Seams in precast concrete countertops are often filled with a color coordinating or color matched filler, often a caulk (siliconized latex acrylic tile caulk or 100% silicone caulk), or perhaps a pigmented epoxy.

Seams in precast countertops are control joints, allowing adjacent slabs to move or deflect due to structural movement of the house and cabinets (often driven by seasonal humidity changes or simply due to settlement of a new structure). Resilient seams allow movement without stressing the concrete.

Rigid epoxy seams, while looking very nice and allowing a near seamless look, are actually too strong and too rigid in some cases. Because the ends of abutting slabs are simply glued together with epoxy, any flexure or deflection is transferred across the joint, causing tension and compression in the concrete. But because the countertop reinforcement is not continuous across the joint, any tension forces are resisted by the concrete alone. The common result is crack will form immediately adjacent to and parallel with an epoxy joint.

Although epoxy filled seams can sometimes look better, epoxy filled seams do not provide the stress isolation that resilient caulk filled seams do. Therefore we recommend using resilient caulk to fill seams in precast concrete countertops.