Expert: Dave Johnson - 8/26/2007

Question
QUESTION: I'm looking for increasing an existing stud walls height from 8 ft. to 9.5 - 10 ft around the house perimeter. Existing roof will be removed and new will be built. Can I just simply build another short wall framing on the top or perhaps there is a way of designing trusses that would increase the ceiling height and seat on existing 8 ft. wall?

ANSWER: Hi Bogie,
There are trusses called "scissors trusses" and are for cathedral ceilings. They are usually half the exterior pitch on the inside.For example: a 6/12 roof line would give you a 3/12 cathedral ceiling.
I think this is the way to go, because adding a short wall on top of the existing would create a "knee" and
cause you to have a VERY weak wall.
a 3/12 ceiling in a house 26' wide would give you 39" in the center.
Hiope this is clear, please mail me if you need more.....
Dave



---------- FOLLOW-UP ----------

QUESTION: Thanks Dave,
I'm familiar with scissors trusses. They are a good solution for increasing the room volume, but I'll still have ft high wall around the perimeter. My new space will be joint living and kitchen that will be quite long and 8 ft may create "tunnel vision". What about increasing wall height just by 11 1/4" adding two 2x12 on the top of existing double top plates? will that be stable?
ANSWER: Hi again,
I still don't like it, it makes a weak place at the joint.
Is there any chance you could cut through the existing top plates every 32" to tie some vertical members down into the wall to stiffen things up? If you do this, don't skimp on the fasteners.
Best of luck, Dave

---------- FOLLOW-UP ----------

QUESTION: Dave
...hmm. It looks like you don't like my idea. I've seen this idea placed in your expert forum, so I thought 2nd opinion would be good. Correct me if I'm wrong; if you had to place a beam, say 2 or 3 2x12 on the top of existing wall for the purpose of extending it past the wall (cantilever roof or similar structure), would it be that okay and only one solution?

Answer
Hi, You're right, I don't like it....I can't get past this joint between the existing wall and the "addition".
My concern is a rolling effect here when stress happens,
like severe winds etc.
You see, there are no through fasteners, everything breaks at this joint...frame/sheathing/drywall....