No, if you are resealing using the same Black Diamond Coatings product.  However, if sealing over an older sealer or solvent based sealer, stripping may be necessary if sealer remains on the surface.  Remember that the chemical closest to the hardscape will fail first, so old sealer remaining on the surface prior to sealing with any of our sealers will potentially “push” the new sealer off.  If you decide to strip your hardscape surface, strippers designed to remove paint will work.  Follow the manufacturer’s application instructions, and ensure that all stripper is completely removed from the surface prior to sealing.