Modified Truss Heel

[StrEng007]

Does anyone know of any technical data for "re-heeling an existing truss"?

More specifically, the analysis process for removing the existing bearing of an existing truss and providing a new hanger support. The procedure would be as follows:

1. Shore truss,
2. Cut back overhang and bearing so the new end of truss is flush with interior wall (at concrete/masonry) or ledger etc.
3. Provide plywood sheathing each side to reinforce end of new truss heel.
4. Rehang the truss with new hanger.

I'm already familiar with the theoretical approach to reinforcing the web members with plywood sheathing.
My real concern here is how this modification can inadvertently change the stiffness of the truss or create propensity for additional deflection.

 

[XR250]

Honestly, for most, I use 24" long, 3/4"plywood on each side (allows the use of a standard 3" wide hanger) with a enough fasteners to resist the top chord thrust/bottom chord tension and then call it a day. I also add glue for giggles.
If it is a raised heel truss, the diagonal web needs to be fastened adequately as well.

 

[KootK]

My real concern here is how this modification can inadvertently change the stiffness of the truss or create propensity for additional deflection.

Much depends on the truss geometry, before and after. Can you share that with us?

Many common truss heels are predominantly arch ties. When that's the case, a little slip at the heel probably doesn't translate into all that much mid-span deflection. This is also a fine reason do glue in addition to fasten as XR250 mentioned. Hopefully, in service, the glue holds and there really is not any fastener slip.

For common trusses without raised heel, I like to mimic the sliders that the truss design software will include in such situations. And for the same reason: most common truss heel joints do not come together concentrically at the heel. In shortening the truss, you've likely made that worse to some degree.