Fognings

Fognings, in the context of tiling and masonry, refers to the process of filling joints between tiles or stones with grout. The purpose is to secure the tiles, distribute loads at the joints, and prevent water, dirt, and debris from penetrating behind the tile surface. Grout also defines the visual pattern of the tiled surface.

Materials used for fognings include cementitious grout (sanded and unsanded), epoxy grout, and, less commonly, urethane grout. Sanded grout is typically used for joints wider than about 3 mm to resist cracking, while unsanded grout is used for fine joints under 3 mm. Epoxy grout offers high resistance to staining and water intrusion but is harder to work with and more expensive. Grout colors are chosen to complement or contrast with the tile.

Application involves several steps. First, joints should be clean and dry. The grout is mixed according to the manufacturer’s ratio and then pressed into the joints with a rubber grout float at a 45-degree angle to ensure full filling. After the grout has set enough to bead on the surface, excess grout is wiped away with a damp sponge, leaving the joints clean and smooth. Final curing should follow the product’s guidance, avoiding excessive moisture or rapid drying. Perimeter gaps or joints adjacent to movement zones often require separate expansion joints, which are filled with silicone or a similar flexible sealant rather than traditional grout.

Maintenance includes cleaning with pH-neutral cleaners to avoid weakening the grout. Cementitious grouts may benefit from a penetrating sealer to reduce staining, while epoxy grouts generally do not require sealing. Cracks or deterioration should be addressed promptly, as ongoing movement can worsen joint damage and tile instability.