Sanding Vinyl is a Recipe for Disaster
It'll ruin your tools and your new tiles, expert says.
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Q: I have a 9-year-old townhouse with resilient vinyl over plywood floor in the kitchen and laundry. We are tired of this floor and would like to install 13-by-13-inch ceramic tiles. Can I install the tiles over the sheet vinyl?
If so, I assume I should screw through the vinyl to secure it to the plywood, trying to set the screws into the floor joists below the plywood and then rough up the vinyl surface with a sander to improve the adhesion of the setting mastic.
What are my options for setting the tiles, i.e., using a thin-set mastic or mortar? Am I heading for disaster leaving the vinyl in place?
A: Sure disaster. For one thing, you'd gum up the sandpaper faster than you can read this line trying to sand vinyl.
In addition, vinyl is soft and compressible, which will crack the tiles even if you apply a heavy layer of thin-set mortar.
What you need is a stable surface on which to rest the tiles. To do this, the vinyl needs to be removed.
Next, check the size of the floor joists and measure the span (the distance from one end of the joist to the other). All wood floor joists will sag just a little near the center of the span. The deflection should be no more than the span in inches divided by 360, represented as L360.
With this knowledge, ask the tile dealer how much deflection the tile will take. Skip that; I can tell you: none. You need to strengthen the floors before installing the tiles.
Install sheets of Wonder Board or Durarock, applying the smooth side down using thin-set mortar and a quarter-inch notched trowel.
After the sheet is installed, nail in place using a broad-head, stainless roofing nail long enough to penetrate the sheathing, vinyl and subfloor, and then penetrate at least three-eighths of an inch into the floor joists.
Nail the sheathing every 4 to 6 inches, 4 inches along the borders and 6 inches on the remainder of the sheathing.
If you choose to use screws, get as large a head as you can so that the screw does not puncture down too far into the sheathing. Install these one at a time, making sure to remove any mortar that "smooshes" out from under the board.
To cut the sheathing you will need a special saw and blade, which are available at construction rental supply houses. Wear eye protection, gloves and a tight-fitting painter's mask. You don't want to breathe the stuff that comes off the sheathing. Use a fan set behind you to blow the dust away and work outside to get the fresh air you'll need.
Because the sheathing is expensive, you can use the smooth side up for small out-of-the-way areas. Don't throw away what you can use. Measure twice and cut once. Mark your cuts using a permanent marker. Chalk lines and pencil lines disappear when you start dry cutting with the diamond-tipped blade. Install the tiles according to the manufacturers' recommendations.
(Dwight Barnett is a certified master inspector with the American Society of Home Inspectors.)