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Thread: Pool replaster question? "Chipping" out plaster vs. "Sandblasting" out old plaster

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    Pool replaster question? "Chipping" out plaster vs. "Sandblasting" out old plaster

    Last week I got a couple of estimates to replaster my pool. One contractor stated, "You pool is 17 years old and has never been replastered. To maintain the integrity of your original pool shell, we would sandblast the old plaster, then apply a bonding agent, then apply a new plaster coat to the bonding agent." He simply refused to chip it out by saying a chip out is for a pool that has been sandblasted a couple of times first and is 20 years or older. The next day another contractor stated: "The only way to get proper bonding on a new plaster coat is to chip it out down to the gunite shell. Whatever you do, DO NOT SANDBLAST THE ORIGINAL OLD PLASTER AND APPLY A NEW PLASTER COAT TO ANY BONDING COAT. IT WILL NOT ADHERE PROPERLY AND YOU WILL BE WASTING YOUR MONEY." Which one of these contractors is telling me the truth?

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    JasonLion's Avatar
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    May 2007
    Silver Spring, MD

    Re: Pool replaster question? "Chipping" out plaster vs. "Sandblasting" out old plast

    They are both partially right and partially wrong, though the second one is being more misleading.

    If the old plaster is sound and well adhered to the pool, sandblasting and bond coat with a chip out just around the fixtures is generally just fine. However, with older plaster you almost always see some delamination, where the old plaster is not adhering to the shell of the pool. The new layer may stick to the old plaster just fine, but the old plaster can then come off of the pool shell, ruining both layers. The second layer of plaster puts additional stress on the old plaster, so it can fail even if it seems fine to a casual inspection right now.

    Common practice these days is to sandblast and add a new layer one, two, or three times, and then to chip out and replace everything the next time. However, it is important to do a through evaluation of the old pool to see what kind of shape the old plaster is in before making a final decision. Small spots that are delaminating can be chipped out locally, but any kind of extensive delamination means taking out all of the old plaster.

    So the first builder sounds a little over confident, while the second builder is sounding a little pessimistic (probably because they have had problems in the past).
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    Re: Pool replaster question? "Chipping" out plaster vs. "Sandblasting" out old plast

    Thank you. I think I prefer to go with the second contractor and the chip out method as I am concerned about what you stated about the new plaster applied over old plaster and potentially failing. I got another estimate from a third contractor and he recommended a chip out and said the same thing you stated.

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