Slab Insulation Detailing
bwsct
| Posted in GBA Pro Help on
I have an uninsulated, unheated 3 season room that sits on a slab we want to connect to the main part of the house. There is a 6-8 inch step down from main house to slab that we want to make even with the other parts of the house floor.
What would be the right detail to do this? Vapor barrier, rigid foam insulation and then frame the floor then subfloor? Or should we remove and created a new slab with more room To insulate?
We are in climate zone 5A in the Northeast.
Attached is a picture
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
Assuming you are leaving the existing exterior walls alone, at least from a structural standpoint. With 7-8” of build up necessary to match the main house, one option could be a floating wood slab. 2 layers of 2.5” EPS or GPS ridged board insulation, with the top layer being foil faced so the seams could be taped and edges connected to vapour retarder on the walls. Followed by 2 layers of 3/4” Advantech OSB subfloor, top layer installed perpendicular to the bottom layer, glued and screwed. This would bring you up 6.5” leaving room for finished flooring to match your existing.
https://www.greenbuildingadvisor.com/article/thermal-control-in-a-monolithic-slab
bwsct,
I second sommerbros' suggestions.