Hi. I'm planning on building a garage 28'x36' with a 12/12 pitch roof.
I expect the room upstairs to have what I guess would be called "knee
walls". I was at Lowes and they got me a quote on trusses but didn't
get me the dimensions, so I have no idea how high the knee walls would
be. What would be a common height of knee walls? Or a range of
different heights applicable.
With the 12/12 pitch, I assume that for every foot high the knee wall
is, the room will be 2 feet narrower then the 28' garage width.
(compensating for both sides)
Thanks for any help or suggestions.
I was also looking at local model garages from a company that only
builds garages. They had a 24' wide one with 3 foot high knee walls
directly above the first floor walls, then the roof on top of that. I
forget the pitch, but the roof framing was 2x10's going to the peak,
with 2x6 collar ties 9 foot up from the floor. So the angled part of
the ceiling went from 3' to 9'.
Maybe it was plenty strong, but to me it looked like it would eventually
sag. Especially with the weight of drywall up there. (the model was
not finished inside). I was thinking of doing almost the same thing,
but the framing would be balloon style with 12' studs on the first floor
and the floor/ceiling joists would be at about 8 feet. That would give
the little knee wall a hell of a lot more strength to prevent it from
sagging and bowing out. Am I worried about nothing or does the need for
more strength sound like a good idea?
a knee wall is what you make it, any height you want.
With 12/12 pitch and no knee wall you will loose 6' of useable all the way
around the room, (considering anyplace the ceiling is less than 6/' high)
making your usable room 16'x24'
less your stairwell area.
Making your knee wall higher gives you more floor space.
Ass far as sagging or bowing, make sure you have your project engineered and
built correctly, you should have no problems whether you balloon frame or
It seems you are confused about "attics" in conventional framing
versus trusses. In conventional framing the kneewall is a wall over
the exterior wall raising the roof framing to get the desired usable
space underneath. Partition walls are built within the attic space to
define the usable space and minimum ceiling hieght. So your idea of
ballon framing to 12' and installing the floor joists at 8' would work.
With trusses the kneewall and the partition walls are built into the
truss and are both structural elements. The room width would be 1/2 of
the truss span, although I have designed attic trusses with attic rooms
up to 2/3 of the span. Consult with the truss manufacturer. To insure
you get what you want out of a trussed attic, draw a profile including
the ceiling hieght, the room width and the minimum head room desired.
Then try to talk to the truss designer assigned to your project.
Unfortunately salesmen do not usually know that much about the
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