Which type of caulk to use to seal cracks?


Old 10-11-17, 06:06 PM
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Which type of caulk to use to seal cracks?

Concrete block stucco building has some cracks on the exterior wall. Hairline cracks with the widest gap about 1/32" wide.

I took out an angle grinder and widened the gap into a "V" shape. I understand best practice is to apply caulk or sealant to the crack at the narrowest point of the "V" then patch with stucco.

What type of caulk is best for this application? Silicone? Latex?
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Old 10-11-17, 07:29 PM
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Definitely not silicone. I would say to use a concrete expansion joint sealant, such as NP1, or Loctite S10 or Sikaflex 2c. Apply it as neatly as possible using as little caulk as possible (cut the smallest tip possible on the nozzle), then tool it down into the notch with your finger, dipping your finger in paint thinner as needed to smooth it. Keep a rag handy to keep the nozzle clean.

You should not end up with a big fat 1/2" wide mess. The caulk should stay within the notch... you control that by how much caulk you put on.

If the cracks correspond to the mortar joints in the cmu, it will probably crack again.

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