I am trying to guess what type of stone is present in this foundation (see attached photo). I want to be sure before I add mortar into the areas that need tuck pointing.
Thanks for your advice!
The type of stone maybe less critical to know than the type of orginal mortar.
Older lime-based mortar is much softer than the Portland cement based product that's available now. They do NOT combine well.
Find out which you've got, before starting, at use what matches. You may have to buy lime-based mortar online. Though in some very restoration-minded areas you can get it a real masonry suppliers (not Big Box).
I can't tell which stone you have, it is likely to be local, and locals will be able to ID it accurately. It looks sandstoney to me, but what do I know? Foundations here (upstate NY) are field stone (schist, bluestone, with some quartzy round rubble rocks as they turned up). A few miles north of me waste slate blocks are popular. In my 19th c farmhouse foundation I have a decorative course of VT marble at the cornerstones. I live only a few milies from the VT quarry area.
Unless a building is very high-end, foundations are almost always made from from pretty local stone. Unless you live in a naturally stone-free area.
Any tricks to know if its Lime or Portland Cement? Im assuming the original mortar was lime since it was built in 1916....? Maybe someone used Portland cement later on. What are the dangers of using Lime if there was some portland cement mortar in there from previous fixes?
Thanks for the help
Im assuming the original mortar was lime since it was built in 1916....?
More likely to be a mixture of lime and Portland than strictly one or the other.
The general rule in the US is that any building built from the mid 1880s to 1930 uses a mixture of mixture of lime putty, Portland cement, sand and colourings.
According to The Canadian Encyclopedia, Portland cement was imported to Canada from England until the first domestic plant was established in 1889 in Hull, followed shortly later by plants in Napanee, Shallow Lake (on the Bruce Peninsula) Ontario and Montreal; and in Vancouver in 1893.
Matching the original mortar in every way requires expertise probably best left to specialists and experienced masons.
Here is a link that might be useful: Repointing Masonry in Historic Masonry Buildings
This post was edited by worthy on Sun, Apr 14, 13 at 23:20