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Framing a tray ceiling

Newpoint's picture

     Want to frame a tray ceiling in an unfinished attic. It is a gable roof with 2x6 rafters.  Not sure of the pitch of the roof but guessing 6 or 8/12 pitch.  There is a 6' high knee wall  on both sides that are approx 14' long. The length of the rafters guessing 20' or so.  Knee wall approx in the middle span of the rafters.


     Since the knee wall is only 6' high want to start the ceiling at 8'.  Currently there are some rafter/collar ties at this 8' made from 2x8's. The current span of these ties are approx 9' -10'. 


    Two questions I have are: 1) 2x8' clg rafters  necessary for a 1/2" drywall ceiling ,that will have no one walking on it only light storage? Thought of using 2x6's for the ceiling rafter with vertical hanging 2x4's mid span  near the ridge beam to the 2x6 ceiling rafter.  2) The other question was the ceiling rafters would not be resting on the knee wall but rather 2' up from the knee wall nailed  to the existing 2x6 roof rafter.  Will the roof rafter support the ceiling rafters? Thanks for any help or suggestions.


Edited 10/20/2008 11:15 pm ET by Newpoint


Edited 10/20/2008 11:19 pm ET by Newpoint

(post #107283, reply #1 of 7)

bump

 


I'm just sayin'

(post #107283, reply #2 of 7)

bump

 


 


I'm just sayin'

(post #107283, reply #3 of 7)

I'm not sure of everything that your trying to describe, but I can address a few issues.


One is that I would strip the bottom of the rafters with 2x2s so that when you install the insulation you will have enough room for ventilation. It is also a good idea to first install the styrofoam chanels to the underside of the decking.


If your rafters are 2' o.c. then I would use 5/8 sheetrock.


Also having to make a few assumptions which is always dangerous, I would assume that the rafters will hold the ceiling joist just fine. I would put some extra blocking under the ends of the joist for extra support.


I'm confused about "2x8' clg rafters  necessary for a 1/2" drywall ceiling ,that will have no one walking on it only light storage?" Are you planning on storing items on the new ceiling or are you talking about the 1st floor existing ceiling? Assuming that your talking about the new ceiling, if your joist are only going to be 9' or 10' then 2x6s should be fine.


I answered just trying to be helpful, but you really need to get someone local to look at it. Even posting pictures here would be dangerous. Finding someone who knows what they are doing and what to look for in order to avoid problems will be your best bet.

(post #107283, reply #4 of 7)

Since they were built as collar ties, don't assume those 2x8s are in line. Check them with a straightedge, string, etc.

And don't necessarily install the ceiling level. Compare the length of the rafters at both ends of the ceiling to see if one s noticeably shorter.

I put a ceiling in one half of an attic in an old house with a swaybacked ridge. The other end of the attic we left cathedralled.

I had to to install the ceiling with a slant of 2" out-of-level to avoid a noticeable trapezoid shape. It was a compromise: somewhat out-of-level and somewhat out-of-square.

It would have looked awful if installed level, but when we finished, it looked perfect.

If your ceiling goes the whole length of the house, check the middle, too: you might have to shim and furr the rafters into plane.

AitchKay

(post #107283, reply #5 of 7)

through bolt the 2x  collar ties,  skip the "vertical" you are talking about putting in from the joist to the ridge.  not necessary


 


if the rafters are sized right and not overspanned the ridge and kneewalls will stay putif you need to cut the span of the ridge down thats a different animal that none of us are going to touch without an archies stamp.  post pads footings everything then


you only talking about a few $$$ from 2x6 to 2x8 use the 8's to finish


 


Woods favorite carpenter


 

Woods favorite carpenter

(post #107283, reply #6 of 7)

The other answers here are good, but I just wanted to make it clear that whether your 2x8s are overkill for a ceiling frame is a moot point, they were installed as collar ties which are meant to keep your rafters from spreading apart. I wouldn't reduce their size, change their height along the rafters, or install any sort of vertical members down from the ridge without talking to an engineer first.

Justin Fink - FHB Editorial

Justin Fink - FHB Editorial

(post #107283, reply #7 of 7)

Collar ties don't exactly keep your roof from spreading. Rafter ties do. Collar ties prevent your roof from opening up in a negative pressure event i.e. tornado or hurricane. Rafter ties prevent your roof from spreading and are usually installed in the form of a ceiling/floor joist. Collar ties do have a secondary advantage of tying the two sides of a roof together which does prevent the rafters from sagging, but since they cannot transfer the load to the foundation like a purlin does this cannot be used as the primary purpose for their installation. Also collar ties only have to be a 1x4 @ 4' o.c. as they are not intended to carry any weight.


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