Last night at around 10:00 p.m. I finished relaying a small section of our foundation wall. This wall is in the original part of our house, on which construction began in November 1885 and was completed sometime in early 1886. I this period, the most common foundation for a typical residential building like ours was one of limestone rubble, roughly coursed and held together with a fill of dirt and lime and then pointed with a soft, lime-heavy mortar.
When we purchased the house, a few sections of our foundation had significant erosion problems due to the intrusion of tree roots, water infiltration and -- most common -- application of hydraulic cement that fell off, pulling out mortar. After making sure that the tree and water problems were eradicated, I have systematically ground these areas out and repointed them with mortar that's a little harder than the original type used but soft enough to keep the limestone faces from spalling, a common problem brought on when people point their foundation walls with inappropriate hard mortars or cements.
The area that I finished last night was an area under a window opening where the inner stones had fallen out completely, leaving an area about a foot deep, three feet tall and four feet wide without stone. The cause of this small collapse seems to be due to water infiltration when the basement window opening was left open and crudely boarded (not sealed) for about two years following a fire in the basement in 2003.
First, I cleaned the area of the loose fill mixture and other debris. Then I ground out mortar and fill around the opening to make a good key into the stable sections of the wall. I began laying the stones a few weeks ago, one course at a time because rubble stone needs to set slowly so that the courses don't fail or push out while setting. I worked in evenings and on weekends. Of course, since the rubble stone was packed in while the entire width of the wall was being raised systematically, I had trouble getting the same stones to fit their places in the wall. I also did not know the original placement, although the outside stones carried traces of a green paint that someone once painted our basement walls (creating another problem for the mortar in the process). How did I get the wall section firm without simply cheating by using mortar to fill gaps?
I turned to the resources at our disposal: the foundation walls of the seven buildings that stood on the lots adjacent to our house that we also own. All of these walls are intact under the ground, and some are clearly visible poking up through the dirt. I mined the top levels of these walls to obtain stones to fit where the original stones could not. Sometimes, I used a hammer and chisel to cut stones to fit.
In the end, I spend many hours and about $25 in mortar to rebuild the foundation area. Time will tell if my work will hold up, but it sure beats the bids ranging from $500 to $1,100 that we had to repair that area. And our bidders proposed using block or other ways of making the job easier for them -- but not cheaper for us. I'd rather make a repair using a traditional method and pick up the skills to make it again if need be.