Expert: Stephen Major (Owner--Major Design Group) - 8/29/2007

Question
I have a room that is 14.5 ft. wide by 26 ft. long and I wanted to remove the exisitng ceiling joists and roof rafters on about 20 ft. of the length of the room and stick build new roof rafters but not install any ceiling joists so that I could have a vaulted ceiling. If I run a 2x6 at the top to connect the 2x6 roof rafters will this be enough to keep the roof from pushing the exterior walls out? Also when I attach the 2x6 new rafters to a 2x6 ridge beam, can I butt (1) 2x6x16 ridge beam to (1) 2x6x10 ridge beam without having a support below?

Thanks for your help.
Jeff

Answer
Jeff,

No, you can't use a 2x6 ridge to prevent the walls from spreading.  It is not nearly strong enough at a 20 foot span.  The correct way to frame this depends on some information that you didn't supply yet.  What is the pitch of the roof?  Where are you located (for snow load and insulation considerations)?  What is the wall thickness?  What is the size of the existing rafters and ceiling joists?  

There are a number of ways to accomplish what you want to do.  A simple one is to use scissors trusses. These have a steeper pitch on the top than on the bottom, but you will still end up with a vault.  And since they are triangulated they will not spread if correctly designed.  

You could install a load-bearing ridge beam.  To do this you would need to beef up the end of the existing roof (the one that is staying in place) and bear one end of the beam on it (perhaps using a correct hanger paired with some doubled rafters and joists) and bear the other end on the end wall.  The size of the beam, and its bearing requirements, will be determined from the information asked for above.

Or, depending on the roof pitch, you could install collar ties partway up on the rafters.  Correctly designed, these can prevent spreading and still allow a higher ceiling.

So...let me know some additional information and I will be glad to advise you.

--Steve Major