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-   -   Cutting roof sheathing at an angle (plumb) (http://www.diychatroom.com/f19/cutting-roof-sheathing-angle-plumb-68100/)

cellophane 04-01-2010 02:41 PM

Cutting roof sheathing at an angle (plumb)
 
I was working with the good folks at Habitat over the weekend and was installing a roof on a shed. We got the plywood up and in place and then ripped it flush with the end beams on the shed. Needless to say the cuts were rough at best.

Is there a technique or method to get a nice plumb cut on plywood once it is installed on a roof without having to go over it several times or having a wavy cut?

I ask for one because I'm curious, and second because I have some upcoming plywood on roof cuts at my house and would like them to end up as nice as I can get them.

kwikfishron 04-01-2010 05:51 PM

Snap a chalk line.

jlhaslip 04-01-2010 08:39 PM

Router with a flush trim bit.

troubleseeker 04-01-2010 10:53 PM

Quote:

Originally Posted by kwikfishron (Post 422830)
Snap a chalk line.

Sounds like there is no drip edge, so a freehand cut, even with a chalkline is going to be pretty wavy. The only way for a truly straight cut is to tack a straight edge in place for the saw base to follow. You still have to be vigilant about holding the base tight to the straight edge, as the slanted roof lets it drift off very easily, but fortunately it will always result in a "fat" spot, which can be cut down.

Can't envision how the suggestion of a flush trim router bit could accomplish anything in this situation:
1. It is going to cut square with the plywood surface it rides on, not
plumb.
2. There is nothing for the bearing to follow; sounds like open rafter
tails.
3. You could attach a "wedge" to the sub base to give you a
plumb cut, but that would require a very long , unprotected
exposure of bit; a very dangerious situation.

cellophane 04-02-2010 10:32 AM

Quote:

Originally Posted by troubleseeker (Post 422985)
Sounds like there is no drip edge, so a freehand cut, even with a chalkline is going to be pretty wavy. The only way for a truly straight cut is to tack a straight edge in place for the saw base to follow. You still have to be vigilant about holding the base tight to the straight edge, as the slanted roof lets it drift off very easily, but fortunately it will always result in a "fat" spot, which can be cut down.

i thought it was something simple like that. thanks :thumbup: we did snap a line but running a saw on an angle while on a ladder isnt the easiest thing in the world to do unless you do it a lot - which i don't. ;)

Willie T 04-02-2010 11:39 AM

2 Attachment(s)
Actually, you need not worry about the cut being all that straight nor perfect... as long as it is not sticking out past the sub fascia, the facia, and the drip edge. The metal roof edging is going to cover that entire cut and it will never be seen again. And I cannot imagine a Habitat structure NOT being done with a fascia and drip edge. They build a pretty economical house, but they usually try to do it right.

You should not be laying nor cutting off any plywood until at least the sub fascia (and usually fascia and drip edge too) is in place. The plywood attaches to those pieces of lumber and helps to shed off the rain and snow melt so the pieces under the plywood won't get soaked.

jogr 04-02-2010 01:02 PM

I don't understand why that edge needed to be cut on the roof at all. It should have been placed in the right position from the get-go. Doesn't everyone sheet roofs from the bottom and go up from there? If less than a full sheet was needed to start (so you don't have a narrow strip at the peak) then it should have been ripped on the ground and then placed in the right spot.

troubleseeker 04-03-2010 08:02 PM

Quote:

Originally Posted by Willie T (Post 423115)
Actually, you need not worry about the cut being all that straight nor perfect... as long as it is not sticking out past the sub fascia, the facia, and the drip edge. The metal roof edging is going to cover that entire cut and it will never be seen again. And I cannot imagine a Habitat structure NOT being done with a fascia and drip edge. They build a pretty economical house, but they usually try to do it right.

You should not be laying nor cutting off any plywood until at least the sub fascia (and usually fascia and drip edge too) is in place. The plywood attaches to those pieces of lumber and helps to shed off the rain and snow melt so the pieces under the plywood won't get soaked.

From the situation he describes, and it being a garage, sounded to me like there was open rafter tails, without soffit or facia. If here is, your take is correct, the cut is insignificant, as it will be covered by the drip edge.

cellophane 04-03-2010 09:50 PM

Quote:

Originally Posted by troubleseeker (Post 423718)
From the situation he describes, and it being a garage, sounded to me like there was open rafter tails, without soffit or facia. If here is, your take is correct, the cut is insignificant, as it will be covered by the drip edge.

the drawing willie posted is pretty close to the construction, except without the smaller soffit piece. the whole thing would have been covered by a drip edge but i was more curious how to make a nice cut along that angled edge without having the cut wander all over the place or eating into the 2xW pieces. more hypothetical than anything ;) gotta learn something new everyday!

Joe Carola 04-03-2010 10:10 PM

Quote:

Originally Posted by cellophane (Post 423090)
i thought it was something simple like that. thanks :thumbup: we did snap a line but running a saw on an angle while on a ladder isnt the easiest thing in the world to do unless you do it a lot - which i don't. ;)

Why are you cutting sheats from a ladder and not cutting on the ground and passing up the correct size sheat and correct angle?


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