ok without ceiling joists?

Posted by Greg on October 25, 2007, 8:59 pm

Hi,
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!

Thanks,
Greg

Posted by DanG on October 26, 2007, 6:45 am

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 . . . .
DanG (remove the sevens)
dgriff237@7cox.net

> Hi,
> 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!
> Thanks,
> Greg
>

Posted by HerHusband on October 26, 2007, 10:05 am

Greg,

> 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 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
your own.

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
the ceilings.

Anthony

Posted by Matt Whiting on October 26, 2007, 6:27 pm

HerHusband wrote:

> Greg,
>

>> 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 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.

What about the dead load?

Matt

Posted by Wayne Whitney on October 26, 2007, 7:15 pm

> HerHusband wrote:

> > 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.

> What about the dead load?

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.

Cheers, Wayne

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