LSA's Mastic Masters - by Lyn Spessard - License 688825 Concrete Expansion joints,Dow Corning Silicone,sealants, slab gasket, Joint Sealants, pool coping joint sealant, Patios, Sidewalks, Seams, Cracks, Concrete Crack Repair, Power Washing, Pressure Washing, Masonry Sealers, Waterproofing, Houston, Texas, Stamped Concrete, Stained Concrete, Concrete Leveling, Mud Jacking, Concrete Paving, Concrete Contractor, Overlay, Soft Wash We have been pouring mastic for over 30 years throughout Contra Costa, Alameda, Napa, Sonoma, San Jose, Marin, Solano, San Mateo and San Francisco Counties.