Poly being applied to Basement walls

[Michael Larson]

Originally Posted by dvalley

Foam boards are the best method in insulating the inside of a basement studded wall.

I recommend this to all of my clients who are interested in finishing their basement. You are correct...they must be conceled under drywall. Exposed foam insulation is a no-no.

David, wouldn't this trap moisture behind the foam board the same as having poly on the wall?
What is different?

I see it both ways around here.

[David P. Valley]

Originally Posted by mlarson

David, wouldn't this trap moisture behind the foam board the same as having poly on the wall?
What is different?

I see it both ways around here.

The difference between Poly being installed on the inner side (living area side) of the studded cavity verses foam board on the outer side (against foundation) of the cavity is quite clear.

If moisture were to infiltrate a foundation consisting of Poly installed on the inner studded area, this installation would allow the foundation moisture right into the cavity and the porous studs would soak up most of the moisture and eventually rot the studs before you even realize there’s a moisture issue.

If moisture were to infiltrate a foundation with foam board installed against the foundation (leaving no cavity for migration), then the moisture will travel down the foam board and then right into the living area, which will be noticeable right away with minimum damage.

The first priority any homeowner should consider before finishing their basement is to control any moisture that may be infiltrating the foundation before they even decide to finish their basement. All foundations must be moisture resistant before attempting to finish a basement. Now that’s a whole different discussion, and I have several methods that will keep excessive moisture permanently out of your basement area.

[David P. Valley]

A simple Bump...

[John Evans]

David,

For whatever reason, virtually all newer homes with basements in our area have the interior foundation walls covered from sill to the floor with foil faced fiberglass insulation nailed to the walls. I have noted damp to wet insulation on a number of these homes. Of course, it is rather difficult to actually inspect for moisture, especially with the foil. Have also seen installation of finished drywall stud walls placed against the foil insulation.

Question about the foam board installation, should the board be attached to the exterior side of the framed walls before they are set, leaving an air gap between the foundation walls and the framed walls?

[David P. Valley]

Originally Posted by jevans

David,

For whatever reason, virtually all newer homes with basements in our area have the interior foundation walls covered from sill to the floor with foil faced fiberglass insulation nailed to the walls. I have noted damp to wet insulation on a number of these homes. Of course, it is rather difficult to actually inspect for moisture, especially with the foil. Have also seen installation of finished drywall stud walls placed against the foil insulation.

Question about the foam board installation, should the board be attached to the exterior side of the framed walls before they are set, leaving an air gap between the foundation walls and the framed walls?

Before any wall material is installed on any foundation, it must be a dry basement.

If I were to install rigid board foam insulation boards on a dry foundation, I'd do it this way.

[Peter C. Russell]

Dave, all of the basements I have finished I have done with the foam against the foundation, Instead of using strapping I use 2X4s insulated with fiberglass and then drywalled.

[David P. Valley]

Originally Posted by prussell

Dave, all of the basements I have finished I have done with the foam against the foundation, Instead of using strapping I use 2X4s insulated with fiberglass and then drywalled.

Aren't choices wonderful?

[Patrick Bolliger]

Ya mean like this Dave...

Finished basement, Possible batts fiberglass and maybe some poly or plastic behind drywall....

Inside mechanical closet behind water heater/ furnace.

EIFS with vinyl siding "SEALED" to stone veneer base exterior. NO drainage possible..
The morons who put this place together should get "idiot of the year" award.

[Marcel R. Cyr]

Originally Posted by dvalley

Before any wall material is installed on any foundation, it must be a dry basement.

If I were to install rigid board foam insulation boards on a dry foundation, I'd do it this way.

Right choice on both counts David.
I am a strong believer in polystyrene foam board in a basement in lieu of fiberglass.
Vapor barrier in basement. Ouch, open it up in a few years and you will see why.
Concrete foundations are full of moisture and need to breathe and dry out, and since they can't dry out towards the outside obviously, they need to let this moisture out towards the inside.
Now add a moisture barrier or retarder on the inside of your studs and it is trapped in the cavity. Fiberglass will render it's r-factor useless and moisture will eventually creep to the floor level.

The video that you showed is quite new where it is rabbeted for the thickness of the strapping. I am used to using z-girts out of metal, and never like it due it's thermal bridging.
They only thing I did not see in the video is the attachment of the strapping, using powder actuated fasteners with Styrofoam is a no no.
Tap-cons? They were using a battery drill with masonry screws, wow, wish I could find those screws that I don't need to drill with a hammer drill.

[David P. Valley]

Originally Posted by mcyr

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They were using a battery drill with masonry screws, wow, wish I could find those screws that I don't need to drill with a hammer drill.

Marcel,

When has an advertising agency ever advertised the real deal? Everything advertised today is fluffed or rigged so the consumers are placed in awe. They obviously want consumers running to the store to purchase their product.

[Kenton H. Shepard, CMI]

Originally Posted by dvalley

Yep. I'm simply going to red flag all those vapor barrier installs one home at a time.

I don't care what the other now-it-alls say about this foolish barrier, vapor barriers cause Mold build-up. I've seen it with my own eyes...

Vapor barriers are the Yugo of building design.