working on new tractor shed question

Have the foundation and 4 ft concrete walls in place from an old hoghouse. Found 8 used rafters in good shape reasonable. Problem is..shed foundation is 60 ft long and there are 8 rafters. Is that going to be enough in Iowa? I already have most of the tin I salvaged off the hog building(the roof blew off the hog building-it was a monoslope without enough head room for anything) And I also salvaged about 50 12 ft 2x8s..

Probably not. 50 pounds/sqft. is probable load. (I assume you have trusses, not rafters) trusses look like a bridge, rafters are plain dimension lumber like your 2X8s.
The span of the walls is critical. If you are 24' wide, you will need engineered trusses on 24" centers (probably) if narrower, they can be somewhat farther apart, supporting the girts for the roofing. Your best bet is to discuss this with the local construction trade school for a recommendation.
Duplicating your trusses to make enough to do the job is probably best, and least expensive. You may have 1/3 of the required parts. Jim

Most pole barns here are 7.6' or 8' on center for rafters.

http://cedarrapids.craigslist.org/bfs/4041887808.html

these are what I found.

and the building is 36 ft wide. forgot to add that

You are going to have to find out what those particular rafters were engineered for. Ask then what the center was?

I am Mount Vernon, where are you?

they look like trusses. Bill
rafters on craigslist

I am 15 miles north of dyersville

You must know Pat's repair, he does my blasting and priming.

I know where it is..havent done any business there.

Waaaay too little info. Details on rafter construction? 2x 6-8-10? Bracing? Lower chord?

Those look very like trusses to me and if you build up your gables with blocks or bricks you will have more than enough trusses. We are not in the same situation as you but over here we work with 15 foot (or 15' 9"...The metric equivilent!) centres and use 7x4s as runners. All our sheds even with a much flatter pitch are done that way and ...Yes, we do get heavy wet snow from time to time.
Have a look around some other sheds in your area and take some advice from a local builder.
Enjoy you tractor shed and I hope you get rid of the pig smell!!
Sam

I can't imagine putting them more than two feet apart which means you will need 22 more trusses. I helped on a project once where the guy built them himself. He got everything laid out on the deck, and then nailed pieces of 2x4 down to the deck to serve as a jig for placing all the parts. The plates for the joints were cut out of 1/2 plywood. Forty eight years later it has seen a lot of snow and is still standing. You could do the same thing on a piece of level ground using 10 inch dirt nails to hold your jig pieces.

Trusses are about the top board and bottom chord being able to spread the weight of a full load of snow and wind between them. The top board wants to bend down and compress a bit, and the bottom chord wants to pull apart.

They get ratings from their manufaturer.

Either you follow these ratings, or you get them cheap and way way overbuild......

Are you going to build the special end trusses yourself, or just use one of these for each end? Typically the end ones are built differently.

So you have 60 feet, if you make the 2 end trusses, these 8 could be spaced every 6 feet.

That might work. They do not have a real strong bottom chord, but might work.

If you are trying to use these 8 spaced out including the 2 ends, that puts them at 7.5 feet.

Boy, just eyeballing it, they look weak for a near 8 foot span.

My 48 by 81 shed was built with 9 feet between the trusses, but there is a 'lot' more beef on the chords.....

It is all an engineering game, size of the wood, the number of braces in each truss, the way they attach to the wall, and so on. An engineer can figure out what you have, but your point was to be cheap which I respect very much, just you need to overbuild then, not try to get by on the edge of what they will take......

House trusses are built for 16 or 24 inch spacing, I hope that isn't what you got...... Those are smallish chords on the picture... Since you won't have the live load a house does, you could stretch them a little more, but not to 6 or 8 feet!

Paul

I dont have them yet..am trying to get hold of my civil engineer bil...thought id ask here first..

A thirty eight foot truss and a thirty six foot building will not match up. A truss has load bearing points . You need a truss that is designed to sit on a thirty six foot building. That alone will make those trusses unfit for that particular use.

Those are "M" trusses. They need to be spaced no more than 3 feet (opinion, not fact) THey could be used on a smaller span by putting in a load post at the point they touch the top plate or ledger of the walls. The post should go between the bottom chord and the top chord on each end to accommodate the load transfer to the strength of the truss. It will increase the sofit (overhang)
I would just have the roof engineered correctly rather than compromising with these. Jim

It looks like he has remnants of a house gable. Those trusses were most likely designed for 2' centers or less. You can see the members are 2x4 stock. In contrast the trusses on my dads garage with a 30' span and 10' spacing are 2x6 members. If you need the roof to "pass" in Iowa, you should involve a structural engineer, especially when you are trying to re-use an engineered product like wood trusses.