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Built up Roof

Started by Don P, June 06, 2006, 10:27:43 PM

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Don P

We've been working on this roof recently. Its another way to cover and insulate. My dad used a very similar system in most of his houses from the mid 60's to about the mid '80's. The walls can be anything, dad's were conventional construction, we just liked big beams in the roof. It might be possible I drifted over to the dark side, I like wood everywhere  :D.

This roof has a 5.25" x 16.25"gluelam structural ridge and 4x10 dougfir rafters on 48" centers. On top of that we used Southern Yellow Pine 2x6 T&G nailed with 2 galvy ring shank 16's per bearing. The collar ties are actually more for decoration with a structural ridge. They did stiffen it up considerably as I crawled the roof before and after though.


On the top side we applied 2 layers of 2.25" foam at R14.4 ea. and 1 layer of 1.25" at R8. The perimeter has 4 rows of 2x4's built up as a foam dam. 2x4 sleepers are then attached vertically over the foam on 24" centers. We used 8" sips screws countersunk 1/2" into the sleeper, this gave 1.25" penetration into the T&G decking. The scaffold is on the balcony overlooking that greatroom.


The sleepers are then sheathed normally with 5/8 ply. The cross gable coming in from the left is conventionally framed and will "california" onto the timber roof. I'm seeing a built in bunk in the void, they have 2 boys.


Jim_Rogers

Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Max sawdust

Don,
That looks real nice.  Did you compare costs with other insulating methods?  How about cost compared to manufactured SIP's?

Building code did not require a fire barrier on the roof?  (Drywall between the T&G and foam panels.)

Max
True Timbers
Cedar Products-Log & Timber Frame Building-Milling-Positive Impact Forestscaping-Cut to Order Lumber

Don P

We didn't do a cost comparison so I'm not sure there.

For the thermal barrier, I had to go back to the codebookand read up. Long story short, I dunno. I've never had the drywall specified in a detail even when using 3/4" t&g over foam. These have often been nationally distributed plans and details, for whatever that's worth. The code references a 15 flame test  where the other face (the foam side) cannot rise more than 250*F. No inspector has ever quizzed me on any form of foam coverage. Have you run into something before?

Max sawdust

Don,
No I have not, but then again I am not a professional builder.  Some of my anal retentive home construction friends recommend it and several SIP companies I have talked too recommend drywall behind the T&G on the roof as a fire barrier. ;)

I figure it can not be a bad idea, in the case of a fire, if it burns through the roof chances of containing it are pretty slim.

Max
 
True Timbers
Cedar Products-Log & Timber Frame Building-Milling-Positive Impact Forestscaping-Cut to Order Lumber

beenthere

It will take too long for a fire to burn through the wood for the drywall beneath the 2" decking to add any additional  protection. And I think drywall is to delay a fire from penetrating into living space, like a fire in a garage, so a roof isn't in need of more protection.  The only way I see for the drywall to help is to put it over the surface of the wood, which wouldn't be too exciting. 
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

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