DIY Home Improvement Forum banner
1 - 4 of 4 Posts

·
Registered
Joined
·
1 Posts
Discussion Starter · #1 ·
I’m looking to finish the basement of my split level house which is in a cold climate. I have 3.5 foot high block walls in the basement that have some moisture on the walls after it rains (but never any standing water) and met with a basement contractor who recommends digging a trench out, drilling holes in the bottom of the block wall, installing drain tile and also installing a specialized product that allows the water to drain down the wall and into the drain tile. This is more or less an “insurance policy” as they guarantee the work for life. I don’t want to debate the merits of this system, but I’m looking for advice on next steps as far as vapor barrier and insulation.

The contractor’s recommendation was to apply poly against the block wall and tuck it into the lip of their system which sits along the bottom of the floor. This would create an air tight seal and allow for the water to drain into the tile. He said that no matter what they do there will likely be some moisture between the vapor barrier and block wall, but as long as the poly is sealed, that moisture is not a problem…the block can stay wet permanently without causing issues. He said I can then put 2" rigid foam right against the poly (which I’ve already bought and plan to use) for my insulation.

I asked him about the impact of using two vapor barriers, and he said its only an issue when you put poly on the block wall AND on the stud wall. This all makes sense to me but my question is does this sound okay to do? I’m okay if its overkill using the poly and then the rigid foam, I just don’t want to do something I’ll regret later. Thanks for the help.
 

·
Registered
Joined
·
37,428 Posts
Agee 110%, issue needs to be addressed from the outside.
Waterproof the foundation, grade needs to run away from the foundation, no mulch or flower beds forming ponds, working gutters with down spouts that do not just dump the water at the foundation.
 

·
Registered User
Joined
·
11,730 Posts
-----------------------------Welcome to the forums!-------------------------

So...." I don’t want to debate the merits of this system, but I’m looking for advice on next steps as far as vapor barrier and insulation."-------------- no comment.

The poly will stop all moisture from the exterior, and the foam board will keep the joint there from condensing indoor room air- but I would add the poly because; 1. Yes, two classes of vapor barrier, but as they are stacked with no wood framing/insulation between them-- no problem.

2. The foam board shrinks, creating a gap between them moisture can travel even with quality tape- another reason to poly... attach is loosely to drain condensate to the drain below, not in (my usual) 1' square glue lines to limit air/moisture; last picture in "download"; https://buildingscience.com/documents/bareports/ba-0202-basement-insulation-systems/view

Gary
 
1 - 4 of 4 Posts
Top