Tying attached garage grade beam into ICF house walls - thermal bridging
Last Post 05 Sep 2015 02:44 PM by zehboss. 8 Replies.
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GeergirlUser is Offline
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02 Sep 2015 10:44 PM
Current detail isn't ideal and will have thermal bridging - any suggestions?

Garage perimeter (where not connected to house) and slab is being poured on piles. House foundation is on piles, basement is floating slab.

Drawings are going to the engineer this week, and I'm at a loss for what other options might exist for this connection...
GeergirlUser is Offline
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02 Sep 2015 10:48 PM
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Chris JohnsonUser is Offline
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02 Sep 2015 10:56 PM
Lose the tapertop block, cut 4x4 pockets and have anchor bolts come straight out about 4-5", then 2 pcs of 2x or LVL on the flat for the top chord joists. spray foam the anchor bolts to eliminate the thermal bridging

Garage I can't see you doing too much with, perhaps ICF to the roof and insulate below the slab

Chris Johnson - Pro ICF<br>North of 49
GeergirlUser is Offline
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02 Sep 2015 11:00 PM
Hi Chris,
Not sure i understand what your suggesting...I like the tapertop for supporting the floor joists, as its my builder's preferred method for floor trusses.
Its just the garage slab that I'd prefer didn't cause a thermal bridge.
We are in extreme cold (Manitoba, Canada), and the garage will be unheated, so I don't care too much about what happens to it. Eventually (but not in the near future) we plan on insulating it.
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03 Sep 2015 01:22 AM
Why not float the garage slab and not have it connected to the house or setting on the footing at all?
Even a retired engineer can build a house successfully w/ GBT help!
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03 Sep 2015 01:18 PM
dmaceld - we were wanting to tie them together as we plan on sloping the garage floor up to the door to allow for a barrier-free wheelchair entrance. Based on our geotech, we're sitting on clay that will swell and shrink considerably, which could make the threshold significantly out-of-alignment and prohibit wheelchair use (unless we built some kind of ad-hoc ramp that would need to be adjusted regularly.)
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03 Sep 2015 05:53 PM
I wondered if something like that might not be the case. If the slab is likely to move up & down then I think you have a high probability of serious cracking if the slab is not free to float like you plan for the basement slab. Rather than fight movement, or trying to prevent it, accommodate it.

How about this idea? Put a slab segment, something like 4' x 4', physically not continuous with the floor slab, at the door tied to the footing at the door and to the floor slab at the other end. This way when the floor slab moves up and down the doorway slab will stay even with the adjoining slab at both ends.

I hope the experienced builders here will comment on the practicality of this idea. When I built my house the first concrete contractor I talked to cautioned against rebar tying exterior slabs, steps, and stoops to the foundation. The relative movement of the one with respect to the other can cause a lot of problems if you try to prevent it.


Even a retired engineer can build a house successfully w/ GBT help!
jonrUser is Offline
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04 Sep 2015 10:19 AM
I agree, slab concrete (no beams) tied at the edges isn't strong enough to resist expansion from underneath. Such expansion can come from clay changing moisture content or from freezing (underslab foam would prevent this).

Marinas have self adjusting ramps that move with 10' tides - the tiny movement being discussed should be easy; perhaps with just the flexibility of wood or steel (ie, no actual hinge).
zehbossUser is Offline
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05 Sep 2015 02:44 PM
You can use basalt rebar and re-mesh for the connection and foam a gap between them. The basalt rebar is 2.5 ish times stronger, 1/10 the thermal conductivity, and dramatically lighter to work with when available. It is also corrosion resistant and can be closer to the surface in application. It has many advantages over steel.

This will reduce the thermal bridging.

Brian
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