Nasty mold problem in basement...

[RedTartan]

I need ideas on how to fix a mold problem in my basement. This is not the deadly black mold, it's actually kind of white and fuzzy looking. Ordinarily I just wash mold off with bleach water, but that's going to be problematic considering where this mold is.

My house is really old. The basement walls are made of large, rounded stones mortared together. A previous owner PAINTED my lovely rock walls and now there is mold growing under/in the paint causing the paint to bubble up and look horrible. I can't pressure wash the walls because I think it would blow out the mortar.

Could I just scrape off the paint bubbles, spray with bleach water to get most of the mold, and then repaint with Kilz or something? I'm getting a dehumidifier to fix the moisture problem.

I swear it should be against the law to paint bare stone and wood...

RedTartan

[longrider]

I used a garden pressure sprayer ( 2 gallon ) filled with water and some clorox. just pumped it up and sprayed everything very good.

if it got there once it will get there again. might need better ventilation. On fishing yachts most owners leave one occillation fan below decks to keep the air moving and drying.

in ours we put a fan and dehumidifier down there to help, ran the drain line outside.

[meanwhile]

Try good air flow too. We had trouble in our basement and solved it, mostly, with fans. We set one fan to blow into and area, and a 2nd one to suck air out. We used those fans for a whole summer but only on days it was DRY! Close the doors back up when raining. The air flow helped more than any clorox to dry up mold and bad smells. Then I had the Heat/Ac man cut a hole into a main trunk line, and put an air vent down there. BUT! We keep it closed up almost all the way. That air is enough to help dry things out. We still put fans down there and leave one on low when it seems to be damp again.

Good luck - it is a challenging problem.

[cfabe]

White and fuzzy sounds more like effloresence than mold. Efflorescent is a deposit left when minerals in the cement/mortar leach out because of dampness moving from the ground into the basement. Eventually this will weaken the mortar. If your mortar is in such bad shape that you think pressure washing it would blow it out, it is probably time for it to be replaced.

[celticfarmgal]

when you repaint you need to use drylock it is specifically formulated to "lock out moisture"

[BethW]

Originally Posted by celticfarmgal

when you repaint you need to use drylock it is specifically formulated to "lock out moisture"

Products that claim to lock out moisture also lock IN moisture. Water vapor needs a way to escape, especially in old houses with antique mortar.

Redtartan, there's a place here in VA that specializes in old mortars and masonry. They're also great about fielding calls for advice. You might want to check them out: www.virginialimeworks.com.

[Watcher48]

You need to go in and pressure wash the rock, take the paint off, tuck point all the bad mortar and then put a dehumidifier down there. Not the simple solution you were looking for sorry

[RedTartan]

Originally Posted by cfabe

White and fuzzy sounds more like effloresence than mold. Efflorescent is a deposit left when minerals in the cement/mortar leach out because of dampness moving from the ground into the basement. Eventually this will weaken the mortar. If your mortar is in such bad shape that you think pressure washing it would blow it out, it is probably time for it to be replaced.

I think you're right. I went down and scraped some of the paint off and I don't think it's mold anymore. How can I repair the mortar? The mortar right now looks like sandy dirt. Do I just dig out some of it and put in new stuff? My walls are more than a foot thick, probably closer to 18". Maybe I should just pressure wash and replace what comes out? I don't want to jeopardize my wall. Right now it is sound.

I'm open to all suggestions.

Thanks,

RedTartan

[RedTartan]

I didn't see posts 6 & 7 when I posted just now.

Watcher48, that's a fine solution. I wasn't looking for easy, I was looking for right so that I won't have to worry about it again for a very, very long time. What does "tuck point" mean? I that just "tucking" new mortar in between the rock? I'm definitely putting a humidifier down there...

BethW, I will give those people a call. Thanks so much for the link.

RedTartan

[cfabe]

Well, if the mortar is falling apart and has so little cement left in it that it's crumbing when you touch it, your walls are not sound at all. Tuck pointing is where as much of the mortar as possible is removed and replaced with new mortar. With foot thick stone walls that's going to be a challenge. I have done it myself with bricks and it's not hard to get most of the mortar out from one side when you're talking about a 3" brick.

