Walls and Ceilings - drywall ceiling attatched to foam board?

We are planning on opening up our bedroom ceiling and turning it into a "cathedral" ceiling. The current framing is only 2x4, so there is not enough room for enough insulation. I was thinking of using fiberglass in the cavities, and covering the whole thing with som sort of foam board insulation, and then drywalling the finished side. can this be done? . juist use longer drywall screws? any ideas or feedback? thanks

If the rafters are 2x4's I doubt there is adequate framing to support the roof. 2x4 rafters use 2x4 engineered supports to help it carry the load. I assume you intend to remove these 2x's to make room for the raised ceiling :eek: not a good idea.

actually, the 2x4's have been supporting the roof since 1918, without any bowing anywhere. The roof is entirely sound, and there is no history of any roof problem, so we are not intending on re-raftering the roof. Of course if we did, we would use large enough 2x's allow a cavity for the proper r value for our climate.

If you currently have 2x4 roof rafters and some sort of rafters or joists running horizontal to hold up sheet rock, I would be very cautious and get a second opinion. What you describe does not sound right even if it still there after 118 years.

The horizontal members could do far more than you think. They could be keeping the walls from moving outward. If they (the walls) move out, they are no longer vertical and could collapse due to the vertical loading. The drywall on the walls could also crack.

The concept of using rigid foam (EXTRUDED, not expanded extruded polystyrene) is a viable insulation concept, especially for a ceiling. You actually get far more insulation than fiberglass with the same advertised R-value.

Before putting up the foam and drywall, make marks so you will be able to hit the supports. You will need to use longer screws and extensions on your ceiing electrical boxes if you have them.

Before you make any changes, get a clear local OK before you remove any part of the structure. If you have a problem, it could end up all around and on top of you!

Dick

The horizontal members could do far more than you think. They could be keeping the walls from moving outward. If they (the walls) move out, they are no longer vertical and could collapse due to the vertical loading.

Thats exactly what I was thinking as well. The ceiling joists could very well be acting like a collar tie that is keeping the wall from bowing out. If you remove the ceiling joists, it could very well be that any normal roof load could cause the rafters and wall to pull away from the rest of the home. The ceiling joists and rafters together form a triangle which gives strength to the structure. SO removing the ceiling joists could compromise everything.

This really isn't something we can give advice on without seeing, so I'd also recommend you get some advice from a local builder or inspector who can actually look at it.

Thanks for your input, folks. There is a kneewall separating our bedroom from the attic. We are hoping to move that kneewall 5 feet back into the attic, and build a new kneewall (with 2x6 so we can put more fiberglass in). The "new" part of the room will have the sloped ceiling, until it joins up with the existing lathe and plaster ceiling. We have thought about raising the exisiting ceiling up a foot or so, so there will be some bracing up there, just moved a little bit.. I guess we should go ahead and get the engineer to sign off on it! A few extra dollars to him might make for a better night's sleep during a heavy snowstorm....