Bathroom Remodel: Calculators in Order

A bathroom is small, so quantities are small and mistakes are expensive: a short box of tile from a discontinued lot, a shower that leaks behind the wall, a fan that is too weak to clear the steam. Plan the numbers before demolition.

The order of work is demolition, rough plumbing and wiring, waterproofing, tile, then fixtures and paint. Tile is the biggest line, so measure each surface separately: floor, shower walls, the niche and any tub surround. Add 10 percent waste for straight layouts and 15 percent for diagonal or herringbone, and buy the whole quantity at once because dye lots differ between boxes.

Under the tile, thinset and grout are sold by weight and depend on the tile size and the joint width. Large-format tile needs a bigger trowel and more thinset, and wide joints eat grout quickly. A shower floor needs a slope of 1/4 in per foot toward the drain, which is a framing and mortar-bed job, not a tile one.

Ventilation is the part people skip. A bathroom of up to 100 sq ft needs about 1 CFM per sq ft, with a minimum of 50 CFM, and a small bathroom with a tub and a shower often wants more. Finish with the paint for a moisture-rated finish and the caulk tubes for the joints where tile meets tub, then check the whole plan against a state-adjusted cost estimate.