Assembly Critique: Floor btwn Garage & Living Space
paulmagnuscalabro
| Posted in General Questions on
Hi All,
Will this assembly work for a floor separating an occasionally-heated garage/shop space from living space?
CZ6, southwest Montana
See attached PDF for floor assembly.
CZ6, southwest Montana
See attached PDF for floor assembly.
Parameters:
– Existing garage/shop outbuilding
– Garage bay to be wood shop, insulated, heated occasionally by an NG heater
– Other bay & entire upper level to be conditioned living space.
– Other bay & entire upper level to be conditioned living space.
– Wall between shop & living space on main level basically an exterior wall, with “exterior” insulation on the shop side.
– Self-performing the work.
– Self-performing the work.
Assembly from top (conditioned) to bottom (unconditioned):
– 2×6 T&G flooring, over
– 2×8 rough sawn floor joists @ 24″ O.C.
In between the joists:
– ±4″ of fluffy insulation, over
– 2x layers of 1 1/2″ rigid insulation (NGX readily available), cut-‘n-cobbled between joist bays, canned spray foam to seal the edges between foam and joist, staggered seams also foamed
Below joists:
– 2×4 strapping perpendicular to joists at 16″ o.c., with 1 1/2″ rigid between strapping.
– 5/8″ Gyp, fire taped
– 3/4″ ply finished ceiling
– Electrical/lighting in conduit below/attached to ply
Thanks,
Paul
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Replies
Based on this article, seems like I'll be okay with the above assembly:
https://www.greenbuildingadvisor.com/article/insulating-a-wood-framed-floor-assembly
Anyone else have any thoughts / suggestions?
Giving this one more shot, simplified post above
I would forgo cut and cobble and make your air seal lower down, at your furring strips and the foam in between, using tape. I think your cut and cobble is going to create a bunch of little micro climates within the assembly that will have difficulty drying in either direction. I would also probably just use fluffy stuff in joist area.
alternatively, if you are just trying to create an air barrier, just use a membrane like intello, especially if garage is insulated and heated.
Thanks Freyr. I guess now that I think about it - if I'm not planning to have any drywall penetrations (other than fasteners), would using Drywall as the primary air barrier be adequate?
So top-down it'd look like:
- 2x6 flooring, over
- 2x8 framing w/ fluffy insulation, over
- 2x6 perpendicular strapping w/ rigid between, over
- 5/8 drywall, fire taped and air sealed at perimeter, over
- 3/4 ply finished ceiling
Although... taping the lowest NGX/strapping seam sounds way easier. Great suggestion.
Ya just make sure you detail at your top plate, usually you will lay a piece of air barrier to tie in with Sheetrock and exterior sheathing (if that’s your air barrier). Something like Henry vp100 that is SA works well on top of garage top plate and under FJ. You can then add a strip of ply of top to protect it during Floor joist install ( or just be careful).
Actually now thinking about it you could put that in between double top plate as your are furring down.