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Community and Q&A

How to prevent mold/moisture after sealing a cove joint behind finished walls in walkout basement?

Jenny | Posted in GBA Pro Help on

Hi Martin,

We have an open 1/2 inch cove joint in our walkout basement.  There was 6 inches to 1 foot of mold above the joint on the cinder walls in the mechanical room (on all the perimeter walls against soil).  The mold was remediated and Kilz was painted over.  We are being told there is likely mold above the joint behind the finished walls that run the perimeter of our basement as well.  Not sure if the mold in the mechanical room is from vapor coming up through the crack, vapor diffusion, condensation, or hydrostatic pressure.  The mold in the mechanical room followed a pretty symmetrical line/height on the wall.

We are being advised to open the walls, treat mold, and seal the joint somehow.  After this is done, how do we insulate and ventilate the walls properly so this doesn’t recur.  If condensation can travel from the outside of the home to the interior part of the year, how do you prevent the growth from recurring?  Is the spray foam or rigid foam supposed to dry condensation out?

We have received advice to seal the joint and install radon mitigation, and one person advised a dimple board, though I am not sure that would seal the cove joint.  We are in a mixed climate in MN.  We have a vapor barrier behind our drywall currently, and we don’t have fresh air coming into the home.   We also need to do some grading d/t moisture intrusion on one wall.  I would like to remediate correctly as I am high for mycotoxins and we don’t want a recurrence of mold.  Will sealing the joint stop the mold from forming above it?  Or, can condensation still occur moving from exterior to interior even if the grading is done well?  What would help if this is the case?  I have been enjoying reading your posts but it’s quite the learning curve for me!


Jenny in Minnesota

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