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Community and Q&A

Door threshhold detail at slab on grade “porch”

Archi_Jules | Posted in Energy Efficiency and Durability on

I am drawing up a bunkhouse with a concrete slab on grade porch along the front of the building. The bunkhouse has a poured concrete basement and we need to meet energy code insulation for Zone 5. So we are planning to use 3 inches of continuous Rigid Insulation at the exterior of the basement walls to meet R-15. The basement is just for mechanical and storage so we don’t want to go to the expense of having interior furred walls with insulation on the interior.

The wall section would be somewhat similar to Detail 1-05011 on this site (which shows 4 inches Rigid). Also similar to this detail, we are offsetting the wall above from the foundation by 2 inches – however, we are bringing the concrete foundation wall up to meet the stud wall – and notching it on the interior side so the truss sits on the lower notch. The concrete porch slab will then abut the 3 inches of insulation – and we can dowel across the insulation into the foundation wall – so says my structural engineer.

My question is what to do at the door thresholds where we’ll now have a 3 inch exposure of insulation. How does one detail a good threshhold  to cover this?

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  1. maine_tyler | | #1

    It's tough to picture this situation exactly (and searching the detail library by number appears not to be an option).

    It sounds like you have to bridge the foam. I wonder if reducing from 3 inches in that one spot (with a tapered pour?) would assist.
    And/or how about a stone sill extension to span over the foam? Will the porch be a touch lower allowing for a slope in the sill, hopefully?

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