Attached garage - knee wall insulation

[liljestrom]

I have an attached garage added on and want to know options to insulate the poured frost knee wall. It is 6 inch thick and 2x6 are on top of it.
I initially told him to put a Z flashing on the outside and I'd put 2 inch foam and he can't find a Z flashing to work.
I asked him what to be done and it seems like he is running out of steam.
Like everything, I have to figure it out myself. I know I'm paying him but I'll tell you what.....If I piss him off he will walk.
I live in an area where contractors are hard to find, very hard.
I don't want to hear about the contractor....I'm telling you I've lived her for 20+ years and dealt with contractors in the past and it ***** bad.

Anyhow want ideas how to insulate this wall either from the outside or inside.
I guess one option is to put 1 inch foam on the outside and call it good or insulate from the inside with 2 inch xps and cover with some type of panel.
I dont want to build a stud wall inside.

I think my best coarse is foam on the inside with a pressure treat on bottom and a top board and put some type of panel to cover the foam.

Last attached garage I'll ever screw with.

thanks for any advice.

 

[BobnCO]

I use light gauge sheet metal 1 1/2” Z flashing on basement walls, it is sourced from Drywall Supply houses that supply contractors but they all sell retail too around here. You might go find it yourself. I’ve been a general contractor off and on my whole life, I end up holding subs hands more than you would think.

 

[BobnCO]

P.S. you can also have a local vinyl siding and or gutter company “brake” you some flashing in any of their standard prefinished colors.. white, brown, tan, etc

 

[liljestrom]

I use light gauge sheet metal 1 1/2” Z flashing on basement walls, it is sourced from Drywall Supply houses that supply contractors but they all sell retail too around here. You might go find it yourself. I’ve been a general contractor off and on my whole life, I end up holding subs hands more than you would think.

would your recommend outside or inside for the foam?

 

[The Cobbler]

in the grand scheme there's not a lot of heat loss there... I would probably glue 1" foam and tapcon 1/2 plywood over top and be happy

 

[mm08822]

in the grand scheme there's not a lot of heat loss there... I would probably glue 1" foam and tapcon 1/2 plywood over top and be happy

Since the floor is already poured and exterior back-filled, I would do as Cobbler suggests. Just prime/paint the plywood before installing so the edge resting on the floor stays protected from water/vehicle salt.

 

[BobnCO]

would your recommend outside or inside for the foam?

Either works; if you go outside with poly-iso (tolerates moisture better) you can run it below grade and gain more cold protection. Thats what I would do in Colorado.
You will get various opinions based significantly on what climate the poster lives in. (I always laugh when someone from florida or the south is advising someone in Minnesota..)

 

[duneslider]

Either works; if you go outside with poly-iso (tolerates moisture better) you can run it below grade and gain more cold protection. Thats what I would do in Colorado.
You will get various opinions based significantly on what climate the poster lives in. (I always laugh when someone from florida or the south is advising someone in Minnesota..)

I think the outside is best if you can go a foot or two below grade but it looks like it's backfilled already so unless you like digging I wouldn't go that way. I never feel like there is a great way to protect the foam on foundations either.

SO...do it on the inside and cover it with plywood. Spend extra and get the treated plywood and let it touch the concrete if you want.

For a garage I just have a hard time justifying insulating the little bit of knee wall that is showing. Maybe if you work out of it and have it heated to 70 deg all winter it makes sense but I just feel like the little bit of knee wall is nothing compared to windows and giant garage doors.

 

[MongoTA]

Wisconsin, I'd want it on the exterior. I used to live near West Bend Wisconsin, on Big Cedar Lake. Loved it up there. But insulation on the interior is better than no insulation at all. Polyiso will be a vapor barrier, XPS will be a retarder. I'd go with XPS on the interior.

If exterior XPS, try for borate-treated XPS, or as was mentioned, foil-faced polyiso is closed cell and has a foil face on both sides. Even though it's closed cell, I've seen details like wrapping the cut edges of polyiso with foil-faced aluminum tape.

You can protect the insulation with whatever cover sheathing suits your look best. Cement board, plywood, something else. Run a fat bead of urethane adhesive between the bottom edge of the insulation and the foundation, as well as between the bottom edge of the insulation and whatever sheathing you use to cover the insulation. That'll create a barrier to creepy crawley insects that might try using those protected spaces as a pathway or living area.

If using XPS and using an adhesive, make sure the adhesive is compatable with XPS. Some adhesives will dissolve XPS.

Consider bending your own flashing if you can't find it anywhere. You can buy a coil of flashing at most any store, farm and fleet or menards, or the other box stores. Cut it to a manageable length and you can bend it yourself.

Hope things work out for you.