Hello, been following forum for some time now and enjoy it, finally have a real question concerning roof framing. Boss has just made me a ‘stupidvisor’ and the job has some concerns for me. Front gable end view is 5 in 12 pitch spanning over 30′, so rafters will be close to 20′ with overhang. The room on the right side is 12′ wide and architects drawings call for cathedral ceiling with ‘dummy’ rafters giving the inverted vee ceiling. Room in middle is about 16′ wide and far left is 4′ wide staircase to basement. I’m concerned that with no continuous ceiling joist system spanning between the exterior side walls there’s a risk of them bowing out in the middle. Needless to say were saving the customer money by not having structural drawing details. I’m sure boss would like ceiling joists for flat ceilinged 16′ wide room running perpendicular to rafter so we would only need 12′ material. Questions are, do I worry about side walls bowing out under load, and since there are ceiling joists in one room only does it matter which way they run. Oh ya, and should we be using 2 x 8 or 2 x 10 rafters, were in North Carolina, not much in the way of snow loads.
Thanks in advance for any feedback. gdcarpenter.
Replies
Sounds like a pretty slipshod way of running a business. If the customer has gone to the expense of hiring an architect for a 12x30 partitioned room a couple extra bucks for a structural plan shouldn't be a big deal. I would think that this would be part of the architects package, too.
This looks like a perfect opportunity to spec a truss package. If I brought the dimensions to my truss plant of choice I would have a FREE set of stamped truss plans in a couple of days. Then the PE would incorporate them into the overall structural package and I'd be good to go.
FWIW, I would throw the problem back to your boss. You should not be reponsible for building from incomplete plans. Too much can go wrong, especially when you feel the need for structural advice from this forum.
Gotta agree with Ralph. And how did you plan to get a building permit without showing the direction, size, etc., of the framing, anyway? Sure can't get one without it here in NJ....
Bob
Trusses would certainly be an option.
But a structural ridge beam would also prevent any horizontal thrust at the walls.
What do chickens think we taste like?
Thanks all for the feedback. Trusses are rarely used in residential work here in Raleigh, NC. Had a powwow with the boss today and we'll be stiffening up the ridge beam significantly and have figured how to implant some collar ties. Don't need detailed structural drawings for a permit here, have seen hand drawn plan and elevation views, with no details sort of rough dimensions, get a permit. The inspectors do eyeball things pretty scrutinoulsy in the field though.
thanx again
I build in charlotte, NC - would definately use at least 2x8, 2x10 would be better. Two things to avoid the walls bowing out - Structural ridge - some sort of LVL. Also on the exterior wall you can install a steel angle and bolt it to the topplate - this will keep it straight.
One thing though, I use to build in Cary and the inspectors there are the worst I've ever seen. Hope Raleigh isn't that bad. In charlotte, anytime you use engineered lumber you need a sealed drawing from lumber manufacturer or structural engineer.
Don't forget your hurricane clips.
Convinced boss to go with LVL ridge, and since some of the rafters form part of the cathedral ceiling we need 2 x 10 there to get R30 so we're going 2 x 10 all the way. Not sure if the boss knows that we're going with 2 x 6 collar ties but I did the material takeoff, so 2 x 6's they'll be. To his credit boss usually overbuilds anyway, just the new guy on the crew who's quite the hustler is promoting the word economy more than quality. Guess it's a fine line for some. Haven't ventured as far a Carey to build, but wife just took a new job 'out there'
Inspectors are tough but an okay bunch sofar. Been dinged on the collar ties enough that they are programmed in now.
Thanks for all the advise.
Just remember that a structural ridge beam must be supported continuously though to a footing in the basement. The use of a structural ridge beam then cauese the rafters to push the walls in rather that out as they are supported at the top. I just finished intalling a 48' 31/2 by 11 7/8 lvl ridgebeam (in two pieces) for a current reno we're doing with handcut 2x12 rafters on one side and low slope trusses on the other. Around here handcut roofs are the exception, tusses are used everywhere and you need an engineers stamp on any roof construction. Happy framing.
John Quinton
Quinton Construction
If roof trusses are available anywhere within 200 miles of your project I think you owe it to your crew and customer to look into it. It should be the best and least expensive way to build what you describe. A strong ridge has little to do with keeping the walls from spreading out although you are on the right track with collar ties. Maybe one of us should open up a truss plant in your area. Enigneering help is cheap insurance.