I have a shed base on piers topped with plywood that was finished last Winter and covered up to help protect from the elements.

However some water made it through (or general dampness of being covered) through the tarp material and has made the plywood grow a little black mould. The timber joists are fine though, I guess ply is a bit more porous.

I'm going to coat the joists and ply with crecote preservative to help prevent this happening again. Do I need to remove the mould before and if so how. Anything else I can do to prevent further mould - it won't be covered again so I think it was just due to lack of airflow.

Thanks in advanceenter image description here


Yes, you should remove the mold. It seeps into the wood and would prevent your sealers from doing their job to the fullest. Bleach is good for surface mold but it doesn't penetrate the surface. I've used white vinegar, one cup to 3 quarts water. Scrub the mixture on the wood and then spray off with water. Let the wood totally dry and follow the directions for your preservative. Good luck and stay safe out there.

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