Roof pitch and truss questions (for a shed)
Hey guys, I'm working up a plan and materials list to build an 8x12 shed on our property, and I'm trying to figure out the best way to calculate for building the trusses and what pitch to make the roof. Cabin is located north of Talkeetna; annual snowfall is 120 inches, according to NWS.
I already have roofing material, salvaged from another shed. It's corrugated metal in 3 ft wide by 10 ft long strips. Allowing for a 1 ft eave/overhang, that gives me about 9 ft of roof from the peak to the walls. I did some math work on paper, and I can use an 8' post at the center of the two ends of the shed, and that will create an equilateral triangle with an 8 ft peak, and 8 ft base, a 63 degree slope with a 1 ft overhang. (I'm doing a bit of rounding here, every dimension had some fractional inches in it.)
So my concerns are: doesn't that seem like too steep of a roof and too high of a peak? And...how do I build trusses for that?
If I build with rafters, how far apart do I spread them?
Do I place trusses every 16 inches, inline with the wall studs?
What's the best way to connect the horizontal rafter to the diagonal?
Do I need to run a ridgepole along the top or can I just tie all the trusses together with 2x4's across the gap?
If I DON'T use rafters (vaulted ceiling) how big of a ridge pole do I need? (I'll likely make that with a chainsaw mill and a large spruce tree.) and how do attach the diagonal beams to the ridgepole?
Can I build a vaulted ceiling, but use horizontal rafters, with no supports, so as to make a loft?
Economically speaking, is it cheaper to build my own trusses, or just go buy them from SBS?
For a shed of that small size you are putting way to much engineering thoughts into it.
Originally Posted by Big Bend
Perhaps it's a learning experience prior to building a cabin.
Here is a nice site on pitch.http://roofgenius.com/8_12%20Roof_Pitch.asp
Originally Posted by FL2AK-Old Town
Most people place rafters every 24" and that can vary with what you are using. A shed that size with a roof as steep as 6/12 or more can be fine with 2x4's. Trusses are easy to build onsite as long as you have the dimensions and use a pattern. Can use nailing plate or make your own with simple dimensions of plywood for gussets. Easy to do a W support system. Can pre-cut and basically make an assembly line out of it with one other person and 2 sawhorses with plywood sheeting to lay them out. I just did this for a 12x16 cabin and it went very smoothly. I will use a ridgepost for my larger cabin build in the summer and will use larger rafters and ridge as I want to have loft as well as vaulted ceiling. FWIW we put trusses 16" apart for snow load. If you want to put trusses- toenail or screw strips of plywood across them to keep them from shifting and then once the roofing material goes on it is stable. I think building a shed in preparation for a cabin is a great idea. Don't be afraid to look at some good books and videos- lots out there. If you are building this winter and need an extra helper- just let me know.
Wow, thanks for the offer, Bee. Awesome. I hadn't plan to build till spring. I'll be outside till mid January. The building site is a ways back off the logging road. I can drive to it in summer, but would need a snow machine in winter. (and I don't have a snow machine.)
I already have a "tent platform" back there that I am going to wall-in and roof-over, so I need to frame up some walls, and I need to figure out what to use for a ridge cap where the corrugated sheets meet at the peak. Plan to build everything right on top of the platform that is out there now.
Building on the platform is good. Can do the trusses first to have room to maneuver them (if deciding on trusses) and then set them aside well supported, and the walls are a breeze to do. I have a ton of work to do on my place as soon as the snow is thawed but if you have materials handy we can knock out the walls and rafters/trusses in a day.
Where are you building at? If you need a hand, perhaps for a day, I could come out and learn a little.
Originally Posted by AKBEE
By the way, I found a book on home construction that has a good section on framing in it. It has those tables with allowable spacing between trusses based on snow load and material type. 2x4 barely fits in there for the dimensions and roof pitch I'm building if using pine or spruce.
I am going to use rafter trusses. From what I've read, that will eliminate the walls being pushed outward, and will let me store stuff up there.
I'm considering milling my own lumber for this. As near as I can tell, I only need about 50 2x4x8s for the whole project plus 4 2x4x12's. Would probably save me about $200. The siding is the spendy part.
My land is about 8 miles east of the hwy taking Hidden Hills. We had a heck of a summer with marking/walking the trail in to my property and through it to my neighbors, cutting/felling trees on the path, then widening for ATV's, cutting/felling for cabin sites, then my neighbor used an excavator and a dozer to blaze a nice drive in and leveled building sites. Never dreamed I would cut so many trees! We got his 12x16 starter/guest cabin up and will finish it this spring. He is out there now doing wiring for the generator and outlets and overheads. I will be putting up a shed at rhe beginning of the season, and then start on cabin. I haven't decided on what size I want to build yet, but likely about 16x24 or so. I don't need anything big but it would be nice to have room for friends. My neighbor will be building his 'actual' cabin the following year and plans it to be about 1500 sq ft. You would be welcome to stop in anytime next year. I admire your aspiration to use your own lumber. I want to do that and plan to use some of the rough sawn for siding. The idea of using lumber you cut down to build is awesome, but I am a bit impatient so will frame with store bought for now...
Originally Posted by FL2AK-Old Town
16 x 24 I think is a popular size. My girlfriend's dad's cabin (on the same property) is 16 x 20, and I often wish we had that extra 4 feet.
Yeah, chainsaw milling is slow, plus my saws are undersized for that task so...even slower. I'm getting the hang of it. I would mill clapboard siding pieces instead of using siding from HD/SBS, but I'm afraid that much milling would burn the saw up.
When I travel to Tampa next month, I'm going to Northern Tool and buying the Mini Mill to go with my Alaskan Mill, and bringing it up on the plane in checked baggage. Then I'll be able to mill D logs. But that's way off in the future.