Hi all,
I recently bought a 100 year old farm house with a stone foundation. It seems that the mortar is very brittle and is falling out in some areas. There is even a spot where I can actually move the stones due to the lack of mortar (which is a pile of dust on the dirt floor). I realize this is not a old house magazine but I was hoping someone out there could tell me the best/most economical repair for this situation. I’ve heard I cant use regular mortar to fill the voids, because it won’t allow for natural movement. What should I do?????? (p.s. I live in Rochester NY if climate is an issue to consider in this matter)
thanks
Replies
I live just down the road (central NY) and also have about a 100-year old house with a stone foundation. I've repaired the foundation in several areas where the mortar was gone or on its way to being gone. Basically, you need to scrape out all the loose mortar out of the joints (reach in as far as you can into the joints). I usually used a screwdriver and a wire brush followed by a shop vac. Repack the joints with mortar and tool (shape) the joints to match the other existing joints in the foundation. I think I used Quickrete's Type S, to which I only needed to add water.
If you have stones that are loose and they are confined to a small area (maybe up to 2 or 3 feet or so along the foundation length), pull them out (and try to remember how they were put together) and clean out the old mortar as I described above. Mix up new mortar and build back the foundation with the stones you removed, trying to put them back in the same basic configuration they were in before you removed them.
This whole process really isn't that difficult but it may take a while. You're doing the right thing by addressing it now before it gets worse. If you have a long stretch of the foundation wall with loose stones, you may want to involve a pro because of the potential structural problems. The perimeter beam that sits on top of the foundation should be able to temporarily span a few feet while you build back the supporting masonry but you don't want to open up a lot of the wall at one time for fear of overloading the beam.
I know that there are different types of mortar and won't profess to tell you that I know them all and what works/what doesn't. Probably some other more knowledgeable pros with masonry backgrounds can elaborate further. Good luck.
Edit: Not sure what type of movement you can accomodate with mortared stone. I don't think movement considerations is what drives the choice of mortar. More than likely, mortar is chosen based on the type of materials (stone types, etc.). Masonry is notoriously unforgiving of movement so I think your concern over movement with regards to selecting a mortar is moot.
Edited 9/23/2003 5:53:01 PM ET by stonebm
Thanks for your ideas guys. I think I will start by trying to "point up" the stones in the bad section first. (it's onlt about a 2 or 3 sq. ft area) I'm not concerned about a failure as such but I'd like to be proactive and preserve what I can. Here's to old houses and headaches!!!!
The old mortars were lime based instread of portland based.
The down side of that is that in ground contact conditions with water moving through the soil, the liume leaches away, leaving nothing but the sand and the larger stones.
The good point of those lime based mortarts is that they are self healing. In a chimney ort above ground brick wall, a minor crack from settlement or shrinkage will nbe filed again as lime leaches under rain from the original mortar to the hairline crack.
This means nothing for a hundered year old stone foundation that is ready to fail. Your choices are to replace the foundation a section at a time with new concrete or block, or to save what you have by repacking the mortar as the previous poster detailed.
The only problem with that is that it only solves the problem from the inside. Water can still penetrate the wall from outside. if it is sitting within the wall stones and freezes, things will move around. It could be necessary to excavate around the foundatuion, repair the exterior, place a new perimeter drain, and backfill. I would start with the interior patch and watch how things go. If you have to dig out the exterior, it may be best to just replace the foundation by pieces.
Another fix I have seen is to have a urethene foam insulation spray outfit hit the entier interior of this wall to sealagainst water intrusion, prevent stines fom moving about, and add insulation all in one whack. Not the most professional solution, but it seems to work at least fifty percent of the time to extend the life of what you have for another ten ot twenty years.
Excellence is its own reward!