Hanging open web floor trusses on ICF walls after concrete pour
New residential construction, ICF lower level with open web floor trusses supporting the main floor above – I’m stuck in the middle of a “not my problem” battle between the architect, truss fabricator and GC. Hoping someone here can offer some guidance or a suggestion or two.
We poured Nudura ICF walls long ago, and I thought we were all lined up with a truss fabricator. But something went south, and now we’re working with a new truss fabricator. Just got the truss design and am doing a final review before we pay them and they get built.
There are sections of the ICF walls where a total of 21 16″ open web floor trusses will hang on the walls, using top flange hangers (specifically MiTek TFI-416) that are nailed into a sill plate fastened to the ICF concrete core and cantilevered over the 2-5/8″ ICF interior foam. The sill plate and 10d@1-1/2″ nails offer plenty of nailing surface and allowable load to support all truss reactions, but I’m not sure what role the ICF foam plays here.
The hanger also requires 2 nails into the face, which would be through that 2-5/8″ of foam, which seems like an issue, although I have seen no info regarding forces in that direction and no evidence of others doing this.
Since the truss designer is the one who chose the hangers, I asked him whether this would actually work. He said he is not responsible for truss-to-wall connections and that I should check with the project engineer (in my case a billable contractor of the architect).
The architect said I should check with Nudura. I assume they’re going to tell me I should have used their joist hanger system, which for some reason we didn’t do. I know another option is to install a ledger, but that usually also requires some setup before concrete is poured. The GC is waiting for one of them to own up and provide some guidance. And I’m almost out of Jack Daniels.
Any suggestions for what I should do or even steps to take to get past this?
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I had a quick look at the TFI416 face mount hanger and the 2 face fasteners that are required would go into the side of your sill plate. The hanger has some additional holes that are extra and not required for typical applications - these are the triangle shaped punch outs. Is the top of your IFC wall a taper top block and designed to fully support the sill plate. If it's not, I'd be concerned about cantilevering the sill plate over 2-5/8" of foam and then hanging your floor system off this plate. That's something your engineer should look at to determine if the sill plate should be something beefier like an lvl or a 3x dimensional plate rather than typical 2x. If your sill is fully supported, you're not doing anything outside the typical install details of the mitek hanger and should be good.
Thanks for having a look, you are spot on. My project engineer suggested I call MiTek support, so I did. I just got off the phone with them and they confirmed exactly what you wrote. I was looking at the TFL, not TFI, when I got in my head the face nailing would go into the concrete, not the sill plate. All we need is 2 top and 1 face nail at each side flange, all into the sill plate, as you described.
We used tapered ICF at our basement walkout wall (where the ICF wall is merely a stem wall supporting a SIP wall). The problem wall is a retaining wall with standard, non-tapered ICF block.
MiTek said TFI-416 would work only if we scraped out the interior foam. Good thing it's only 1 side of 21 trusses, and not both sides of all 70 trusses!