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Clutchcargo 08-18-2007 01:58 PM

Placing roof sheathing vertically
I'm putting the roof sheathing on my portico The size of each side is 52x65. The ridge length is 52. I was going to put the plywood up there vertically so that I could have the seam siting on a rafter.
I read someplace that roof sheathing should be placed so that the grain of the ply is perpendicular to the rafters. Should I continue to do the roof as I planned or run the ply perpendular to the rafters?

jiggyjack 08-18-2007 02:31 PM

I'm assuming you are talking inches. Always run perpendicular to your rafters.

Darylh 08-18-2007 05:19 PM

Plywood has its 2 outside grains rinning the length of the plywood. One of the resaons you run plywood in the oppisite direction is if you do not it will sag in between the rafters and we also use H clips between the rafters also to help stiffen the sheets.

troubleseeker 08-18-2007 09:51 PM

Like the other guys said, any type of sheet materials should be run perpendicular to their supports. This goes for drywall also. Many people do not believe that there could be any difference in drywall, but you can see for yourself easily. Cut a 12" piece across the 48" width of the sheet, and cut a 48" piece from a 12" rip of the sheet. Set them across anything so they are supported at the ends, and begin puting equal amounts of weight in the center of each, and compare the sag.

builderr 08-25-2007 11:14 AM

for such a small roof area, just go with a 3/4 inch plywood just the way you described, and you will have no problems....Would be different if you were talking about something over 8 ft in rafter length, but heavier plywood would deftinitely work. If doubtful, add solid blocking.

the roofing god 08-26-2007 11:21 PM

perpendicular,or add cats(wood blocks)at the ends and seams of panels for support,perpendicular is always better though

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