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-   -   Asphalt roof repacing a cedar shake roof. Technical Question (http://www.diychatroom.com/f9/asphalt-roof-repacing-cedar-shake-roof-technical-question-176600/)

artpix 04-08-2013 02:25 PM

Asphalt roof repacing a cedar shake roof. Technical Question
 
Hello,

I am getting ready to replace our 25 year old cedar roof with asphalt shingles. Some roofers plan to remove the old roof and the strapping before putting down 5/8" plywood while one roofer wants to remove the shakes, keep the strapping and attach 1/2" plywood to the strapping and then add the asphalt on top. This is less expensive but am I making a mistake going this way? The strapping seems good, no rot but I suppose it could break from more nails.

Thank you,

Dave

jagans 04-08-2013 04:18 PM

If by strapping you mean the spaced sheathing, I would not remove it if it were mine, and in good shape the reason is that the framers were not all that worried about the exact centers at 16 or 24 inches back when they did these roofs. A lot of times you will find them at 18 inches but they could vary quite a bit. It will also provide much better support. You do want to be sure that the roofer of choice checks the fastening of the spaced sheathing though and make sure it is good with 8d hot dipped galvanized nails, two per connection. I have done this many times with good success.

Windows on Wash 04-08-2013 08:16 PM

+1

Leave it and go over top with CDX plywood (exposure 1).

The skip sheathing will just make the roof that much more solid as jagans said.

jagans 04-08-2013 08:29 PM

Quote:

Originally Posted by Windows on Wash (Post 1155074)
+1

Leave it and go over top with CDX plywood (exposure 1).

The skip sheathing will just make the roof that much more solid as jagans said.


Just FYI: No CDX Eric. CD Exposure 1. Fir highly recommended.

X designation was for Exterior Glue, as they actually had interior glue prior to about 1965. Obvious problems due to framed houses that were not blacked in, and keeping dry during transportation. All plywood since the 60's has exterior glue. CD= C face Veneer D back veneer, Exposure 1 = use designation :thumbsup:

Also FYI test for delamination is to boil a 6 x 6 inch piece for 4 days :eek::eek::eek::eek: so if you have any coming apart you can bet it ain't from here. (USA)

Windows on Wash 04-08-2013 08:45 PM

I was under the impression that there will still interior glue based plywoods. Obviously stuff in the C-D range is most likely going to be specified for exterior use and therefore exterior glues.

There is a bunch of low VOC and urea/formaldehyde free wood out there now and I am not sure what these guys are using in terms of glue.

Exposure 1 is a must.

Thanks for the education..as always.


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