Building a cathedral ceiling cottage (in Northern Maine) with 10/12 pitch, no collar ties and 2 tree timber ceiling joists. Roof is 32′ long with a partition wall at 10′, leaving the remaining 22′ covered by the 2 tree timber joists (7’6″ apart) Building is 24′ x 32′.
Ridge beam is a doubled up 2″ x 12″ x 40′ (over hangs for pulley barn beam affect).
Question is: should I be concerned about roof rafters being 2″x10″x18’with a metal roof? Some have said that I should have used several LVL’s for the ridge beam but I feel that if the walls “move” out, I will cable the outside walls.
Any suggestions on venting the cathedral ceiling.
Thanks,
Chuck
Replies
A 2X12 spanning 22' is no more than a ridge board. It won't do anything to hold the roof up.
Adding cable after the rafters sag MIGHT work. But if you attach the cables to the walls, the rafters might pull loose from the walls.
All in all, I'd say you have a bad design.
Question is: should I be concerned about roof rafters being 2"x10"x18'with a metal roof?
No need to be concerned. You had a state license architect design the house (rafters). The architect had state licensed engineer check the forces that are being applied so it would be safe and meet codes and the laws of physics . You also had the building code department check the plans and made sure the plans if follow would meet code right. Then there is no need to be concerned as long as you ( DID NOT ) change the plans with out having architect and engineer check them.
If you did not it could kill you.
Is this a design that you came up with yourself or out of a book? It sounds like you might want to talk to an engineer before it gets built. Don
Chuck, at firtst thought, it is under engineered - probably so. If I understand the info correctly, this is what it looks like in section. You are relyiong on the sectional size of the timber tree logs to support the majority of the roof. I don't know what size they are, so your guess is as good as mine. The ridge has almost no value at that span of 22' in that size.
Consider this - change the ridge to a simple ridfge board since that is all it is, and add another log immediately below it for actuall strength. That way, You have three logs supporting it all. Make them in the neighborhood of 14" diameteer .
Make sure that you support them well to foundation at each end.
The rafters are fine at 2x12 as lonfg as you get edequate insulation in them. I would place a good unbroken VB immediately above the decking you use for exposed cieling and insulate with blown chopped FG or cellulose and not worry about venting, or look into structural insulated panels for the roof. It would be quick, have it's own insulation, VB, and integrity built in.
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I missed the part about cabling the outside walls. Good trick if you don't mind looking at the cable, er clothesline...
;)
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Plan on cabling/turnbuckle on top of the tree timber/ceiling joist. Won't see a thing.
(only if I need it)
Cable needs to be at top of walls to do any good
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