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Anyone retrofitted a vaulted ceiling from a truss system?


jccustom's Avatar
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02-15-07, 10:35 AM   #1  
Anyone retrofitted a vaulted ceiling from a truss system?

Anyone retrofitted a vaulted (rafter and single beam) ceiling from a standard truss system?

The goal is to do it without having to replace the entire roof. My dad (a general contractor) and I (former carpenter) have discussed the options. We think it's feasible to:
1) remove all drywall "in the way" (obviously)
2) retrofit the posts and beam
3) sister in larger rafters (2x10 or 12 +, whatever the load requires)
4) then remove the "inner" part of the truss system
5) insulate and finish

The only real problem I can think of is eliminating spread (the pressure of the rafters pushing out on the walls. Seems the posts should take care of this by holding the beam (at the center, high point) up.

Anyone else done this, or come up with a better solution?
Thanks
JC

 
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Concretemasonry's Avatar
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02-15-07, 11:21 AM   #2  
Anyone retrofitted a vaulted ceiling from a truss system?

Fortunately, you correctly identify the "spreading" problem.

Unfortunaelty, just "posts" have no horizontal strength.

You need an engineer to keep you on track.

Dick

 
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02-15-07, 11:49 AM   #3  
Thanks Dick / Concretemasonry,
You're absolutely right in the need for an engineer. Neither my Dad (the General Contractor who also has a Civil Engineering degree) or my best friend (an architect) seem to want to break out the paper, calculators, and books on this one. If I get really! serious, they might too. I'm hoping for some confirmation and/or some other ideas, that it's possible before I hire somebody. Most things I'll tackle myself, but, where structural loads are concerned it's wise to have a practicing pro do the final plan. Neither my Dad, I, or my brother (a former framer) have ever done this without tearing off the entire roof.
It'd be nice if we could draw pictures (illustrations) on here

 
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02-15-07, 06:48 PM   #4  
Unless you have an "odd" truss, the "spreading" is already addressed in the bottom chord, which is tied to the rafters at the top plates.

How are you planning to address the removal of the new rafter material at the seat cut and still accomplish full bearing?
Is it your plan to add blocking between the existing studs, cut a reverse birdsmouth and support the rafters with hangers?

Have your carring beam, support system and lateral resistance address by a civil or structural engineer

 
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02-16-07, 08:00 AM   #5  
Thanks Snoonyb,
Sound like you've done this once or twice.
First, absolutely, an engineer will be figuring the material needed for load etc, recommendation for fastening, etc.
The attachment of the new rafters to the top plate, retaining full bearing is one of the big issues I haven't figured out. I don't want to "hang" the new rafters 'cause I'd lose too much ceiling at the exterior wall.
The ideal way would be to make the seat cut, then cut off the rafter at the outside of the top plate. (Effectively, cutting the birds mouth, then cutting off the vertical "jaw".) Obviously, as you're getting at, there are several inches of the new rafter unsupported on the inside (since it's probably a 2x12), reducing load bearing back to a 2x4's. Do you have any other solutions?
Thanks
JC

 
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02-17-07, 05:28 AM   #6  
I would take the roof and the truss system off because it is exponentially simpler to install the support system with a clear and open work area.
As it is, to maintain your wall tie, support for the roof with a temporary wall before you cut the king post, then you'll need to crane the structural beam, then fit the new rafters under the existing roof system, then roll them into place, then remove the top 2' of roof on each side of the ridge to install the tie straps.

 
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02-19-07, 09:22 AM   #7  
Thanks Snoonyb,
Thats what I was trying to avoid, mainly to avoid the cost of replacing the roof. However, the more I go through the options, the more it looks like the only way I'll be able to reduce price is tear off the roof and reuse the sheathing. I hate the idea of that, though. I'm of the school, while you've got it torn apart, replace anything that may have some rot or could be updated (framing, mechanical, etc.)
If I had to replace the roof, I'd have to up the budget, but at least I could put on the metal that I want then, rather than when the current roof is done for.
Thank you for considering the situation and options and coming back with knowledgeable, technical advice. I'll take your's anytime.
JC

 
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