What should I do with these basement walls?

[rimtrim]

I recently bought a house built around 1930 or a little before. The foundation is "field stone" (specifically, the home inspector told me it's Wissahickon Schist). It looks like the inside walls were originally "parged" with some kind of soft, brownish mortar that now crumbles easily. About 2/3 of the walls have been recoated sometime later, with a hard Portland cement mix. Some areas of that are now cracking and falling off, basically like the candy shell of an M&M, revealing the softer stuff underneath.

I've read that using Portland cement for parging a stone foundation is a no-no because it traps water in the foundation. However, given that most of it is already done that way, and that job is probably a few decades old, should I just patch it up, or should I chisel off all the way down to the stone faces and start over with a softer mortar mix? That is doable, it would just take time and generate a lot of waste masonry that I would have to pay to get rid of.

Before I do any of that, I'm planning to re-point from the outside on the exposed part of the foundation, because I do have a few water leaks coming through the walls in heavy rains. So, this is just early research so I can start to figure out a series of steps to take to get this basement done over the next few months. The basement is going to remain unfinished, so I don't need it to look beautiful or to be absolutely 100% watertight, but I just want to smooth out the walls and stop the water as much as possible, without doing something that will cause the foundation stones to deteriorate over the years.

-Andrew L

[Jettavr666]

I have no idea if this is the right thing to do or not, but if I was in that situation here is what I would do.

I would cover the inside of all the walls with a chicken wire mesh, and then cement over the walls with a couple thin coats of cement. That way I could level the surface, and seal it as much as possible.

A friend of mine has a house in philly that has huge rodent issues because the foundation is so bad that there are literally large holes that are bored through it. Because he is renting the huse he just took about 7 cans of spray foam insulation and foamed all the holes

He later said he could hear the mice trying to eat away at the foam as they died.

[emmettlodge]

I have no idea if this is the right thing to do or not,

It's not. Sorry

OP -

This problem has plagued just about every owner of a pre-1940 home with deteriorated basement walls since the beginning of time. My parent's home was just as you described, too.

The issue you really have is moisture intrusion through the "block" wall. The bedrock your foundation is made of (Wissahickon) has low porosity (unlike, for example, sandstone) but contains many tiny fractures which are very permeable.

Thin-coat inner wall coatings, such as cementicious skim coats, will always have trouble adhering long-term to your walls because of this constant moisture intrusion behind them. The permeability factor in many mortar thin coats is low, meaning that the moisture moves through your foundation wall and is then stopped on the other side, trapped between the wall and your interior coating. This causes rapidly accelerated breakdown of the wall coating.

You indicate that you have water leaks in the walls during heavy rains. It is likely, given the age of the home and this symptom, that there is no french drain surrounding your foundation. Ideally, your foundation would have a gravel french drain extending down the depth of your wall, with drainage tile in the gravel at the bottom carrying the water that builds up away. Additionally, your wall would benefit from modern basement wall waterproofing, such as tar-fiber wrap.

Unless you solve the water problem from the outside, there is no point putting anything on the inside of the walls.

[rimtrim]

Unless you solve the water problem from the outside, there is no point putting anything on the inside of the walls.

The water problem doesn't seem to be severe -- if it was, I wouldn't have bought the house. I've owned the place since November and we've had a few major rainstorms in that time, so it's been tested pretty well. Basically there are just a few little cracks in the basement walls where water comes trickling in during the heaviest rains. This house is built with a section of the basement extending out under the front porch. That section is where most of the water problem is. Fortunately there's also a floor drain right there, so the water just goes right down the drain rather than flooding.

The steps I was planning to take on the outside were to dig down slightly (maybe 6") and repoint the foundation. The exterior of the foundation is not parged/stucco, it's just exposed stone faces with mortar between. There are some areas where mortar is missing, and I was thinking that might be the source of the water. Once the pointing is done, I would add more soil to build up the grade around the house and prevent water from pooling next to the foundation.

I doubt that excavating and adding an external water barrier is an option...first of all, I've heard that you shouldn't do serious excavating around old foundations because the compacted dirt may be holding the foundation in place. Second, this house is a twin on a small lot...there's about 2 feet of grass between the foundation side wall and the edge of the driveway. There's just not much room to construct a serious drainage system. And of course, something like that would run into big money, which I'd like to avoid.

Really, the condition of the basement walls is not that bad. My main concern was if there's hidden damage happening to the foundation itself as a result of having that cement barrier on the inside. If the cement isn't doing any real harm, I think I can patch it up and get a lot more years out of it, especially if I can make some progress on solving the water problem from the outside.

Thanks,

-Andrew L

[GeoffD]

The cheap first step when you have water intrusion problems is to make sure all the surface water is directed away from the house. Make sure the gutters all work. Make sure the downspouts get the water well away from the house. Make sure you have the grade pitched away from the house. You say you have 2 feet of grass between the foundation and driveway. Is the grass lower than the driveway? If so, fix that.

I wrote a huge check for a perimeter drain system last year. Any time yellow construction equipment is needed, things get expensive.

If you have water intrusion problems, there is little you can do from the inside. You have to stop the water from getting to your foundation in the first place.