Deflection is how much a floor flexes under load. L/360 and L/720 are the two limits used to judge whether that flex is acceptable — L/360 for most finish floors, L/720 for tile and stone. The check that comes before tile is a deflection calculation, not just a flatness check, because a floor can be … Read more
A floating floor sits on top of the subfloor, locked to itself but not glued or nailed down, so it can move slightly as the house moves. A bonded floor is fixed permanently to the subfloor with adhesive or mortar. The choice is not a style preference — it is decided by the material, the … Read more
An uncoupling membrane is a thin plastic layer, usually a grid of small square cavities, installed between the subfloor and the tile. It lets the tile move independently of whatever is underneath it, so small cracks, seasonal shifts, and the different expansion rates of wood and tile don’t transfer upward and split the grout or … Read more
3/16 inch over 10 feet is a flatness tolerance. It means that if a 10-foot straightedge is laid across the subfloor, no gap under it should exceed 3/16 inch at any point. It shows up in warranty language because most flooring problems attributed to a bad product are actually the floor underneath moving more than … Read more
Lay a rigid ten-foot straightedge on the floor, slide a set of feeler gauges or a tape measure under it at several points, and record the largest gap. Move the straightedge to a new spot and a new direction and repeat. The largest gap found anywhere is the floor’s flatness number, and it decides what … Read more