convert to trusses, in place

I have an 18'W x 26'L workshop with a standard rafter/joist type roof 24" oc, with loadbearing poles down the middle. I'd like to convert the roof supports (in place) to a truss-type design so that I can remove all the center poles. Can you point me to a book(s) or other source of information that will show me how to calculate the load that is currently being supported and how to convert the current supports to a truss that will support that load?

 

You will not find such a conversion book. What you might do is first go to your local building dept, and find out what the roof load code for your area is. I probably would not tell them what your going to do. Just get the info. Then go to a home improvement center that sells 18' trusses with the pitch you want, and measure one of the trusses. You will have to get gang nail plates, lots of them probably at least 12 for each one, and then go from there.
This is not an easy job, and I am not sure your gain would benefit all the work and cost. Good Luck

 

It would be faster to tear off the existing roof, rafters, and joists, and replace them eith the new trusses.

 

I agree with MTAC, and, if your time is worth anything, cheaper too. You will spend a LOT of extra time trying to do this with the roof in place, and teach all that lumber a whole new vocabulary!

 

Both Lefty and Carpenter are correct, and that is what I would do also, however, I did not mention it, because that was not the question you asked. Good Luck.

 

Well, I never would've guessed that it would be easier to pull the old roof off rather than to convert to trusses in place. But then, I've never really seen a truss up close. I'm not sure if an 18' truss would be made of 2x8 ... 2x10 ... stock ?? I've seen designs for Pratt web, W-type and King-post trusses and it looked as though a good chop saw, a dozen nail plates each and a nail gun would make for a fairly quick conversion(not necessarily easy, but I don't mind moderately-hard labor). I guess I'll start with the first suggestion and check out local load codes and take an up-close-and-personal look at trusses in a local yard. Thanks for your input, guys.

 

What size of lumber the trusses will be made of will be determined by a combination of span and load they will be supporting, or expected to support. With only an 18' span, I would expect to see my trusses made with either 2X4's or 2X6', unless, of course, you live in an area with a high snow load or wind load requirement, want to install a tile roof on them, or both!