How to Maintain a Stone Foundation
LESLIE: Mike in Missouri, you’ve got The Money Pit. How can we help you today?
MIKE: Yes. I have an 1873 home with a stone foundation.
MIKE: And the stone’s in very good shape but it keeps crumbing: a light, sand deterioration onto the floors on the inside. And I was trying – I would like to slow that or stop it without – I have read that stone foundations should be allowed to breathe and it’s survived very well for 140 years.
TOM: Yeah. But I mean let’s – enough already. It’s 140 years; you’ve got to maintain this at this point in time.
MIKE: Yes, yes.
TOM: What’s happening is the mortar in between the stones is deteriorating and it has to be repointed. So you’re explaining a very normal condition where the mortar eventually dries out after 140 years and needs to be taken out and repointed.
So, typically, this is a job done by a mason. They mix up a very sticky mix of mortar, usually with a lot of – extra amount of lime in it to make it stick. And they pull out the loose mortar and then repoint it: press new mortar into place. And that’s the way you maintain a floor like that.
I don’t know what “breathing” has to do with it. Foundations are foundations; you want to keep the moisture away from them on the outside of your house. But when the mortar starts to deteriorate like that, it’s got to be pulled out and repointed.
MIKE: I see. So it’s more mortar deterioration than the stone.
TOM: Than the stone itself, that’s correct. Yep.
TOM: Stone’s going to last forever; it’s the mortar that needs some work.
MIKE: OK. And then one other quick question. Two of the floors have – by a previous owner were Puritan pavers. And moisture – ground moisture – sometimes leaches up through. Do I need to take all the pavers out and put a plastic under them or what?
TOM: Well, if you’ve got water that’s leaking up from the floor of the basement, that points to poor drainage conditions. And so what’s going on here is simply that you have moisture that’s collecting at the foundation perimeter and it needs to be drained away from the foundation further, because that water collecting outside your house pushes down along the foundation wall. I’m sure it goes through the wall. You may be seeing some efflorescence because of the deteriorated moisture – the deteriorated mortar that you have – and then it eventually comes up under the floor.
So I need you to look at gutters – making sure they’re clean, free-flowing and extended 4 to 6 feet from the house – and grading, making sure the soil is sloped in such a way that water runs away from the house. Those two things should stop or completely stop that water that’s rising up in the basement floor.
MIKE: Yes. And I know you’re right. This entire town has drainage problems and so even the ditches out at the edge of town – it’s a rural area. Even the ditches don’t drain away very well.
TOM: Yeah. But you know what? You don’t have to worry about the entire town; you have to worry about the first 4 to 6 feet around your foundation and that’ll do it.
MIKE: Thank you.
TOM: Good luck with that project. Thanks so much for calling us at 888-MONEY-PIT.