Is it alright to strip the paint from Ocala block to expose the original bare-block surface?
Wednesday, November 25, 2020
We don’t recommend it for several reasons. First, any bare concrete block, Ocala block included, absorbs water from rain. This type of block is less absorbent than modern concrete block, but the process of chemical stripping or blasting away the multiple coats of paint that have accumulated over the years will deteriorate the surface of the block, making it more porous.
Block is definitely forgiving of a little moisture intrusion. It doesn’t rot and ordinarily any water that is absorbed evaporates away. But when you combine the roughened surface with the inevitable settlement cracks and eroded mortar of an older block home—plus take away the moisture retardant paint coating—the block can easily become saturated beyond the surface in a driving rain.
Small cracks that meander down a wall in stair-step pattern, like in the photo above, are not as innocent as they look. A crack only 1/32” wide (less than the thickness of a dime) and three feet long is equivalent to a one-and-a-quarter inch diameter hole drilled in wall for water intrusion. Paint easily spans and seals these hairline cracks.
And stripping paint off a wall with inset grout joints is neither easy or cheap. If you do decide to try to reclaim the mid-century block surface, we recommend applying and maintaining a clear sealer recommended by your painting contractor to protect the surface against moisture intrusion when you’re done.
Why was bare Ocala block not a problem when it was so popular with Florida architects in the mid-20th century? Homes weren’t air conditioned back then, with windows open for ventilation during the hot and humid months, so there wasn’t the temperature and humidity differential between outside and inside that induces moisture migration, and the surface had not yet been roughed up by years of weather eposure and settlement.
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