How to Fasten Countertops

Steel Angles

• Steel angles, which are heavy, L-shaped steel bars with pre-drilled holes, keep countertops secure without glue. Used with laminate and wood countertops, they also secure plywood countertop forms used for tile jobs. With the countertop set in place and shimmed if necessary for leveling, one leg of the angle fits flush against the underside of the countertop, with the other leg flush against the upper interior of the cabinet. Add angles under the counter along the upper back, sides and front of the cabinet. Screws inserted through the holes in the steel fasten the assembly together. Steel angles add support to a wide array of building projects, and some are quite large. For a countertop, choose small, 1 1/2-inch angles and 5/8-inch galvanized screws.

Silicone Caulk

• Silicone caulk seals out water in areas such as kitchens and bathrooms, but it’s also a long-lasting, flexible, waterproof adhesive that sticks to almost anything. The narrow upper edge of cabinets may have few spots thick enough for screws without adding reinforcement. Some materials, such as solid stone, stone composites, resin and concrete, don’t readily accept screws. That is why silicone caulk remains one of the most common ways to fasten countertops to cabinets. Choose 100 percent silicone, as latex/silicone blends don’t have the same bonding ability. A heavy bead or line around the upper edge of the cabinets is all that’s necessary. The countertop rests on the silicone, and its weight adds the right amount of pressure to seat the material into the adhesive.

Construction Adhesive

• Construction adhesive, an oil-based urethane product used in many interior and exterior building projects, cures hard and inflexible. Flexibility is important in some applications, particularly those where both the cabinet and underside of the countertop are wood, but concrete, solid granite and other stone countertops perform better when the chance of movement is reduced. Construction adhesive requires a bit of precision. Alignment adjustments should happen as soon as the countertop is set, which sometimes means keeping an eye on the assembly for a few hours. If the countertop slides out of place as the urethane cures, trying to nudge it back may have no effect.

Screws

• Countertops fastened with screws allow for some movement when humidity levels change, and galvanized screws resist the damp conditions in bathrooms and kitchens. Most traditional cabinets have triangular braces tucked into the upper edge of each corner. Driving screws up through the braces and into the underside of the countertop is enough to hold light-duty counters such as vanity tops. For a more durable assembly, apply silicone around the top edge of the cabinet before setting the countertop in place, then add screws through the braces at each corner. Where countertops rest on a solid surface, such as atop a dresser repurposed as a bathroom vanity, no open spaces in the substrate mean screw placement is less challenging.