nailing over the existing spaced sheathing do you believe we can provide a
diaphragm that is adequate to transfer the loads.  I agree that nailing
directly to the rafters would be the best soultion, but is it the most

Michael Cochran S.E.
Brian L. Cochran Associates
Los Angeles, CA

In a message dated 96-08-14 12:16:54 EDT, you write:

<< Subj:	[SEAOC] Re: Reroofing (Was: Basic Roof Rafter Analysis Question )
 Date:	96-08-14 12:16:54 EDT
 From:	eqretrodr(--nospam--at) (Steve Privett)
 Reply-to:	seaoc(--nospam--at)
 To:	seaoc(--nospam--at)
 One point I forgot in the issue of re-roofing is 
 that I recommend that Simpson a35s (or equal) be 
 installed around the perimeter of the diaphragm to 
 the wall below..  If the existing roofing is being 
 removed and the spaced sheathing being replaced 
 with ply, (as required when the move to tile is 
 made) It's easy to do and improves the existing 
 connection (if one even exists).
 Steve Privett CE