How to Install Quarter Round Tile Around an Undermount Sink

Place a layer of thinset mortar onto the rear of a corner piece of the quarter round tile. Press the corner piece onto the corner of the sink opening, with the flat of the piece flush with the countertop surface and the small ledge piece overlapping the edge and concealing the cement board in the corner over the sink.

Place a tile spacer next to the corner tile. Butter the rear of one of the corner round tiles with the margin trowel. Press the tile onto the edge of the sink opening nest to the corner piece with the spacer providing a slight gap for grouting.

Continue placing quarter rounds along the edge of the opening with spacers between them until you run out of space for full-sized tile pieces. Place a spacer against the edge of the last full-sized piece. Position the corner piece in the next corner, and then the spacer against the corner’s edge. Measure the gap between the two spacers, and then use a tile saw to cut quarter round tile to fit the space. Butter the rear and set the tile in place, completing the first sink opening edge.

Repeat the placement process for the rest of the tiles along the edge of the sink.

Wipe the face of the tiles with a damp sponge to remove any mortar that may have fallen onto them or squeezed out between the tiles.

Set tile over the rest of the countertop surface, using spacers to separate the full-sized tiles on the surface of the counter from the quarter round tiles around the sink opening.