I am adding an attached garage to my house and will be tying into the
existing roof. I think I have the framing figured out (hip roof). My
question is the about the roof sheathing. The existing roof is
sheathed with 3/4" 1 x 6 planks. If I used 1/2" plywood would the
1/4" difference show when the shingles are applied? I'm reroof the
whole roof. Would 3/4" plywood or 23/32 tongue and groove OSB be a
better choice? Would the thicker material add significantly to the
dead load (10 psf)? My rafter span is very close to the limit for a
2x6 without purlins. Since there are no load bearing walls in the
garage, I can't use purlins. Any comments will be appreciated.
On Jul 31, 9:22 am, firstname.lastname@example.org wrote:
What kind of shingles are you applying? Something like a 40 year
Timberline will cover a lot of sins as we say. At any rate, why use
1/2" plywood? Most roofs are sheathed with 5/8's. 3/4 plywood or OSB
would be better yet, though it would be heavy to use on a roof.
where I am all sheathing is half inch
osb on the walls
plywood on the roof
some people use osb on the roof too but i dont like it
all you have to do is get the first 2 rafters right and the ridge beam
watch how you cut the birds mouth where it sits on the top plate of the wall
when it all lines up
just duplicate it
Yes, this method will work for you. What counts is the dimension from the
birdsmouth cut to the top of the rafter. Make a template from your existing
rafter and allow another 1/4" height to make up for the difference in the deck
On Aug 1, 8:50 am, snipped-for-privacy@SPAMwowway.com (DT) wrote:
Thanks all for the responses. I will build the framing up 1/4"
assuming I use 1/2" plywood. I am also considering using 5/8" rated
sheathing and if I go that route I will build the framing up 1/8".
The existing roof uses 2x6 rafters with purlins. The span of the
garage I'm building is borderline for 2x6 rafters at 16" o.c. and
since I don't have any load bearing walls in the garage I can't use
purlins. I thinking 5/8" rated sheating for 16" o.c. and 1/2" plywood
for 12" o.c.
What do you mean I'm guessing? The span is 14' - 6". According to
the span tables for 20 lb live load and 10 lb dead load, a 2 x 6 span
is 14' 1" for 240 deflection and 14' 4" for 180 deflection. (douglas
Using thicker sheathing won't allow you increase the joist spacing.
The sheathing's job is (among other things) to distribute the load to
the joists. So the (minimum) sheathing thickness required depends on
the joist spacing. The load those joists have to carry is pretty much
independent of the sheathing, as the extra dead load from thicker
sheathing is negligible.
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