Replies

1. 
   Guest_ | Apr 17, 1999 10:10am | #1

   *
   You're a good man Ralph. Send me a sub too. They cost me $15 each issue down here.

1. 
   Guest_ | Apr 17, 1999 11:53am | #2

   *Generally, it is probably not practical to cut out web members and add new braces or purlins to compensate for the loss of structure. Trusses are engineered carefully to eliminate any excess material. It varies from case to case however if cutting something and reinforcing somewhere else will work. Depends on loads (floor, snow, roof, roof material weight), location of bearing walls below, truss depth etc. You'd need the advice and services of a structural engineer or at least a professional engineer familiar with trusses. You'd also have to find or create detailed drawings of the existing trusses. The biggest problem is a truss is normally made up of triangles only. Often the members are assumed to be loaded in tension or compression only, not bending, the joints acting like a hinge. If you eliminate even one member, it loses stability and can cause a failure. Sometimes you can create an open square area at the center of a truss, but if one side of the truss is loaded more than the other, it can cause it to become unstable and fail.A simpler way might to build a new sturdy roof frame within the roof (from outside wall to outside wall and nailed to the trusses) and then cut away parts of the trusses as needed. You'd want to nail well near the eaves so that the truss tails would continue to support the overhang. For example, you could use conventional framing with rafter and floor joists, per the span tables in the code. Provide purlins and struts and collar ties as needed.This all might be difficult to do depending on the existing wiring and ducts etc. and room available.Maybe others will have easier ways and correct me if I'm wrong.

1. 
   Guest_ | Apr 19, 1999 09:25am | #3

   *Gotta love this place Ralf,I'd say that Gary just gave you the perfect answer. He's an architect by the way, so he knows at least a little bit about structure (he quit putting the letters after his name 'cause the framers were giving him a hard time --the only letters they get are BFD and IOU). From a guy who loves to build stuff and loves math too, I'd say get an engineer to look. I bet he tells you what Gary did.DanFBI

1. 
   Guest_ | Apr 19, 1999 11:43pm | #4

   *Thanks. With the new FH software, if I input Gary Wheeler, AIA as my name, it moves the AIA to the front of my name!

1. 
   Guest_ | Apr 20, 1999 02:56am | #6

   *I'm with Gary on this one. I was a truss guy for 14 years, and was asked this question many times. Once you start cutting up the truss, it's basically worthless. You'll need to go in alongside the truss and basically frame in your own structure under the existing roof. You're talking tons of labor, as this will not be an easy job. A room addition would probably be a better idea, and might even be cheaper. Is this an option ?

2. 
   Ralph_Alvarez | Apr 20, 1999 02:56am | #5

   *
   question: I am purchasing a SW Denver tract home..built in 1980, that has prefab roof trusses. Is there any possible way to reconsonstruct
   these trusses to permit the building of an artist(small) loft in the attic.
   Your direction on where to find the answer would be most appreciated. PS I
   have given two people subscriptions to your fine magazine in the last year.