Plywood gusset to assist undersized ridge?
The roof in my 80+ year old house was framed using a 1x ridge board that isn’t deep enough to even cover the ends of the mitered 2×4 rafters. I want to finish the space, sistering 2×6’s next to the 2×4’s. My engineer has suggested adding a ridge beam completely underneath the existing for the new rafters, but that will dramatically cut into my head room and is basically a show stopper. Alternatively, he suggested a plywood gusset strategy. Anyone out there have any experience or comments about retrofitting a ridge, or adding gussets in an attic conversion project? (house is 24′ wide, 8’4″ headroom at the peak in the current unfinished attic, 2×4’s 24″ oc)
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While I don't know about your
While I don't know about your attic intentions, 8'4" seems generous. A beam would be ... what 12" deep ... that's 7'4"; not bad considering even the 8 4 leaves you with headroom issues just inches away. While a plywood gusset may be OK, I'd have a tendency to go the ridge beam route. What's the span between end walls?
I want to convert the space to a bedroom. I have to add larger framing for the floor and ceiling, plus then subfloor, floor, drywall. If I'm starting at 7'4", I'll be at 7' or less by the time I'm finished. I calculated that the finished space would be 7'8" otherwise.
As long as there is no ceiling fan, a 7' bedroom ceiling is fine.
The point of a bedroom is to be mainly horizontal!
Been awhile since I dealt with this but IIRC code called for 7'6" ceiling height over at least 50% of the floor space.
7' ceiling may not be so fine.
I suppose it depends on location, of course. My house has 7' hallways and bathrooms. Hard to imagine an extra attic bedroom wouldn't be OK with a 7' ceiling.
Hallways and bath are not considered habitable space under the code.
Does look as if the code has changed, now it is 7' over the 50% of the floor space instead of 7'6" over the 50%.
However no floor space that has a ceiling height less than 5' can be counted towards the 50%.
http://evstudio.info/2008/10/20/minimum-room-sizes-and-minimum-ceiling-heights/
However not all jurisdictions allow that . NY State retains the 7'6"....
http://www.dos.state.ny.us/CODE/pdf/IRCCode%20CouncilChart.pdf
so the lesson is check with the Building Official to see what is legal in your area.
Which means he may have issues whether there's a ridge beam or not.
Another thought ... buy a little time from a structural engineer to let you know what is best for your condition. But as someone else pointed out ... there may be a ceiling ht issue that may affect your project in the codes.
Have your engineer spec a shorter and wider LVL ridge beam to add. Or even replace the existing, with carefully constructed temporary support.
You need a certain depth to the roof rafters so that you have enough insulation. Proper amount of insulation goes a long way to lower heating *AND* cooling bills.
Consider spray foam or cellulose. Fiberglass is the last choice. Add a 1 or 2 inch layer of PIC board (poly isocyanurate) sheets on the underside of the rafters and then put your drywall sloped ceiling. You'll be cooler in Summer and warmer in Winter.
IMHO plywood gussets would do absolute nothing to strengthen the assembly.
They might take the place of collar ties for wind uplift, but nothing more.
If you have a conventionaly framed roof, a 1x ridge board is not a problem, seeing ridge boards have little to no structural value when it comes to load bearing - provided rafters on either side of the ridge are aligned. The fact that the ridge board is not tall enough to reach the heel cut of the existing rafter is a slight problem.
My suggestion is to go ahead and sister in the 2x6 rafters, making sure they fit snugly against the existing ridge. When you have finished framing one side of the ridge, slip a second 1x ridge board up to the bottom of the existing ridge (make sure the height of the new ridge board extends at least to the heel cut of your 2x6 ratfer). Face nail the new ridge into the new rafters, then complete the framing on the opposite side. This should minimize the overall drop in headroom. If you are removing rafters to dormer certain areas, this will NOT work.