Floor truss questions

I recently had 2 home withing 2 weeks that had engineer trusses. The worst one was yesterdays inspection. The trusses had no supports and spanned about 30 ft on 16" centers.

Does anyone know ft for ft how much more a truss can span over a typical joist. obviously the span was too far, because the home settled to the center from both ends. No level soup at this dining room table.

Trusses can span over extended distances depending on their design and size.

It really depends, as you can see here:


It is important to note your findings though.

I guess since the house was sinking in the middle would be an indication that somthing was wrong :mrgreen:. I don’t get it 2nd home in two weeks that the trusses were settling. the first was just a wavy floor on a small home. the buyers were not too concerned, but yesterdays was obviously an issue.

I have had personal experience with engineered trusses spanning 30 feet, they SAY they can hold the weight, my experience says they sag. It didnt help that in the middle of the floor there was a fireplace insert. It cracked the drywall every year above the fireplace.

I had the same experience, Michael…poor design.

30 feet is no problem for a properly designed truss system. If there is excessive deflection, the design was improper or the system was overloaded - it’s just that simple.

They make Bridges out of Trusses and they seem to be doing OK…:smiley:

Also, foundation dont sink because of an improper floor design but rather weak soil under the footings.

Code typically allow spans with a deflection of L/360…however its best for a builder to go with the at least L/420 or better… other wise you run into all sorts of problems.

Truss engineers have thier own idea of what is acceptable. Deflection is designed into the truss and is stated in the truss calcs. I have seen hip roof trusses with one truss having 1 3/4" deflection next to one having 3/4" deflection. Engineer thinks it is good, but the ceiling looks like crap! As far as floor trusses, watch out for upside down, guaranteed to sag.