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'.
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.
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.
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 drop.
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.
"Greg" wrote in message news: snipped-for-privacy@19g2000hsx.googlegroups.com...
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. Dave
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.
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.
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