I need help, adding a roof to a deck

[bigun]

I'm sure I asked this before, but I need to add a roof to our deck. It is 30 feet long by 12 feet wide eventually I will probably turn it into another room, but right now I need to get it covered, because in the winter it gets covered with ice, and I'm afraid one of these days mom is going to get hurt slipping on it. I want to use 2x6s for the rafters and 4x4 for the posts and I want to make as few cuts as possible. Part of my problem is at the roof of the house it is 7'8" I would like to keep at least 6'4" of head room at the lower end if possible, I would also like to use as few posts as possible, to keep the view open as much as I can. For now I am thinking about using 1/2" OSB to deck it with roll roofing, but when we have the money I'll go a head and cover with metal roofing. I am not a framer nor engineer by any stretch of the imagination so make you reply's as simple as possible. Thank you
Charlie

[bigun]

Well here is what I've come up with. I'm going to take a 2x12x12 mark down 4" from each side on opposite sides then pop a chalk line this will give me two rafters per board with a flat bottom, they will but up against a ledger board bolted to the existing rafters and be held in place with joist hangers, on the other side I'm going to use 4 4x4s or 6x6s set at 7'8' apart and have a double 2x6x8 sitting on to the rafter will sit on top of this again held with hangers and screws. I'll top the thing 7/8s osb and 15 pond felt topped with 40 pound coated for now.

[HOOT]

I think I would go metal from the start. You wouldn't need the OBS then. Or am I wrong about metal roofs? You guys don't get gobs of snow do you?

[bigun]

I think I would go metal from the start. You wouldn't need the OBS then. Or am I wrong about metal roofs? You guys don't get gobs of snow do you?

Still need an under layer I think, right now I'm trying to fund with what we have on the HD card. I may have to wait a month or two to complete which is why I was using felt. Pricing it right now. We can get some deep for us is a foot or so

[HOOT]

I also forgot you may want to enclose it. definitely would want something up there then.

[Tatsadasayago]

WIth an average 12" of snow/ice on top, you should consider designing with a 20-40 pound per Square Foot snow load. Your 2x6"s at 12 feet in length at 24" centers are good for roughly 20/PSF which is on the minimal side. The other thing to consider is bracing your posts to address the shear forces. If You are going to tie the roof to your house, that will stop shear on one side, but the outer posts will need to be braced. The reason for this is having a snow load on top, plus the dead weight of the structure, add some wind and you have some serious swaying potential. Some 2x4x4' angle braces at each post would go a long way toward keeping shear/movement to a minimum.
How are you going to mount the posts? Tie into the existing ones or sink them at the perimeter of the deck?

The OSB would go a long way toward dealing with snow/ice load as well as keeping shear down in the horizontal direction ie; boxing the roof so it stays square. I've seen many metal only roofs go to hell in just two years from the loads which caused bowing, loosening and even bending.
Since your roof won't have much pitch, the rolled roofing will do okay with rain, but come winter, you would do well to have some metal on top of that.
Don't forget drip molding to protect the OSB edges from moisture.

[bigun]

WIth an average 12" of snow/ice on top, you should consider designing with a 20-40 pound per Square Foot snow load. Your 2x6"s at 12 feet in length at 24" centers are good for roughly 20/PSF which is on the minimal side. The other thing to consider is bracing your posts to address the shear forces. If You are going to tie the roof to your house, that will stop shear on one side, but the outer posts will need to be braced. The reason for this is having a snow load on top, plus the dead weight of the structure, add some wind and you have some serious swaying potential. Some 2x4x4' angle braces at each post would go a long way toward keeping shear/movement to a minimum.
How are you going to mount the posts? Tie into the existing ones or sink them at the perimeter of the deck?

The OSB would go a long way toward dealing with snow/ice load as well as keeping shear down in the horizontal direction ie; boxing the roof so it stays square. I've seen many metal only roofs go to hell in just two years from the loads which caused bowing, loosening and even bending.
Since your roof won't have much pitch, the rolled roofing will do okay with rain, but come winter, you would do well to have some metal on top of that.
Don't forget drip molding to protect the OSB edges from moisture.

I guess I'm over building because I was figuring on going 16 inch on center. I have only seen 12 inches here once, but I have heard of much more in the 1980s deep enough for the national guard to be called out to help ranchers feed their cows. Yeah I knew about the shear problem, I wasn't here when deck was built but I've seen the plans my dad drew up,. It sits on 4x4s concreted in then there are joists running parallel to the house and the floor is 90* to the joists, I'm planning on laying down a pressure treated 2x6 then using Simpson tie securing the posts to it in fact the Simpson company will be making a few dollars off this build because I don't want it to fall, If I had the money I would continue the deck all the way around the house. I knew about the drip molding in my mispent youth I worked for as while as a roofer that is till I got in a fight with a bucket of hot mix

[Tatsadasayago]

Better to overbuild than to have the thing wobble itself apart!

Sounds like you have a good plan.
Now you have to share before and after pictures!

Good luck.

[carnuck]

If you don't do an underlayer, the "sweat" from the metal roof will drip and that's all. Metal carports don't even have crossbracing except the ends and sides. Took a 70 mph blast to take mine out after 40 years, then it turned into a sail and attacked my neighbor's carport!