|I've been using and recommending DAP Dynaflex caulk for many years -- since it was called Formula 230. I like it because it remains flexible for a long time, preventing cracking along the sealed seam. But, I must now face the fact that is seems to be an aggressive growth medium for mildew.|
In the following pictures the dark/black caulked areas are mildew -- not grime.
|In each case when I rework the seam, I scrub it with a toothbrush and TSP solution. I follow this with a bleach solution. I then prime the area with Zinser Bulls Eye 123 primer, and top it with two coats of Pratt-Lambert Accolade. All in an attempt to prevent the mildew coming back. But, to no avail.|
The seam in this next picture has been redone three times (making a total of 4 times including the original).
The following seams have been redone twice
This seam is a caulked vertical joint between two 4x8 pieces of exterior wall paneling
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