Do I Need a Special Counter Top for an Undermount Sink?

Undermount Installation Basics

• Specially designed clips, mounting tracks or support brackets typically anchor an undermount sink to the underside of a counter top. For solid-surface counter tops, such as composite materials, and wood-backed counter tops, such as tile counter tops, builders fasten the mounting hardware directly to the counter's underside. For stone materials, such as granite, builders often set the sink on the stone's plywood substrate and drop the stone slab directly on top of the sink. In this case, the weight of the slab holds the sink in position, rather than fastener-mounted hardware.

Stone and Solid-Surface Countertops

• Although milling sink cut-outs in stone and solid-surface materials is difficult, these materials are ideal candidates for undermount sinks. Solid-surface composites, natural stone and synthetic stone are immune to water damage. Thus, these materials materials won't suffer structural or aesthetic damage from water contact at their exposed interior edge or the joint between the sink and the counter's underside.

Tile Countertop Requirements

• While tile counter tops are suitable for undermount sink installation, creating an attractive, waterproof joint between the sink and edge tiles requires significant planning and labor. Counter top tiles sit on top of materials prone to water damage, such as cement board or plywood substrates. Therefore, it's critical to create tight grout and caulk lines between the tile and sink rim. Additionally, rounding the corner from the counter's top to the rim of the sink requires precise placement of small, specially designed tiles. Properly installed, tile edging creates a visually attractive, long-lasting border around an undermount sink.

Wood and Laminate Countertops

• Sink manufacturers usually discourage the installation of undermount sinks to wooden butcher-block or laminate counters. Both materials easily suffer surface damage and moisture damage along their interior edges. Additionally, sealing the interior edge of a laminate counter's sink cut-out requires adhering a thin strip of laminate around tight curves. Although it's possible to install undermount sinks on these materials, they are the most likely to fail.