This assembly has a lot going for it! Setting the joists against the inside of the ICF foundation nearly eliminates the thermal bridging at the foundation to wall interface by taking out the rim board. The framed walls tie directly into the foundation, eliminating any extra structural tie ins often required at that transition. Another benefit to eliminating the rim is a smooth transition between the wall sheathing and the ICF foundation wall. By lapping the wall air/water barrier over the ICF wall 2-4", the wall air/water barrier can tie in seamlessly with the foundation waterproofing. Adding a capillary break beneath the footer, it is possible to tie the sub slab moisture barrier into the wall barrier without interruption.
The sill gasket (neoprene) covers the entire top of the ICF and protects the floor sheathing that lands on it. The first floor framing bottom plate is secured through the floor sheathing into the top of the concrete wall with Titan anchors.
A potential difficulty with this design is the lack of an easy path for wiring and plumbing to get from the sub floor up. The plate of the inside double wall will overhang far enough for wiring on anything greater than a 10"wall, and the use of interior wet walls, ICF sleeves and thoughtful design in the planning stages will deal with the plumbing.
Assuming a 3.25" (Amvic 3.30 ICF) ledge on the ICF the exterior assembly looks like this:
- Wall sheathing (1/2" CDX)
- Rigid foam (3" Rock wool board, poly-iso,...)
- and a 1x3 rain screen (3/4")
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