Hey folks. Question on roofing.
I have a "tent platform" (8' x 12' or 3 sheets of plywood) on 2 x 8 joists with 4x4 posts on all four corners (looks like a giant 4 post bed) that I want to add roofing to to make it into more of a pavillion and give it some extra rain protection. Problem is, I've never built a roof or roof trusses before.
What is the best way to go about this? Can I just build a triangle truss on each short end connected by a 12' ridge beam and start lining up my roofing on top? I'm using 8' x 3' strips of corrugated, galvanized metal roofing salvaged from a shed and carport back in FL.
How/where are your 4x4 posts attached at the bottom corners? Sunk in ground with concrete? Bottoms of 4x4s bolted to the 2x8 rim joists for the sub flooring?
Several way to go about it, IMO. Based off just the info you provided and assuming you just want some basic framing to hold the tin roofing material. I would bolt 2x6 boards around the top perimeter of the 4x4 post on the outside of the posts. Them with 2x4s I would build the basic trusses. See link below. Just the basic truss design. Guy in link does it right with glueing and screwing the gusset plates. With a 12' long span and only tin roofing on top you should be find with trusses spaced at only 24" OC providing you don't have much snow or wind loads. If you need/want a bit more strength or less chance of the trusses bowing over time or decide to roof it with 1/2" plywood and composite shingles then maybe use 2x6 material.
The trusses will sit on top of the 2x6 boards bolted to the top of the 4x4 posts. Once the trusses are in place you can run 1x4 or 2x4 across the trusses for a nailing surface for the tin rooing.
Lots of ways to do it but just depends on what kind of skill you have, load capacities your after and time you want to spend on it. Do a web image search of "home made roof truss". Also, if you are using only tin on the roof it will be quite loud when it rains.
Ummm...4x4's are set upright on cement pier blocks with 4x4 sized pockets. Floor joists are...2x8 (I think) attached to the 4x4's and to each other with 3" deck screws. At the top, the 4x4's are connected by 12' and 8' length 2x4's. I'll ad two photos here to give you a better idea. Since the photos were taken I added a ridge pole along the long side, at the center, made from a spruce tree I cut for that purpose. It's lashed,not attached with hardware. (We were putting visqueen over the ridge pole and down to the 2x4x12' runners along the top to make a makeshift roof. Now we want to add something more permanent (and waterproof lol).
The biggest problem you'll need to deal with is to get shear strength into your uprights. Any roof sitting on 4 posts will make the posts susceptible to lateral and rotational movement from snow and wind. My wood shed has a shed roof on 6 posts and the posts are walled with spaced slats on three sides of the structure. It still moves around. There's no way it would survive one season if the posts weren't tied together.
Well I was figuring on tieing them with 2x4's around the top, which will also be needed to attach the bottom of the corrugated metal roofing to as well. Won't that work?
Originally Posted by Mr. Pid
I suppose I could put in some more diagonal bracing from the post to the floor and from the post to the roof.
As Pid said you will need some type of bracing as the snow load will twist the supports and take it down.You will need some diagonal bracing.
Yeah, at this point, I'm thinking of adding a third set of 4x4 posts, in the middle (so I would have 6' from post to post along the longest side, instead of the 12' I have now, and then run 2x4's from the top of the corner posts to the bottom of the middle posts...errrr....something like that.
Originally Posted by Big Bend
I've seen a lot of pavillions with only short diag braces from about 1' down the post to about 1' out on the horizontal (bottom of the roof?) I wonder if that would work? I really want to keep it open for now, until if and when I decide to wall it in and make it a shed, at which point 16" center studs will mostly eliminate this issue.