Rafter help

I'm building a new shed, 12' wide and I want to do a 7/12 roof. Do I need a ridge board? Do I need to use 2x6 or will 2x4 work for the rafters. Explain to to me like I know nothing about carpentry please.

Thanks

Have you considered just buying them? You can get 12ft rafters from your big box lumber stores. Otherwise there are videos on you tube that would be helpful.

I looked at a span chart briefly and i would go no less the 2x6 for rafters. With a heavy snow load 2x8 might be better but with your 7 pitch it will probably ride. You will need a ridge beam. Old schoolers used a 1x but i think a 2x is better as well as it being deep enough to capture the whole cut of the miter on your rafter. I think collar ties are good too. Essentials the board going from one wall to the other horizontally capturing both rafters and wall. When loaded the roof wants to collapse and push the wall outs. Collar ties resist this force. All said if you nail and brace well 12’ wide is pretty minimal. Good luck

I would use 2x6 rafters, and a 2x8 ridge. 24" centers, 5/8" plywood.
Use NAILS, not screws.
Do yourself a favor, and get what is called a "speed square", which will make your ridge cuts simple.
Seat cuts, (the part of the rafter that sits on the wall), are a little trickier. For a shed, I would just not bother, and use H-1 Simpson brackets, and 2x6 blocks, (22-1/2"), between the rafters.
You can make collar ties, or span wall to wall with 2x material for ceiling joists.

Thanks guys. I made the side walls from 2x4, 16" on center, is it okay to put 2x6 on top of the 2x4 walls?

No point, you only need 1 inch of bearing, and the overage will be unsupported anyway.

This is what I got so far. Its a 12x18 which falls just under needing a building permit. Floor is sandwiched between 3/4 green treated and insulated. Putting 3.5' barn doors on the front so I can bring in my small equipment to work on.

first question what is your snow load ?
typically your building code will tell you what snow load you need to build for you area.
then you can drop that info in rafter or truss calculator.

you actually go wider than the 12 feet because you want some overhang but given a 7'6" interior height and an interior width of 6 feet your looking at about a 15:12 pitch roof.
I assume you are doing this to get attic space for storage , you probably want a gamble roof a "barn roof" this gets you more useable space and typically you build them as trusses so then no ridge pole is necessary

I was imagining no real ceiling, just leaving the inverse V more less and not running a board on the bottom of the truss or top of the wall.

Edit. If I'm trying to do something moronic please tell me, I've never done this type of work.

With snow load there's really no way around 2x6 and 2x8 ridge, 24" or 16" oc. Up the plywood to 5/8 or 3/4 if going 24"oc and 16" is iffy for 1/2. You will also need wind ties and or ceiling joists as well.
One advantage of ridge vs no ridge is that each end of the ridge is fully supported at the end walls carrying the load of all of the rafters.

Now down here without snow 2x4 without ridge 24"oc would suffice with good wind ties, I would scab plywood triangles for wind ties. But I would still use 2x6 with ridge.

so your doing this to get a high ceiling to mount your skinning rig from?

you want a tie from side to side about every 6 feet or your inverted V pushes out the walls

at 15:12 you wouldn't keep much snow on the roof that is for sure

so you need to answer some more questions , how long is your building? you said 12 feet wide

what type of roof do you plan to put on it , metal , shingle , shake ?

a book that might help you is . A Graphic Guide to Frame Construction

You really need the joists or wind ties. If you can picture it, the weight of the roof is pushing straight down. An inverted V wants to spread and flatten. Without joists at the wall top or ties further up the rafter the walls will eventually bow outward and fail. The taller the rafter the lower the tie needs to be without joists.

The only other bracing that'll offset the bow is internal cross walls with sheer bracing, such as being sheathed with plywood. But even then the roof can still move off of the top plate as only the fasteners are holding.

The building is 20' long. Hoping to do metal roof

If I put a small loft in the back say 6 feet of the building would that be enough to keep it from being pushed out?

I think I'm starting to understand what you guys are trying to tell me. I could still have no ceiling but have a 2x6 across every 6' the length to hold it all together. I was hoping for the high ceiling to hang all my antlers and skulls up there more than anything. Also hoping the snow would fall off without needing to go rake it

metal roof or shingle roof?

exactly and since it has no weight bearing you can actually use a 2x4 although a 2x6 would let you hang more stuff from it

also are you finishing the ceiling , insulation ?

Metal roof and it will all be insulated

when you do a metal roof you could do two trusses in the middle and use purlins to bridge them all this is how pole barns work not at all uncommon to have a 8-10 foot span between trusses on a pole barn.

This is how my house is done and how I redid my roof framing. The birdsmouth cut is actually done using the same speed square and is really simple once you understand what's going on. For a new shed, he just needs to look at the rafter tables to see how he needs to cut his ridges and birdmouths. Larry Haun has a great video on youtube that is about 40 minutes long but it really shows everything you need to build an entire house.

Speed squares are nice but I did all my rafter and stair layout with a framing square.

For a straight gable run lay out a pattern rafter make a duplicate, check fit, then use pattern to mark the rest.

I would go 12:12 it makes everything a 45 or right angle for cutting your birds mouth simplifies calculations plenty of slope to have a tall ceiling
I would also put a double header on the top of that wall to better distribute the weight if you don't have a rafter right over a stud.

I would also set up to hang over front and back and each side, more on the front to limit how much rain runs down the door , shooting that snow further from the building preserves your siding and foundation

are you going with steel siding also?

Just build yourself some trusses or have them built. 2x6 rafters and bottom chord. 24" centers. No plywood roof deck. All that does is add dead weight. Use 1x or 2x nailers every 16" and screw your tin to that. It will be plenty rigid once the metal is attached. Hurricane ties at the eave on every other truss.

Will be adequate for snow up to 30 psf live load and 10 psf dead load.

You really cant do a vaulted celin (uspside down V) without some sort of engineered parallel cord truss. I agree with white, you should see if someone can build you some trusses. It would take a while for that in my neck of the woods. Otherwise, throw up your gable rafters and ridge beam(another guy would be very helpful) then fill in your field rafters. Cut you collar ties/horizontal ceiling joist to your building’s spread. Might have to miter the ends for where the eave is. This will give you a consistent reference of your spread on the top plate. Some bracing would be good to before you do all this

I left my attic space open on my garage, put blueboard foam in between rafters for a little R and put sheets on top of collar ties for more storage. I did put 2x6 for collar tie because i like to store heavy items up there when out of season. (Traps, decoys, blinds, oars, etc)