Basement weatherization and interior moisture management.

Please share your favorite products, ideas and links for managing basement moisture intrusion before weatherizing.  I'm not looking for info on exterior water management solutions.  I'd love to hear your thoughts.  Thanks.

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That can be difficult if you don’t address water infiltration. However if that is not of concern, then I have tried to do two things;

o provide any moisture buildup behind walls to be able to dry up through passive ventilation; air space between the foundation and wall and the bottom plate and floor. It also needs to be able to dissipate at the top of the wall to an open area or vented area.

o another way is to prevent the vapor from coming into contact with the wall by either spray foam or foiled faced H-R insulation well adhered.

In any case, and depending on the general vapor intrusion from the floor and other equipment, I would highly recommend some dehumidification. And since you know how to take care of leaks, that is a definite. But watch out for radon and other contaminants
Yo Kris:

I'm with Ewald on this subject. Just like insects, rodents and unnwanted mothers-in-law, pests (like basement H2O), only come where they are invited. And, as I'm sure you know, attacking water problems often start outside the structure. A quick Google turned up this excellent site (gotta luv those .edu sources!!)

Best wishes!
Not for nothing but if your managing basement moisture and not looking at exterior water as one of the main concerns you are not thinking the problem through properly. It all starts there, everything else is just a band-aid.
I am assuming "exterior moisture"t is already taken into consideration based on the questions. But you are absolutly correct regarding exterior water migration into buildings, but considerign teh question I was not focused on this..
If you are going to finish your basement; then you need a complete interior moisture barrier. 4 or 6 mil poly can be attached to the wall over laping and taping all seams. The poly must be continuous and extend out the floor several inches and rolled over the sill plate. Fur the wall out with pressure treated lumber and finish with moisture resistant sheet rock (MR board).
There should be no major moisture penetrating the wall causing condensation at the moisture barrier.If you have a sump pump or French drain with alot of moisture; do not finish your basement with out consulting a professional.A sump pump failure will cause a disaster.
In any case; be sure to finish the floor with below ground contact approved floor covering. Carpet, Pergo type click and lock flooring and wood products will swell or cause mold if damp, so don't use them.
I would be careful when installing a moisture barrier to the underside of the sheetrock, it can trap moisture especially on foundations since it has an exterior barrier as well 9you can trap moisture between two barriers. I have found that providing the barrier as close to the exterior basement wall as possible and allow the wall to “breath”. Trapped moisture in a abasement wall will cause mold and mildew and it can be hard to get rid of once there. Closed cell spray foam against the foundation wall may work best (moisture in a concrete wall does not worry me…it helps the concrete cure). A good source for this stuff is .
I recommended attaching the moisture barrrier, ( 4 or 6 mil poly), to the concrete wall and extending it out the floor and up over the sill plate to trap moisture against the 'concrete wall'. If I seemed to imply that it should be behind the sheetrock then I hope this clears that up. Basements in the North East only recently have started to utilize a continuous moisture proof membrane against the exterior of the foundation. Prior to that; most basements had an applied liquid coating that doesnt hold up that well. The slab under the concrete floor also needs a continuous moisture barrier. As basements are concrete block or poured masonry,(there are a few systems that utulize pressure treated wood but I hate those), moisture in contact with masonry weeps or wicks into and out. There are still building codes that don't require the membrane; as building codes are locally enforced and vary.
An interior vapor barrier (< 0.1 perm) should be used only in conjunction with some type of drainage system. Otherwise, as Ewald says, it's probably going to collect and trap moisture.

The best source for info on how to do this is Building Science Corporation, in my opinion, and they wrote a great little booklet called Read This Before You Design, Build, or Renovate with great instructions on how to do it. You can download it for free from their website. Just this week I posted an article in our blog about what we're going to do with a damp, musty basement in my condo building, and you can find the link to the BSC article there:
Agree. There should be a French Drain if the soil is wet or damp.

French Drains saved my back yards on multiple occasions!


We all know to start at the roof and work our way down to assure that bulk water is managed in the best way possible given the site conditions. Here are the resources we use when working on basement weatherization or remodeling.

When no apparent water issues are present, we have used Radon Seal to seal slabs and walls prior to finishing. This product is designed to prevent soil gases from passing through masonry. Soil gases are smaller that water vapor molecules, so it does double duty. After weatherization, we always check the radon system to make sure it is within design parameters. When making a building "tighter" one usually decreases the amount of soil gasses entering a home. Theoretically, less sub-slab depressurization is required to evacuate soil gases from the interior.

The following links you to a document from the Building Science Corp. It has served as an excellent guide for our work and should answer all of your questions.

Happy reading
Robert Post
BPI Building Analyst
i THINK WE ARE ALL MISSING THE POINT.I recommend reading 'Dry Basement Science,
what to have done and why' by Lawrence Janesky
Excerllent short book that spells out basement remodeling and water proofing for the average do it your selfer.
We have been refinishing basements for 30 years and I like this book the best for our customers.


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