Old Stone Basement Foundation FAQ by Randy Ruth

This is part of a series of blog entries that will feature mason, Randy Ruth.

Randy was the former lab technician at LimeWorks.us and received lots of questions on masonry and the use of our materials. We post some of these questions on our blog.  Look for “FAQ” in other titles of our blog.

Q: I have an old stone basement foundation (house was built in 1900) and need to “re-point” or fill in holes in the basement walls. Would your Ecologic mortar work? I am not sure that lime based mortar was used originally; would this still be OK or how can I tell if lime was used?

A: “cement” was not produced in the United States until 1870 in Coplay, PA, only up until around 1910 was Portland cement starting to find its place in society as a masonry binder. Prior to 1910, most mortars used were based on either lime putty, Natural hydraulic quicklime, or natural cement. Regardless of what the exact mix design was used to build your basement foundation, Ecologic™ Mortar would most likely be suitable for repointing your old stone basement foundation walls as it would be sympathetic to the adjacent mortar mix by maintaining good vapor permeability. An easy way to determine if you have a lime based mortar, especially in stone construction, is to break a piece from the wall and visually inspect for any white nodules or specks. The white nodules are an indicator of what is called a “hot lime” mix and commonly found in stonework. Any presence of those nodules or specks suggests a high lime content mortar, and should thus be repaired with a comparable material.

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