ggpk Tile Floors July 09th, 2018 - 18:16:55
Does the floor feel bouncy? If so. it is. Trust your instincts. It`s not ready for tile. A well built subfloor feels very stiff underfoot. Squeaking can also be a bad sign. but it may also solvable by screwing down the planks or plywood better into the joists.
What`s the property owner`s risk tolerance? Does he/she want to be rock solid sure of the stability of the floor? Even if that means spending extra money and/or time to reinforce the floor. and accepting a floor that may sit higher than surrounding floors? Or is some risk of failure acceptable if the floor is not built to the righteous standards of the TCNA? Sometimes the extra effort is not worth the cost to the property owner. who should be fully informed on all options. Contractors who install flooring shouldn`t assume that clients don`t care enough to solve the problem: in the last year we`ve had two clients who spend thousands of extra dollars to reinforce subfloors in a kitchen and laundry room when we explained that their floors were too unstable for tile. They really wanted tile. and were willing to make the subfloor ready for it. even if it cost more.
There are formulas used in the industry to determine if the subfloor has excessive `deflection` [bounciness. lack of rigidity]. The most cited one is the Tile Council of North America standard for deflection. which is stated as L/360 as a minimum. before tile underlayment is installed. L/360 means that the floor should not bend under weight more than the length (expressed in inches) of the unsupported span divided by 360. For example. if the span between supports runs for 20 feet then the deflection should not be more than 2/3" between the center and the end. L=20 x 12" = 240". L/360 = 240"/360 or 2/3". So 2/3" is the maximum amount of movement the center of the span should be allowed to move.
For tile to be successful. it needs rigid support. with very little tolerance for movement. The more rigid the substrate. the better chance the tile has of remaining crack free throughout its life. Most problems with tile floors over wood come from excessive `bounciness` of the substrate. Carpet can handle some bending. vinyl tile can flex and bend a bit. hardwood floors can bend a little too. but if tile or stone is subjected to forces that push in 2 different directions at once. it doesn`t know how to bend. Instead. it cracks. first in the grout and then in the body of the tile. Consumers who have just paid thousands of dollars for a tile floor do not find these cracks appealing. to say the least.