Cut Bottom Cord of Engineered Truss

[Contraflexure74]

I've been asked to look at the following issue.

A domestic roof engineered truss has had the bottom cord cut to install an attic access hatch door. It has been cut adjacent to a node point. One truss cut only at the third point. The node gang nail at the cut point looks in distress and has partially pulled out. The adjoining trusses appear slightly out of plain. Load sharing maybe happening as plasterboard slabs are also Cracking in various locations upstairs under the truss. Cracks are less than 1mm. The upstairs internal stud walls may now be taking some roof load.

It has been like this for several years now (15 years). Should I be concerned? Any comments welcome. Anyone come across a quick economical fix option here in the past?

Engineered truss is triangular and spanning 11m at 450mm centres. 1 truss has been cut only.

 

[HouseBoy]

My experience is similar to XR's. Theoretically it is a "problem" but I don't think it is super troublesome.

I wonder ... if the access opening is important, could you reinforce the two adjacent trusses. For all the trouble you're going to (if you repair the one truss and eliminate the access there) it seems that improvement to the truss at each side should be viable.

IF YOUR QUESTION is about how to actually support the truss(s) in a way that takes the stress off so that you can install reinforcements that will actually take on the load, then I don't think it is as simple as propping up one point in the middle. My GUESS is that it would involve propping at the panel points in a manner that reverses the actual deflection better than that. (Just spit-balling here). I think I'd determine the dead load forces with a truss analysis program and then trial and error with prop forces and see how they affect those forces. Most likely a precise effort is not going to be critical but propping in multiple locations seems like the place to start.

 

[Contraflexure74]

Thanks xr250 and houseboy. Good to know you have seen this before and are not overly concerned. I like the idea of strengthening the adjoining trusses as it maybe an easier option. Would you suggest attach an additional timber to the middle third of the 2 adjoining trusses (bottom boom) and install some strong backs above the bottom booms of all trusses? Would you plywood gusset the node points of adjoining to stiffen the joints or is this overkill?