I am currently working on my basement and am in the middle of re-pointing my the 120 year old granite foundation. Much of the mortar has turned into something that looks like plaster dust, so I am removing and replacing it. After removing some of the old mortar, there are some large gaps inside between the blocks, like that I can put my arm into. I guess they didn't do much dressing of the blocks on site but just stacked them up and mortared them into place. I have used some great stuff to fill some of the gaps, but I think I need a much larger volume product if I'm going to fill all of them.
There has never been any issue with water in the basement, and some of the gaps are obviously continuous to the outside, so the drainage must be good enough to prevent leaks. Even so, I think it is a good idea to fill these gaps since I have it all open. It will also be allot easier to re-point if the bigger gaps have been reduced considerably.
I have added some pictures below.
The first picture is a section of the wall I am working on. All the the loose mortar has been removed.
The second picture is of a common gap I am seeing. This vertical gap runs for about 2 feet and is about 1-3 inches wide and about 1 foot deep.
The third picture is of a horizontal gap that is 1 foot deep 18 inches wide and about 5 inches tall. There are two loose pieces of granite sitting at the front of the gap. In the last picture, I have removed the loose pieces and you can see all the way into the gap.
There are two places where there is an ~8x8 inch gap that runs all the way through. I can see the underground dirt on the other side. I have no idea why there isn't water coming in here, but there is a cantilevered section of the house over that area and the grade slopes away from the house pretty well. I guess the overhand is keeping it dry enough to keep the water out. There are some signs of moisture in this area though, but nothing like standing water.
I found this video
by a group near here called the mended wall. They do allot of conservation/restoration of homes much older than mine. The video shows Andrew doing most of the same things I have been doing, removing loose mortar and stone, using a vacuum to remove dirt and debris, etc. He just filled all the gaps with a mixture of sand mix and type N lime. He didn't specify the proportions, so I'm not sure where to go with that. These are also restorations that aim to preserve the historical significance of the home and I don't know if that affects the techniques I would want or not.
advised what I was thinking about, which is to inject closed cell expanding foam into the gaps, which would be much quicker. The article didn't specify the type of foam to use or where to get it.
I have also thought of just shoveling concrete into the large areas to fill as much as possible and then using standard mortar mix to finish the pointing, or using cement to fill as much as possible, adding an inch or two of spray foam to seal and insulate, and then pointing. One of the problems is that some of the gaps have narrow openings, but get fairly large as they go back. It would be pretty difficult go get any kind of mortar back in there without some kind of pump. I also know there are other expanding hydraulic cement like products that are used for filling and sealing applications.
I don't really know if this wall need structural reinforcement or not. It has been where it is for more than 120 years with no shifting, so I suspect that it does not need much more than would be provided by replacing the loose rock and re-pointing enough to fill the gaps. Adding additional structure isn't going to do any harm however, and it would be nice if this remained stable for another 120 years.
There are allot of possibilities and I am a bit in the weeds here, so I would really appreciate any suggestions.
This site seems to have a reasonable selection of expanding foam,
If I do use foam, I'm not really sure what to get, 1-component, 2-component, fire block, etc. I'm not sure which of these would qualify as "structural". The products at this site range in price from $90-$800 and I don't want to spend allot here unless it is really necessary. It is hard to tell how large the largest gaps are, but I can always make repeat applications if necessary. Most of these things are advertised as waterproof, but I don't really know what that means in practice.
I'm not really sure what to get, or where to get it, so suggestions would be appreciated. Is there a standard for this sort of application?