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Wet vs damp block – GreenBuildingAdvisor
I’ve seen it said on this site by Martin Holladay and others that a block wall can stay wet for a century or something to that effect, but he also says (and general consensus agrees) that you have to solve any water entry problem before insulating. So, where is the line between a wet block and a water entry problem?
I’ve been monitoring a few spots on my block walls for a while, anticipating insulating them when I finally have the chance, and that time has finally come! Using the square of plastic wrap trick, I didn’t find any moisture behind those spots for years, until last week. I do have a spot of what I’m afraid is mold forming at the bottom of the wall, but I have never seen any water, just darker spots on the wall.
I’ve drilled some inspection holes into the core of the block. Two of the three (including the one where I tested with plastic wrap) show no signs of dampness, even when a paper towel is left there to wick anything that enters. One, at the very bottom, has wicked some water out of it, but never anywhere close to enough that it would do anything more than dampen the surface of a french drain I could install.
So basically, my question is how dry do I need to get it before insulating, what options do I have when there is so little water, and how can I assess when it’s ready?
My plan for insulation is Dupont Thermax white finish to install directly on the block wall in this area, and on existing studs, which are about one inch off the wall in another area that used to be finished years ago with fiberglass batts and drywall.
Thermax white finish is rated to be left exposed, does anyone have a comment if that is real, or marketing BS? I want to be able to use a product that I don’t have to finish over so I can take it down from time to time to ensure I don’t have mold growing behind it, and in some areas, I have foundation anchors I need to adjust yearly.
I had the band joists sprayed a few years ago, the top of the wall seems sealed pretty well.
The last 3 or so courses of the block wall are above ground and my home is in Western Pennsylvania.
Thank you,
Steve
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