by Dwight Barnett
Scripps Howard News Service
Q: We are interested in having 16x16-inch ceramic tiles put down professionally in an area that is 210 square feet. The area that we want done has an existing vinyl floor. We went to Home Depot and picked out the ceramic tile. The salesman said they do not remove the vinyl, that they put the tile right over it.
He said this was because they do not wish to stir up any asbestos particles in the vinyl. What is your professional opinion about this manner of application? If we are going to spend the money for this type of flooring I want to make sure I am having the proper job done.
--Florida resident
A: If you know for sure the vinyl flooring contains asbestos fibers, then it is indeed best to leave the floor in place and cover it with some other type of floor covering. Attempts to remove the vinyl could release asbestos fibers to the air inside the home, contaminating the air you breathe.
Carpeting, sheet vinyl and some wood floor systems can be installed directly on top of the existing vinyl tiles. But you will need to install a subfloor covering before you install ceramic tiles. The subflooring also provides a firm and level surface that prevents cracking of the tiles and the tile grout. Subflooring such as Durarock, Hardi Board and Wonder board are generally preferred. However, some tile manufacturers recommend plywood.
Here are my recommendations:
- Install the subflooring over a bed of thinset mortar using the flat side of the trowel. The subflooring should be installed before the thinset has set up. The thinset provides a bond to the old flooring and levels out any pockets that might have formed over the years.
- Install the Durarock, Wonder Board or Hardi Board with the rough side up. Plywood does not make much of a difference.
- Some experts recommend nailing the boards at intervals of 6 inches on the sides and 8 inches throughout the remainder of the board. My experience tells me that the nailing pattern should be 4 inches and 6 inches to prevent future cracking. A ring shank nail or a floor screw should be used to attach the subflooring. Do not use staples. The nails or screws used should be long enough to penetrate the subfloor, the old tile and the original underlayment. If the subflooring moves then the tiles will be damaged.
Another problem overlooked by installers is the future movement of the floor system. The subflooring and decking rests on wood floor joists that are set 16 inches apart. There are "loads" (the weight of the home) that rest on these joists and push the joists down, bending them over time. The roof, ceilings, floors and walls all push on the floor system.
When you have an interior wall such as a stair wall or two-story hall wall that rests on the floor, chances are the weight falls in between two floor joists. When this happens the weight of the wall bends the subflooring, causing the tiles to tip up and crack. Extra floor joists or solid blocks called bridging should be placed under walls that are likely to cause damage. It's easy for an experienced carpenter to add the extra bracing.
(C. Dwight Barnett is a master inspector certified by the American Society of Home Inspectors. Questions may be addressed to him at P.O. Box 14091, Evansville, IN 47728, or e-mail dbarnett@evansville.net.)
Resources American Society of Home Inspectors (ASHI)
To locate an American Society of Home Inspectors inspector near you, call or visit the website of ASHI.
American Society of Home Inspectors
Website:
www.ashi.org
The Online Guide For Do It Yourself Ceramic Tile Installation
FloorsTransformed.com
Email:
www.floorstransformed.com/email.html
URL:
www.FloorsTransformed.com
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