Latex paint on fieldstone foundation
Hi,
I’m a new homebuyer, and know little about building science other than what I’ve been able to glean from this blog (thank you!). I’m in the process of buying a house in the northeast that has a fieldstone foundation. When I first saw and put an offer on the house, the basement walls looked fine, but since the weather has been warming, there is evidence of moisture coming through (although it is not clear how much), and most recently, some mold. As it turns out, the seller painted the interior basement walls with a latex paint, which, I have learned, is essentially mold food. I’m now trying to figure out how the basement can be salvaged, without creating a lot of mold.
I had Basement Systems come out, and they recommended installing sheets of polyethylene over the walls to encapsulate them (and channel water to a perimeter drain and sump pump, which they would install). I know how little I know about this stuff, but this suggestion seems crazy to me. You may cover one side of the walls, but it seems to me you’ll be creating an ideal area for mold behind the polyethylene, and it could very well propagate upwards into the walls of the house. Am I wrong about this?
The seller suggested simply spraying closed-cell spray foam over the walls (with the latex paint underneath). I’m concerned that the water will keep coming, dislodge the latex paint, and with it the spray foam. Does this seem like a good solution?
The other option is trying to get the latex paint off the walls, and after that’s done, simply installing a dehumidifier. But the seller is balking at the difficulty of removing the paint from the fieldstone.
Any hints anyone has will be very greatly appreciated.
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Replies
Lucas,
The advice you have been given isn't bad.
Your solution will depend on your budget. For an overview of all the problems you may need to address, see this article: Fixing a Wet Basement.
By the way, stop worrying about the latex paint. It's irrelevant.
Assuming that you have an adequate budget, that the exterior grade slopes away from the house, and that the stonework is structurally solid (without loose stones), here's the best approach:
1. Install an interior French drain, a sump, and a sump pump.
2. Drape a waterproof membrane onto the interior side of the stone walls. Polyethylene would work, but an EPDM roofing membrane would be more durable. This membrane should direct water to the French drain.
3. Install an adequate layer of closed-cell spray foam on the interior side of the membrane.
4. Protect the cured spray foam with gypsum drywall (installed on studs, of course) or an intumescent coating.
Here is a link to an article with more information: Rubble Foundations.
Martin,
Thanks so much for this answer--and for calming me down about the latex paint. I'm a little doubtful that the seller is going to go for all of that, since (given the quote I got yesterday) it seems likely to run towards the $20,000 range, and since the house inspector thought that a perimeter drain and sump pump was "overkill" for that basement. I understand that you're offering the best solution, but can I also ask you for a more minimal solution as well? That is, would it be ok to only apply the spray foam directly to the painted wall? Could a french drain be added later, if necessary? Or would it have to be done before the spray foam?
Thanks so much again. I never learned anything about this stuff previously--but am doing my best to learn now.
Lucas,
What you decide to do depends on what you intend to do with your basement, and with how damp things are now.
Do you intend to turn it into living space? If so, it has to be impeccably dry before you move forward with your plans.
Is it just an old-fashioned cellar with a furnace and a water heater on concrete blocks? If so, maybe everything is just fine the way it is.
Does anyone in your family have an allergy to mold? Then I suppose you want a mold-free house.
Lots of issues here -- only you can decide what you want.
It's hard to tell from your description whether this is a really wet basement, or just a pretty good basement with a touch of mold.
If you don't have any puddles or big issues down there, other than a musty smell, you may be happy living in the home the way it is for the next 50 years.
Before moving into my new house, I rented a house with fieldstone foundation (uninsulated, etc) for many years. It was on beautiful property, but the basement was not in good shape, there was even a small "stream" that would appear during times of heavy precipitation.
Depending on the condition of your (potential) fieldstone foundation and your goals/budget, you may have to perform the work mentioned by Martin combined with exterior excavation and water management work.
Keep in mind, it's been a low snow year with below normal precipitation for most of the Northeast, you may be seeing best case spring basement conditions right now.
If this property/house has lots of other redeeming qualities and you have the budget to deal with the foundation, great. If not, I'd honestly pause and make sure this purchase makes sense for you.
Sorry to be an alarmist and maybe the foundation you're looking at is in good shape and/or worth dealing with, but wanted to pass along my experience.
Martin,
Thanks for being so generous with your time. It will be basically a storage space, laundry space, mechanicals space--not a living space. I do have mold allergies, and so have been quite worried to see new mold developing on the walls over the last week, after a pretty heavy rain.
The house inspector said it was hard to tell the amount of water coming through the walls because of the paint. But there is dampness on the walls and in the air of the basement--none at this point on the ground. It is quite dry now in CT in general (historically), so I could imagine it getting somewhat worse. But work needs to be done on the outside of the house too (grading, gutters), and so that may mitigate the problem.
The seller owns a spray foam company, and that's why that issue has been mentioned. I assume it's relatively easy/cheap for him to do.
Thanks again.
Lucas,
Water can trickle through the stonework, so just closed-cell spray foam (without the rubber membrane) will work. You may still end up needing a French drain at the base of the wall, though.
Negotiate hard; make it clear that the mold is a deal-breaker, and insist on the spray foam. Contact the local code authority to determine what type of fire protection is required on the interior side of the spray foam in this jurisdiction. See if you can get a reduction in the sales price because the foundation is defective.
Martin,
Thanks. Just to be sure I'm clear--even though water can trickle through the stonework, closed-cell spray foam (without the rubber membrane) sprayed directly on the interior of the painted stone wall will work, right? Can the french drain be installed after the spray foam, if necessary, or does it have to be done first?
Thank you again.
Lucas,
There are advantages and disadvantages to both approaches (with and without the membrane).
If the closed-cell spray foam is sprayed directly on the stones, it can provide structural reinforcement. That's good.
In theory, there will be an easier path for water to get to the bottom of the wall if you include a membrane. If you decide that you prefer to have a membrane, polyethylene is cheap, so you could always include the poly.
At the base of the wall, it wouldn't hurt to install a 4-inch-wide strip of dimple mat (the type of dimple mat usually installed on the exterior of a foundation wall) before the foam is sprayed -- that will provide a path for any liquid water. If you do that, the French drain could be installed later.