A styrene butadiene copolymer latex, which increases flexibility of cement screeds and mortars and improves water and chemical resistance and durability. Suitable for internal and external floors and rendering in areas of continual or intermittent water and chemical contact. Excellent waterproofing admixture that improves adhesion of cementitious screeds and reduces shrinkage and cracking when repairing floor screeds. Also ideal as a bonding agent for new to old concrete.