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Community and Q&A

Existing Basement Moisture Control Questions

sb1616ne | Posted in General Questions on


I am a long time lurker on here and a recent GBA Prime member. We have an older home that we are in the middle of a renovation and addition to. 

What we have is two existing basements that we would like to reduce the moisture load as much as possible, here are is what we have: 

East basement is an exiting 1910 basement. The foundation supporting the house is dry stacked field stones from grade to 3 ft below grade. Then they dry stacked a large slab of granite, then 2ft of brick and mortar. Then inside later(I think in the 70’s) they dug the basement out to 7′ deep by stepping in 5 feet then building a block wall with a poured floor. The soil here is the most well draining and sandy/rocky material I have ever seen. Its like a sandy river bed! Also, this foundation has stayed nearly dead level for over 100 years!  This basement we will not be finishing, but we would like to insulate it and reduce the moisture load passing to the rest of the house. Its not moldy down there, but clammy. This basement will just be a mechanical room with our boiler and HW heater plus storage. The spray foam guy wants to spray it all, but I do not want to spray foam for the fact I cannot get to the masonry easily down the road to repoint, etc if ever needed. Maybe I should just have them spray foam it and forget about it as all the masonry is in good shape now. 

West basement is a traditionally poured full height foundation from 1970. No exterior water proofing or dam proofing was ever done to this. Once again the soils are great here and no standing water ever, just a clammy feel in general. We want to partially finish this basement to use it as a gym/play room. My plan is to frame walls and have them spray foamed, but leave the poured floor with just a rubber gym mat type material on it. Part of the plan was to dig around this foundation and install proper footing drains as well as water proofing, however when I got close to footing level I noticed existing perforated cement drainage pipe. Well that turned out to be asbestos cement pipe and I left it buried and abandoned that project, haha. We have dealt with asbestos on some pipe insulation and fire place mortar so I do not want to open up the can of worms again if I do not have to. 

So some general questions: 

1. For the existing masonry(block walls, and poured walls), do products like Drylok work when used just on the interior surface to reduce or eliminate moisture transmission. In the case for both of these walls I cannot seal the exterior surface with anything. 

2. What is the general consensus on closed cell spray foam over concrete? All the spray foam contractors seem to use it on walls without question. But for example my case with no exterior damp or water proofing could there be issues down the road with moisture trying to migrate through the masonry into the home but stopping when it hit the spray foam? 


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