What can I use to waterproof a masonry chimney crown for a wood burning fireplace. Can I use standard concrete waterproofing liquid that brushes on, or does the crown require something totally different?
I used Quikrete Concrete Sealer No.8800 on my newly poured and cured crown. It went on rather milky looking but dried absolutely clear. It's been only a few years but still looks new! Got it from one of the from the big box stores.
If the crown has cracks & other imperfections, it will need more than just a typical sealer.
If it's in good shape,, well it's probably not the cause of any leakage. If you are just wanting to seal it to extend the lifespan of the crown, I'd suggest looking for a penetratign sealer, like a solvent-based siloxane sealer.