How to: Block Filler Over Stucco Paint

If you are painting over a stucco wall that has been painted before, you may need to first apply a new coat of block filler. Stucco walls have a high alkalinity because of the lime used to make the stucco. This can cause new paint to peel if the stucco is not first sealed with block filler. You can usually tell if you need to apply block filler by checking for "efflorescence," which is the appearance of white, crusty salt deposits on the wall. Even if the stucco is chalky or looks porous through the old layer of paint, you should apply block filler.

Bristle brush or power washer
Paint brush
Paint roller

Instructions

- 1
  Clean the surface of the stucco wall before you paint it. Use a stiff brush or a power washer. Remove all salt deposits and other debris. Leave a rough surface so the block filler will adhere. Use a wire brush if needed. You do not have to remove the old layer of paint, unless you want to remove it for cosmetic reasons.
- 2
  Fill in any cracks and holes with caulk while the wall is drying.
- 3
  Dampen the stucco surface immediately before applying the block filler. This will extend the drying time of the block filler, causing it to absorb more deeply into the underlying surface.
- 4
  Apply the block filler with a brush or roller. You will only need one thick layer.

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