Raising Ceiling Joists

lou94stang

I spent days searching and reading up on this topic and am finally gonna post my topic and see if I can get some definitive answers. I currently have a 25' wide X 40' long 1 1/2 story cape with a 2x10 ridge that has one side dormered for the total 40' of the house. It is a shed dormer with a 2.5/12 pitch and the undormered side is a 10/12 pitch. The current ceiling height is 7'6" from the floor to double top plates. The rafters are 2x6 16" OC. I am about to dormer the other side of the house to match the opposite 2.5/12 shed dormer. So my question is since I am cutting the old ceiling joist out anyways is it possible to raise them 1/3 rd of the way up nailing to the 12 1/2 foot rafters instead of the top plates so to raise my ceiling height to 8'. The new ceiling joist are gonna be holding sheetrock only no storage so I was thinking 2x8 #1 dug fir for the 17' or so feet it will run. Also the rafters run parallel with the joist.

knucklehead

Sounds like it would work. You maybe want to use 2x8 or better for your rafters, since they will become part of the ceiling AND they will be carrying your ceiling

Windwash

Hey Lou,
What part of the country are you in/snow loads? You may need to put in a structural ridge ( it may need it now with only with only half the roof dormered).

If you want to gain additional ceiling height it may be easier and more cost effective to rip the whole roof off and install trusses (your already replacing half the roof) if you can raise the total height of the structure. Bring your measurements to your lumberyard and they will be able to find provide quotes for trusses.

2.5/12 pitch isn't great for most shingles, so the additional slope provided by new trusses would be a bonus for the longevity of the roof.

Warren

2 words.....................Structural Engineer.

ClemS

double up the ridge when you yank the 10/12 and post it at the stairwell to your center girder. then put carriage bolts through the ceiling joist into the rafter for good measure.
should be in top shape with that.

themurphyco

If you can afford to insulate the whole project with polyurethane foam,not icynene, it will pay for itself in two ways. First it will turn the whole roof into a SIP. Second, you don't need ridge or soffit vents and thirdly. Your upstairs will be much cooler. I do alot of old houses that are well below structural guidelines when it comes to load and span and the foam works for me everytime. I even had a teenager drive into a post holding up a sunroom and the room didn't collapse when the post was knocked out.

lou94stang

Thats what I was thinking to do. I was gonna double up the ridge with some lvl and then carry the load down wherever possible to the bedroom walls that are gonna be right under the ridge, Which in turn should spread the load out to the 2x8 floor joist underneath. i should be able to get at least half of the dormer posted down to bedroom walls. Where I am in Long island NY this is type of work is done all the time most of the houses are typical 1 1/2 floor capes. I have had several old school builders in to quote me on the job and they all have done this type of dormer before and raised the ceiling with out adding structural ridge. To tell you the truth I would go with a hands on old school builder before any pencil pushing engineer that never hammered a nail in there life.

naptown CR

At that low af a pitch i would have to agree with this or replace the whole roof.

ClemS

i do quite a bit of work on long island.

it's been deemed a hurricane zone for the past some-odd years so there's all that metal strapping to contend with now. which town are you in?

personally i feel that i have a much better grasp on reality of building & structure than most architects/pe's that i come across. there are some exceptions of course but most all of them who do residential work are worthless and very thick-headed to boot. (not that I'd ever fathom making them feel that way)

but if you go through the process of having plans drawn and submitted to your municipality for approval, you're likely to have several issues. first and foremost is the r-value of your new splayed ceiling - they'll want r-30 which mean you'll need to pack your 2x6's down to a 2x10. secondly, they'll want hurricane ties on any affected areas.

as far as old-timers go - they do tend to under-build things. as a rule they have a great deal of faith in posting down to nothing, which creates all sorts of problems down the road. like I said before, use the center girder in the basement to take a couple of point loads from the ridge, and provide adequate connections at rr/cj and you'll be okay. with the kind of snows we occasionally get around here you should put ice/water shield on the entire roof in lieu of felt.

lou94stang

What would you consider adequate connections at rr/cj. Nails and glue or simpson strong ties or both. Also definitly gonna do ice water shield.

ClemS

i would nail them on, and then add a 1/2" through-bolt at each connection for good measure.