coop roof

[monipit]

I have an old chicken coop that has a roof in need of repair. The main (and only) load baring beam is cracked and partially separated at two spots where there are posts supporting the beam. The posts are only rusted out metal pipes put there years ago.
I plan on sistering new 2x12's (not sure of the length of beam, its 20-30' long) to the original main beam boards with nut and bolts. Then use pressure treated 4x4's (heavy enough?) as posts to support the beam (concrete floor). The coop is 20-30' long and about 15' wide, how far apart should the posts be placed. The beam is centered down the length, the rafters look like 2x6's. Are 2x6's heavy enough, and how far apart should they be (right now they are maybe 20" apart)?
Am new at this, so any help is greatly appreciated.

[HayZee518]

so from what I've read, the side walls are falling down? the run length? why would there be boards mounted up-down not flat like an upper plate?

[monipit]

No, the walls are in good shape and the top plate of the wall is good also. The beam running the length of the building has cracked in two places where the previous owner (builder?) only had two metal pipes holding up the whole run of 20-30'.
There are boards laying across the top plate (15') which make up the original roof. At some point plywood was added on top of that, then covered with tar paper.
Th main problem is the roof has a belly due to the cracked beam and needs to be shored up. I think my idea will fix it. I am just wondering if the size of the posts and the rafters will be alright. If you have any other ideas, I'd appreciate the help.

[WVslottech]

your ideas will work fine bud. 2x6 will be enough. put them 16" oc.
4x4 posts will work also. this may help you also, ramset a 6" piece of PT lumber to your floor, then set and attach your support posts to that. replacing the 2 steel lolly cloumns with your 4x4s will be good enough. believe me...ive seen some house roofs that were supported with less, and you'd look at it and say " how it's that not down around their ears! LOL. Good Luck

[monipit]

Thanks for your reply WVslottech, I was starting to think my post was going to die unanswered. Thought I didn't explain it well enough. Good to know my ideas will work, and I'll use your tip also.
Any suggestions on how many support posts to use? Right now there are only the two, each in about 10' from the wall (dividing the non supported area into three 10' sections). Again, hope I'm explaining it right.

[WVslottech]

be honest with you, after you shore up with the sistering...2 would work. that's whats there now right? but if you wanted to divide it up, and add a 3rd, it wouldn't hurt a thing . also...you really don't need to sister the beam with bolts. save some money, and use a consruction adhesive (Liquid nails) when you sister on your 2x12's, and blast some 16 penny ring shanks in it. you'll be supprised how much that's gonna stiffen it up for ya! need anything else holler...i'm here for a while, fell off a scaffold the other day at work LOL...so all I have to stay busy for a few days is this PC!!! Later Bro

[monipit]

Sorry about your accident. I'll get the adhesive and the ring shanks. Thanks again for your help.