A 12x16' roof can hold a lot of snow! :)
When you start calculating the loads a structure can support, it's really
kind of amazing how much weight they hold without collapsing.
Actually, if you make the end walls with 2x6's, that would put your free
span awefully close to a 15 foot span. A couple of 16 foot 2x12's should
carry that load OK if you really want the open roof structure.
It's easier, and stronger. That's what I opted for too... :)
You can also gain a little overhead storage if you plan the ceiling
If you need more headroom, just make the sidewalls taller.
Generally, the ridge is one size larger than the rafters. For 2x6 rafters
that would be a 2x8 ridge board. Of course, if the roof slope is really
steep, you might need a 2x10. Basically, the ridge should be at least as
tall as the vertical cut at the top of the rafter.
On my garage (24'x28') I used 2x6 rafters, a 2x8 ridge board, and 2x12
ceiling joists to clearspan the 24' and provide a usable attic.
However, when I built my shed (8'x12'), I made some simple site built
roof trusses. No ridge board needed. You could always order trusses from
a truss company too.
For a 12' deep shed, I'd use 2x4 rafters, a 2x6 ridge, and a 2x6 ceiling
joist, spaced at 24" OC. If you want to increase the strength, decrease
the spacing to 16" OC and/or use 2x6 rafters with a 2x8 ceiling joist.
If you think you might insulate the shed someday, you might want to think
ahead and use rafters or joists that will provide space for insulation.
For example, I installed 2x12 rafters on the cathedral ceilings of our
house, even though I only needed 2x8's for the span. That let me install
R30 and still leave airspace under the sheathing.
One final option, you could put a "shed" roof on your shed. Basically,
make the front wall taller than the back wall, and set your rafters
directly on the walls spanning front to back. Strong, easy to build,
inexpensive, and provides high ceilings. You could even install windows
in the upper part of the front wall to let in additional light. The
biggest downside.... It looks like a shed (or a chicken coop, depending
on your viewpoint. :) ).
I built a 12' x 16' shed that turned out to be a pool cabana. The 16'
foot length has an 8" x 2" ridge beam. The ceiling is a cathedral
ceiling with insulation and wood paneling and there are no collar ties.
The shed is about 18 years old now and there is no noticeable pushing
out of the side walls. The paneling is painted and there are no visible
signs of paint cracking on the edges. I live in NY which does get snow
falls of 12" to 16"
Is the wood paneling nailed to all rafters? Were the rafters what you call a
cathedral ceiling? What thickness is the wood panels? Are they considered
as roof sheathing nailed to each rafter? Did you have other sheathing on
top of the rafters?
I think that you had a internal/external diaphragm on the rafters which
resisted the lateral component on the walls and distributed it to the end
walls. What were the end walls framed with if plywood they act as shear
walls to resist the end reaction of the diaphragm. You had the resistance
somewhere if no wall deflection was noticed.
Yes, 4' x 8' x 1/8" plywood wall paneling, grooved like wainscoting, to
all rafters. Nailed with 1" panel nails about 4" spacing along each rafter.
Yes, with the paneling attached.
They are nailed to each rafter as paneling.
3/8" plywood sheathing with asphalt shingles on the roof.
1/8" plywood paneling
Just in case there are other questions, the shed was built to the usual
housing standards (other than the foundation, since there is none. The
shed joists just sit on a bed of gravel). 2 x 4 studs 16" OC center. The
floor joists, underlayment and wall floor plates is PT. the roof pitch
is about 4/12. The ridge beam is 2 x 8", the rafters are 2" x 6", 16"
OC. The insulation between the 2 x 6 rafters is the usual R-13, 4" x
16", fiberglass to allow a couple of inches for air circulation between
insulation and roof sheathing. Soffit vents and ridge vent for air
circulation. Also has a working cupola that was used when it was an
unpaneled and uninsulated garden shed. The cupola still works but it is
not open to the ceiling, only to the air space below the roof sheathing,
as does the ridge vent.
I am sorry but a 2"X8" ridge beam spanning 16'-0" is not enough for what you
are describing. You are going to have wind and snow loading on the roof.
The snow can drift on one side of the roof if there is wind forcing this
situation. Unbalance loading with wind loading more wind pressure is on one
side of the roof which causes loading on one set of rafters and not on the
other. Not to mention the critical conditions for wind that are along the
gable ends and corners of the building. These are the first areas that you
will find damage in a critical wind storm.
By the way a 3/8" sheathing is a good diaphragm for what you are building.
OK lets get real here. We are talking about a run of 6' on the
rafters, pitch unknown. The length of the wall is only 16'.
That's not much more than a dog house, Plywood sheathing nailed
right even with no ridge would hold it. I would put a tie down on
the plate every 4' but it really isn't needed for something that
Wow, that seems like a really undersized beam if it's spanning the 16'
dimension of the shed. I'm surprised it hasn't started sagging over the
I can only think of a couple of reasons why it's still sound:
1. The connections at the ridge are so strong that they can't pull apart,
and thus the ridge can't drop. But I'd think that would take some steel
brackets to pull off. I have a 8'x8' pump house which uses brackets like
this to create a gambrel shaped roof without using any rafter ties. It's
the same approach most "shed kits" use, except they usually use plywood
gussets instead of metal brackets.
2. The building is almost square and the top plate of the wall is acting
like a ring to tie everything together. Kind of like the way a gazebo stays
up without rafter ties. Essentially, the side walls keep the front and back
walls from moving outward. This would only work if the building was small,
and the top plates are strong enough to resist the sideways pressure from
the rafters pushing out.
Then again, it could be the combination of all three, the ridge beam, the
connections, and the top plates that are holding it all together.
I'm glad it has held up for you, but I wouldn't design it that way. Then
again, I'm no architect, just an amateur builder...
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