Check for Dampness?

If unsure about moisture within the pool substrate, particularly with Marblesheen (Pebblecrete) and render, a simple test will tell you if it’s too damp to paint.

Get some heavy-duty clear plastic sheet and cut into squares about 600 mm. (you need 2 – 4 of them) Tape them securely around all edges to the pool surface and leave 16 hours, (overnight).

Check to see if any moisture droplets on underside next day. If so, it’s too wet to paint.

Remove, let pool dry out for another few sunny, windy days and repeat until no moisture is present.

Then you can paint. If you paint over a surface with moisture behind (underneath) you risk the new paint bubbling up and coming off, as shown in the pictures here, under the clear plastic. (This is not the same as some dampness on the surface, which is acceptable) The right-hand picture shows moisture droplets on the underside of a plastic sheet after overnight placement

A clear plastic sheet on bottom.

Moisture droplets on underside of sheet. Meaning too wet to paint. The new paint has come away as it was too wet within the substrate to paint. (The white underlying surface is visible)