I'm a DIYer that's making plans to build a wood working shed in my
backyard. I do woodworking as a hobby but I've never done any
construction such as this. The workshop is going to be 16x24. I want
it to be very open and have enough room vertically for moving wood
around etc. I'm planning on building the roof using ridge board
construction. My question is can I build the roof in such a way that
I would not have to have ceiling joists? I would really like the
vertical space without having really high side walls.
The roof will have an 8/12 slope built with 2x6 24" o.c. and a 2x8
ridge board. Using collar beams would be fine since they would still
give me lots of vertical space. The side walls are most likely going
to be 9'.
I appreciate your help!
You are talking about creating a structural ridge. Your 2x8 is
not in the ball park. You are asking for something that can span
either your 26 or 16 foot dimension without sagging itself, able
to carry half the load of the roof, with enough lateral strength
to keep the side walls from bowing out.
Collar ties are not designed to prevent side wall thrust.
You may do better to contact a local wood truss manufacturer and
ask about cathedral ceiling trusses.
Keep the whole world singing . . . .
I don't know where you're located, but assuming a 30lb per square foot
load (average snow loads), your 16x24 roof would need to hold 11,520
pounds. A structural ridge would carry half that weight, the walls would
carry the other half. So, your ridge would need to support 5760 pounds.
According to my beam span tables, you would need a 6x12 beam spanning the
16' dimension to carry that load. If you want the ridge running the 24'
dimension, my tables don't go out that far, but I'm guessing you would
need a 6x16 beam or larger to span that distance (without a center post).
Probably a glulam or steel beam. Either way, those are some heavy duty
beams for a small workshop, and probably not an easy thing to install on
I recommend sticking with a traditional rafter/ceiling joist arrangement,
or order trusses. If you bolt the ceiling joist to the rafters at each
end (to ensure strong connections), you could possibly raise the ceiling
joists off the walls a couple of feet. But, it would probably be faster,
cheaper, and easier to order trusses with a cathedral ceiling. You won't
have much attic space with such a small building anyway, so you won't be
losing much with the truss webbing.
If you do use traditional rafters, you might want to bump up to 2x8's, or
space the 2x6's at 16" OC.
As for the ceiling height, I built my garage shop with 8' walls on top of
a 2' high perimeter stemwall foundation. After the floor was poured and
the ceiling installed, I have about a 9-1/2 foot ceiling height. I can
easily flip 8' boards or sheets of plywood end for end without hitting
I expect the 30 lbs/ft^2 above is 10 lbs/ft^2 dead plus 20 lbs/ft^2
snow. Even if there is no snow load, there is a "roof live load" of
20 lbs/ft^2, although for a single member carrying a significant roof
area (like a ridge beam), this may be reduceable somewhat.
I don't have the 2006 IBC handy. Does it really allow load reduction
for dead loads or snow loads? I've never seen that before. I've only
seen live load reduction for large tributary areas.
Generally, the IBC references ASCE 7 for loads and I see nothing in 7-05
that allows reduction of anything other than live loads.
No, the load reduction is only for live loads; it obviously doesn't
make sense to reduce a dead or snow load. Sorry if my original post
wasn't clearly worded, although I think it reads accurately.
Crap....I didn't know it was this difficult. I guess I'll just leave
the ceiling joists. BTW, obviously something important I left out,
I'm in the Raleigh area of NC so not much snow at all and the ridge
would run the 24' length. Thanks for everyone's advice. Obviously,
I'm going to need the help of a pro.
I didn't mean to discourage you. You can easily do what you want with
traditional rafters and ceiling joists, or have trusses made with vaulted
ceilings. A ridge beam just probably isn't the best option if you're
wanting to clear span the entire 24 feet. If you can add a post in the
middle you could bring it down to more reasonable lumber sizes, but then
you've got a post right in the middle of the room.
I'm no engineer, just an experienced amateur builder. The 30 pound load is
what we use locally as the "total load" for roofs. 10 pounds of that is
dead load (the weight of the building materials), the other 20 is live load
(the weight of snow, etc.). Obviously, if you're putting heavy tile on the
roof you'll need to increase the dead load, and if you get heavy snows in
your area you'll need to increase the live load.
Regardless, it would still take a rather hefty ridge beam to support that
roof, not to mention the additional foundation requirements to support the
loads at each end.
Let's get realistic here. The shed isn't much bigger
than a dog house. On my shop 24 x 40, I have 9'
plates/ceilings with joists every 4' with a drop in the
center of them down from the ridge. I air nailed the
hell out of them on the ends to the rafter and I can
hang a car engine in the center of the joist by the
If you put only joists every 8 foot on that little shop
that would mean only 2 going the 16 ft way and with 4 x
8 sheathing nailed really well, it will be there long
after you are gone.
Depends where you are. If snow load is a factor for instance. Where I
live, snow load is of no consequence here. This is important regarding the
roof framing structure requirements.
If snowload is not a factor, I would go with 2X6 16" OC rafters and ceiling
joists. 10' studs with fireblocking to address the overhead concerns. A
beam to support the ridge and joists. Put continuous studs under that wall
that supports the beam on both ends. Run a doubled up 2X12 beam across the
24' section midway. Put some mild 1/4" plate steel in it. 16' 2X12 will
work if on one side is centered, scabbed the remaining ends. And, on other
side 2 12' sections. Bolt together every foot top and bottom. Run a 2X2 on
the bottom both sides of the beam. Birdmouth the ceiling joists to tie into
the beam. Toss some plywood on the ceiling joists for a work area to build
the ridge, tack nail the plywood. Nail a 2X6 flat, on top of the beam, full
length of the beam, and nail it well. That 2X6 edge should be 3/4" offset
from center of the beam. Nail a 2X6 90 degrees with end up to the 2X6 you
just nailed to the beam (you'll see why in a minute, its standing up).
Double up 2 2X6s, nail together well. Cut down to the center, 1.5" slice,
the height of the bottom of the ridge board. The ridge board will be
supported by these during intial construction of the ridge, not for the ends
or where the 2 ridge board join. Temporarily brace these 2X6s accordingly
to get proper plumb and so forth. Mount the ridge boards, butt tight, ends
can run long for now. Tack-Nail the doubled up 2X6s to the ridge board.
Beginning at each wall, and working to the center, add a 2X6 every 64"
parallel and underneath the ridge board. The bottoms should be nailed to
the 2X6 that's standing on end I previously mentioned. These actually
support the ridge. Brace for plumb both ends of these added 2X6s. Remove
the temporaries. When done, add a 2X6 between each of these supports at
approximately 45 degrees. Starting at the wall, point on the beam to the
corner of the ridge and support. Run until nearing the center of the ridge,
do similar with other side. Effectively, a girder truss. Remove any
temporary bracing. Cut off the wild ends of the ridge boards. Add your
rafters. Pull up the plywood and shove it off. Frame any remaining wall
structures incidental to the roof framing.
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