Vapor Barrier for Concrete-Block Basement
- Goal: finish my basement to a degree that it is rentable and comfortable year round.
- I have a house built in the 1950s.
- According to the previous owner, the basement had water issues in the past.
- To correct them, he hired a company that installed an interior drainage system.
- This consists of a small gap at the seam where the concrete block wall meets the concrete floor. The walls were also treated with some kind of waterproof paint. This was over 10 years ago. There is a lifetime warranty on this work.
- I would like to finish the basement to be a separate living space, which is allowed under local codes.
- The basement is a walk-out, with 20% fully below grade and 60% partially below grade.
- On every wall, even the ones that are not very far below grade, there are small patches of paint that bulges out. When scraped, these are filled with flaky powder, and have bare concrete block behind them.
- Taping plastic to the walls and floor results in condensation underneath the plastic. Rubber mats left on the floor have condensation underneath them. According to my (rather old) dehumidifier, humidity is about 60%.
- Because there is a lifetime warranty, I think it makes sense to have the same waterproofing company address the bulging paint and interior moisture.
- They propose covering the walls in a membrane for about $3,000.
- As I will also be covering the walls in extruded foam panels for insulation, is it redundant? I’m thinking the membrane can go down into the seam to ensure that all water drips into it, but I am a bit concerned about what I don’t know, for example the risk of mold. I am in the south where the temperature fluctuates wildly and humidity is naturally high.
To be clear, I am absolutely fine doubling up if that is the correct choice, but want to be sure I am not missing anything. For example, this article seemed to be against the idea of installing poly against the concrete block: https://www.ecohome.net/guides/2271/why-are-basements-moldy/
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