Hello,
I own a fieldstone home, circa 1850. The original mortar, as seen crumbling in the basement, appears to be a combination of sand, clay and lime. A great deal of it has fallen out over time into the basement leaving deep gaps between some of the stones, some gaps two to three inches deep. I have three questions.
1) as of 2023, is there a mortar that is better at keeping moisture to a minimum in a partially below grade basement other than lime mortar?
2) if i fill in the voids, and decide to plaster the surface smooth, are there any additional steps I can take to minimize moisture transfer through the basement walls?
3) part of the basement has wainscoting. I have no idea if there is a vapor barrier behind the wood. If I wanted to place wainscoting around the rest of the basement, what should I place between the wood and the stone wall?
thanks for any advice
Replies
look at the National Park recommendations.
would consider 1:1:4 -- portland cement/lime/sand mix for repointing.
https://www.nps.gov/orgs/1739/preservation-briefs.htm
lime parging or lime-wash is a good traditional coating for below grade masonry wall interiors. the lime helps control moisture.
would be very careful about wainscott since you may make conditions favorable to mold. [dark, cool, moist, and food source.]
Thank you very much!
There seems to be a popular (online) anti-Portland sentiment when repointing old homes. What is the risk if it’s an interior versus exterior wall?
straight portland cement is too hard and doesn't have the water resistance and elasticity of a portland/lime mix. mortar is sacrificial and protects the stone by failing first. if the mortar is harder than the stone, then you can get face-spalling during freeze/thaw expansion. ice is about four percent larger by volume than water [from what i remember]