How is the structure of your house? Does it show any foundation problems? Doors that are out of square, un level floors, significant plaster cracking, etc? If the house is still level & square I would do as much as I could to stabilize the existing foundation, this would include replacing the mortar on both the inside and the outside and also probably installing some drainage and waterproofing around the outside of the foundation.

[Watcher48]

Originally Posted by RedTartan

I didn't see posts 6 & 7 when I posted just now.

Watcher48, that's a fine solution. I wasn't looking for easy, I was looking for right so that I won't have to worry about it again for a very, very long time. What does "tuck point" mean? I that just "tucking" new mortar in between the rock? I'm definitely putting a humidifier down there...

BethW, I will give those people a call. Thanks so much for the link.

RedTartan

Cfabe is right about it probably being efflorescence. Pressure washing will remove all the bad and loose mortar. Tuck pointing is exactly what you think, they make a narrow tool for doing that. I would do a small area first to see what happens.
I would also recommend getting hold of any body in a historical society in your area and talk to them. I'm sure you don't have a unique problem.

IN the old days they just back filled the walls with dirt. Now days they put a foot or two wide area of gravel/stone with tile below to get rid of water and moisture.
It can be done inside by cutting a trench around the inside of the wall. putting in stone and tile and running it to a sump to be pumped out. You can then cover it with plastic and pour concrete over to get your floor back More Work

[RedTartan]

Originally Posted by cfabe

Well, if the mortar is falling apart and has so little cement left in it that it's crumbing when you touch it, your walls are not sound at all. Tuck pointing is where as much of the mortar as possible is removed and replaced with new mortar. With foot thick stone walls that's going to be a challenge. I have done it myself with bricks and it's not hard to get most of the mortar out from one side when you're talking about a 3" brick.

How is the structure of your house? Does it show any foundation problems? Doors that are out of square, un level floors, significant plaster cracking, etc? If the house is still level & square I would do as much as I could to stabilize the existing foundation, this would include replacing the mortar on both the inside and the outside and also probably installing some drainage and waterproofing around the outside of the foundation.

No, the house doesn't show any foundation problems, which is amazing since the house 183 years old. We still have original plaster in some rooms that have very minor cracking, doors are fine. My FIL is a general contractor and he looked at the foundation before we bought the house. I'm concerned that digging out the outside of the foundation would be enough to destabilize the walls.

Some of the stones in my foundation are huge (like coffin sized, but longer.) They're not round. They're mostly flat and it doesn't look like there was much mortar at all to begin with in most places which could explain why I don't have a lot of structural damage. The biggest ones are at the top of the basement walls. I think they serve as stone footers. I think I'm going to have to talk to those people in Virginia that BethW posted before I do anything. I'm definitely going to have to get mortar from them or someone like them...

RedTartan

[RedTartan]

Originally Posted by RedTartan

My house is really old. The basement walls are made of large, rounded stones mortared together.
RedTartan

This is where my original post was misleading, but not intentionally so. Before I scraped off some of the paint I thought I had rounded stones. Actually, what I have is really huge rectangular stones with curvy sides that looked like smaller, rounder stones. Now that I can see where the stones stop and start better the above is no longer accurate. Sorry.

RedTartan

ETA: This is what my walls look like except much bigger stones, not so many round ones, and painted. I hope this helps. This wall doesn't have any mortar. Mine does. Just a tiny bit though.

[Farmerwilly2]

Do a search for lime putty mixes. I'd not use any modern mortar in the wall. The old lime mortars allowed flexibility, would swell to block moisture but not enough to caused the stone to spaul. Roofing an bricklaying tool suppliers sell a chisel that will clean out joints. The mason suppliers also sell bags (kind of like a cake decorating bag) that will let you pipe in the lime mortar and then tool it. If I recall you'll not need to remove all of the mortar in the joint. You need to be patient with the lime mortar as it can take up to a month to cure. Once again though, do your research/homework before you jump in. If you have a local mason supply store you might take a sample of the old mortar and see if they can give you any clue to it's composition. In an old building they probably used a very local source for the sand because of the weight to move it by wagon.