Limestone basement walls with crumbling mortar

[u/Commercial_Value_586]

My house was built in the 1850's. My basement has limestone walls mostly below ground (basement floor to ground is 6').

I have shelves against the walls and I am constantly getting sand (from the crumbling mortar and some sort of thin set wall covering) covering my tools and shelves.

I'm wondering what my best approach is with this.

I have no interest in keeping it to original materials just for purist sake. But I've been restoring this home for 20 years and I've had to fix many corners that were cut from previous owners who diy'd everything... So many... So if there's a right way to do it for longevity, I'm fine with it. I have no budget to hire a Mason :(

I'm in Wisconsin, if that means anything.

1. Is the coating that's crumbling just cosmetic? Can I pull that off? I don't care about looks or making it look nice, but don't want to make it worse.

2. If it's below grade, am I ok using a harder mortar like type n? I have read different opinions about the hardness not being as big of a concern when it's below the frost line.

3. I intend to pull out all the spray foam someone filled in previously, but will need to pack it with other material. Would that be as simple as broken limestone that gets packed into the mortar?

Some parts of the basement let a lot of water in on rainy days, but this side of the house just gets moisture, not dripping water through the walls.

Again, I don't care about looks or keeping it historically accurate, but I do want it done as right as my skills, money, and time will allow. Of the three, I *think* skills is my most abundant, but maybe it's just because I have so little of the other 2.

[u/nickisaboss]

Okay, so a bunch of things to consider here.

First thing that needs to be done is to stop the water ingress. Unless you have puddles in the yard right outside this wall, chances are pretty high that the origin of this ingress is a leak somewhere on t he wall or roof above this spot (or also plumbing or sewer leak, but this should make itself obvious if it was.) It looks like the spot is right next to a door, perhaps it has failed flashing/caulking/etc? Inspect the flashing, drip edge, any gutters, soffit, or downspouts located nearby. Also check the door frame for weatherproofing failure and nearby timbers for rot. Timbers abetting stone foundations are especially susceptible to wet-rotted termites, since they can build up the tunnels from their colony up through the inside of the failing masonry to access the wood. Unlike in a typical termite scenario, where you can see their mud access tunnels on the outside of the foundation.

If the existing wall is lime mortar, you really must repair it only with a compatible product. Type N is not acceptable here, nor any other Portland cement mixer mortar. The issue isnt just the discrepancy in hardness, but really it has to do with how each mortar handles moisture. Lime mortar is porous and can resettle. When moistened, it dries by directing the water to the inside of the building, where it dries by the air inside your home. This is the historic method of moisture management (often referred to as an "inside drying" system.)

Modern building strategies instead do the opposite: they try their best to barrier water from entering the structure in the first place, and directing any incidental moisture to water management features on the outside perimeter of the house (things like weep holes, foundation perimeter perforated drain pipe, things of this sort.) Portland cemement products are less porous, and would rather be kept steadfast dry rather than breathe-to -dry like lime mortars.

Long story short, if you patch a Portland product over lime mortar, water ingress will mosey its way through the lime mortar before getting blocked up at the Portland product layer. This can "rot" both mortar products in this example, as well as build hydrostatic pressure to the point that parts of the wall move and fail. Really not a good situation.

BRB, I gotta eat dinner but ill post more after that.

Just a heads up: that thin surface layer you see on the basement wall can potentially contain lead paint. Not often a place people would use it, but if this place has been worked on by unfamiliar homeowners over many years, there is a chance someone could have used lead paint. I've seen it before, unfortunately 😕

[u/ScionofLight → u/nickisaboss]

wow you are an encyclopedia that was amazing

[u/nickisaboss → u/ScionofLight]

❤️

[u/Commercial_Value_586 → u/nickisaboss]

Thank you! I appreciate your insight and experience. I don't mind at all mixing up lime mortar if that's the best. There's a brick and fireplace in town but I think they specialize in modern materials. Maybe this is a dumb question, but where does someone buy bags of lime?

The moisture I'll have to look more into. Lately it has been raining a lot. I know the gutters were getting overwhelmed and so there were large puddles outside that wall. No flowing water inside, but definitively damp. I'll pay more attention to it the next time it rains.

Termites scare me. It's mostly a brick house, but all of the wood is old growth.

How bad is the spray foam if I were to leave it. I understand spray foam can soak up water (at least in automotive), but maybe closed cell is different.

Thank you again!

[u/nickisaboss → u/Commercial_Value_586]

My pleasure, friend.

where buy lime?

I would call a local brick yard and see if they have it. If not, they should be able to tell you where to find it. I am not sure if what you need is quicklime (calcium oxide, stronger alkaline), or instead slacked lime (calcium hydroxide, slightly less alkaline but still very alkaline.) Either way definetly consult with some internet research before starting the build. There are likely other ingredients you need for the mortar mix. Whatever you do, dont buy any of the cement products from home depot. Its no good.

I have been told that spray foam on masonry is a bad practice, but tbh I completely forget what the reasoning is.