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Bob Mariani 07-12-2009 08:24 AM

creating a cathedral ceiling
Trying to get ideas on what I need to assure building integrity with this project. I have a low slope roof over a family room which is over the garage. The ceiling is low, so I intend to remove the ceiling joists to create a cathedral ceiling. But the rafters are only 2X6. 16" OC. Span of the room is 12' I thought joist hangers could be used to avoid the outer wall from bowing, but it seems I may have more issues since the roof rafters were only 2X6. And the ceiling joists that I am removing are 2X10?? This roof ends into the second floor wall, so no ridge is involved. But no venting of existing roof is present either. Any ideas on how to deal with this one?

SNC 07-12-2009 11:36 AM

you say the roof ends into a wall, does that mean you have a shed type roof on that room or are ther rafters sloping in both directions like a gable roof ?

Bob Mariani 07-12-2009 12:49 PM

shed roof

Gary in WA 07-12-2009 01:57 PM

Here: Low slope, ceiling supported, doug-fir #2--- 12'3" span. Any snow load?

Did you check your local B.D. for their web site? Most cities list everything pertinent.

There is a (should be) ledger attached to the studs and hopefully fire-blocked. Local code would say shear hangers required or not (I would). Definitely add positive tie at rafters to exterior wall for spreading. H-1's, H-2.5's, as per B.D.

Venting rafters is required by adding 2x? to archive thickness required for insulation value as per locale. Replace/drill rafter blocks at ext. wall, add screening. Or add closed soffit with screened continuous venting, easier? Add styro. foam insul. breathers.

Questions? Be safe, G

Bob Mariani 07-12-2009 04:42 PM

blocking at the wall connection is there. Venting is not, but no way to vent. No overhang at all. and the shed roof terminates into the second floor gable end wall. I know it should be vented, but seems to be no way and it was not vented for the last 50 years and none of the roof sheathing was damaged nor were any of the rafters. The task is to raise the ceiling as much as possible. Only going up on the high point 24", not much of a change. just could not understand why they added a triple 2X10 in the center ceiling joists.

Gary in WA 07-12-2009 06:57 PM

Were the 2x10's for the ceiling joists to come off of or were the 2x10's running with the rafters? Where were they in relation to the room? Center, on one end? Must have been a purpose..... If a permit is used, you may have to vent. They also make a wall vent for the top. Be safe, G

Scuba_Dave 07-12-2009 07:09 PM

Shed roof cans be vented
I vented my sunroom cathedral ceiling which is a shed roof

Bob Mariani 07-13-2009 05:10 AM

The 2X10's were used as ceiling joists. These are what I am removing. This whole question came up while trying to figure out why they are used to start with. Some of the ceiling joists are 2X8, some 2X10 and one triple 2X10. Possibly overkill to support the skylights.

Gary in WA 07-13-2009 12:21 PM

Some framers/DIY'ers would use 3-2x? in the middle of a long span then branch a grid from there with lesser strength wood to save money. At right angle to the 2x? This is why the odd question of placement. I'm betting they ordered too many floor joists and used the extra here. In demo, I've seen ceiling joists with concrete on them from the footing pour. Skylights make a little more sense, if the bigger ones were carrying members. Or possibly when framing, the carpenter said "we are out of 2x6 for the roof". Boss said "WE have plenty of 2x4's, just put a triple ceiling joist to hold up the center of the purlin for the roof". Then they found the 2x6's under a tarp. (It was wet that month). Or, the new owner had the builder install them for his home-made porch swing by his dad from the old house.

If you don't vent, use a good vapor blocking paint on the ceiling. Against mold from moisture, but you know that, I've read your posts.
Final answer: I don't know. Be safe, G

SNC 07-13-2009 08:02 PM

yep sounds like the 2x10 may have been extras
you dont have to take out the ceiling, you could just raise it up a foot or two, add some framing clips to the, rafter to top plate connection, like simpson (a-35) or something

Bob Mariani 07-14-2009 06:52 AM

Tied the rafters at both ends with hangers, only 8' opening. Using closed cell spray foam to get better insulation with the 2X6 rafters. Not replacing roofing, so no way to vent. But no houses (old ones) here have venting...New England sucks when it comes to building technology. Added two steel cables for extra client comfort level.

Scuba_Dave 07-14-2009 07:01 AM

I had one ceiling in an apt that they had the cross framing - the old ceiling joists - boxed in to look like beams
Most had been removed - I think they were 3-4' apart
It looked very nice

Bob Mariani 07-14-2009 09:31 AM


Originally Posted by Scuba_Dave (Post 301610)
I had one ceiling in an apt that they had the cross framing - the old ceiling joists - boxed in to look like beams
Most had been removed - I think they were 3-4' apart
It looked very nice

Issue was I needed to replace the leaking skylights. And also client is tall and she wants a higher ceiling. But I could see no reason for the 2X10 ceiling joists when using 2X6 rafters. Took them all out, sheetrocked, new skylights on custom raised curbs , and a new roof Tecos on all rafters both side. Spray foam insulation. Took three days two men. But would not spend the money for the correct venting, since the entire house and all houses in this area do not have it.

SNC 07-14-2009 06:27 PM


Originally Posted by Bob Mariani (Post 301604)
.New England sucks when it comes to building technology. .

:laughing: your noty kidding, i spent a few years in RI and thought I was in another country

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