Shim between steel beam and wood joists 2

[milkshakelake]

I'm adding a steel beam under the 2/3rd span of existing joists, since the joists fail without the beam. These are my details below. The issue: the joists are not level, so some of them need shims. How do I install these shims? I'm mostly worried about nailing between the joist, shim, and sill plate runner.

I normally say "shim as required." But the contractor said he needs a good shim detail. When the contractor doesn't want to cut corners, I'm always going to help.

 

[jerseyshore]

Are they looking to level or jack up the joists or just stabilize in place?

 

[phamENG]

I'd have them cut 1-1/2" shims and insert from both sides as far as is needed to provide full bearing. Then nail it off as they normally would. Nothing special is needed, really.

 

[milkshakelake]

@jerseyshore Just stabilize in place.

@phamENG Got it, will do. That's a pretty simple solution.

 

[GC_Hopi]

You could also look at sistering on squash blocks on either side of the joist. Glue and nail them off and lower them as needed to bear on the new beam

 

[milkshakelake]

I think shimming is easier, but thanks for the suggestion!

 

[kipfoot]

You might also add a note about what to do for bigger gaps. Off-the-shelf shims are maybe 1/4" at the thick end. If the joists are wonky you might need something thicker. If you don't want them to add multiple pieces, which starts to look sloppy, you could add a note to cut a flat block to add in addition to wedge shims.

It probably works either way, so the biggest benefit may be that the contractor will feel that he made a request and that you thought it through.

 

[XR250]

You can also nail a short 2x6 stiffknee vertically to the side of the joist to make up the gap.

 

[lexpatrie]

Blocking should show as [\] not [X] as it isn't continuous through the depth of the cross-section.

The shim is intended to go into bearing isn't it? If they drive it in with a hammer, say, won't it stay in place via friction unless moisture/thermal changes things? It could be nailed in, or glued, if desired I suppose. If the shim is at least as wide as the joist and of similar species, the crushing "strength" should be similar.

Are you considering that beam braced on the top flange by that connection the joist?

 

[milkshakelake]

@kipfoot I did consider that most shims are pretty small. I'll add a note that if it's larger, they'll have to cut out a block. I don't want them to add multiple pieces for sure!

@XR250 GC_Hopi had the same suggestion. I think shims are easier. Thanks for the perspective!

@lexpatrie I didn't know about not using an X, that's something new to me. Will look into that. Yes, hammering in from the side will turn it into a friction connection, which is unreliable. I will specify some nailing. I'm not a big fan of glue (more of a lack of knowledge than anything). Yes, I am considering the beam top flange to be braced by the joist.

 

[lexpatrie]

If the steel is being braced by the wood above, there needs to be an explicit (mechanical) connection. What do you think about like a Simpson STC connector for that? I think those are rated for some lateral load and allow some up-down movement (i.e. tolerance for the shims?).

Alternately I'd look at the span, because sometimes these steel in wood structures the unbraced length is not all that influential. Especially if the steel is "column-like" i.e. W8. I don't normally need Lp or less, is what I mean, as the steel doesn't need to achieve the full Mp.

 

[Tomfh]

I just did a shim job at my house. I used the nylon shims they use for supporting precast panels. They’re pretty strong and you can hammer them into the gaps, plus a bit of sikaflex, in the off chance they come loose. You could fasten it too if you’re worried. Fibre cement sheeting works well too, but often requires a slight lift of the joist before it goes in. You cant hammer it like you can a nylon block.

 

[milkshakelake]

@lexpatrie I don't think there needs to be an explicit mechanical connection, because nails through the shims can provide that. But anyway, I will check lateral torsional buckling. Thanks for picking that up. I don't think it will control, but it's always good to check.

@Tomfh I'd need to have nails penetrate it though, to get a good connection. I wouldn't want to just rely on Sikaflex and friction. I've never used them before but if they're really hard, a nail might not penetrate.

 

[lexpatrie]

If the span and the load are low enough the beam could be fine without a stabilizing/bracing connection from the wood above. But if you're designing it for a braced length that's less than the span, then there should be a designed connection to resist buckling out of plane (LTB, inelastic LTB, depending on the Lb).