Installer Briefing: We Are Thinking About Remodeling, Can We Tile Over…
March 1st, 2005


March-April 2005

By Dave Gobis

Succeeding at installing tile in renovations requires more work on your part, but it can make you the “go to” company. Those of us in the tile business love to hear that question.

The statement is near and dear to the hearts of us all who sell construction products and services. Residential sales of ceramic tile have driven the market higher every year since World War II. Ceramic tile continues its higher percentage of growth against other floor covering products in the US and this trend is expected to continue. In our current unprecedented new housing boom, remodeling continues to hold a substantial (or some would say equal) share of that residential market. However challenges to keep expanding that market are growing.

The skill set for sales and installation of products in renovation projects differs from those needed for new construction. In new construction things are relatively straight forward. The installer can readily see how the floor or wall was constructed and readily select the appropriate materials for the job based on those observations.

This is not the case in remodeling projects. X-ray vision would be most helpful in analyzing the make-up of the structure and successive layers of flooring. Unfortunately, we do not have that option; we have to do it the old fashioned way—search and discover. Equally unfortunate, many ceramic tile salespeople and installers do not search and discover, hence the start of unforeseen problems and eroding profits as you try to correct an inappropriate installation.

Successful and profitable renovation work requires substantially more knowledge and skill than typical new home construction. Professional estimators, contractors, and installers up to the challenge are often difficult to find. Most installers in new construction prefer to avoid dealing with the unknown factors of renovation.

Remodeling is where the money is at for contractors and installers. Historically in my company, our remodeling margins were double that of new construction projects. While this is not always the expectation from the sales side of the equation, having knowledgeable people on staff and the availability of contractors or installers to do the job can make you the “go to” place for that market. That in turn allows for increased sales and better than average margins. Remodeling projects typically use higher end products and are more material intensive than new construction.

So what can you do to either join or grow in this lucrative area of the market? Educate, search, and discover! Like anything else, the rewards are commensurate with the risk taken. There is much you can do to enjoy the market and protect your profits. Someone once told me you make all your money when you get the sale or job, the challenge is to keep it.

Common renovation pitfalls

First and foremost, however, the structure needs the ability to support the tile installation. In my days of estimating it never ceased to amaze me that very few of my competitors ever looked at what was supporting the floor or examined the structure of the current floor system. One typical call we receive time and again at the Ceramic Tile Education Foundation (CTEF) is from an installer after the tile has cracked on a job. When we ask what the span of the joist, spacing of the joist and floor panel thickness is, we hear a long, silent pause on the other end of the phone followed by “how am I expected to know that” or “I don’t know, couldn’t tell.”

There is not a floor out there whose make-up can’t be determined by some means. Some are more work than others. The simplest solution is to examine the floor from an unfinished basement or crawl space below it. Another solution is to use a stud finder.

The most basic requirement of any tile installation is support. If we have a concrete structure, we are fortunate; there is no question of support if we are slab on grade. However, in most areas of the country we use wood construction including second stories in slab on grade construction. All wood framed structures are not automatically adequate to support ceramic tile.

Building code requires that the floor joist support structure meet L/360, which coincides with the tile industry recommendation. However, from a tile industry perspective, L/360 applies to the entire floor, not just the joist (See March/April 2004 TileDealer). There is no rating system in the wood industry that rates deflection of the wood panels between the floor joists as we do in the tile industry. Installation recommendations relative to panel thickness come from the tile industry using the Robinson Floor Tester (ASTM C-627). All panel thickness recommendations are a result of this test.

The proper method of installation needs to be determined by the supporting structure. The overwhelming preference of all manufacturers is a structure that has 16″ centers. This provides a good base for subfloor panels. Most new homes today use engineered floor joists. The largest manufacturer of engineered floor joists also recommends 16″ centers for tile areas. If the spacing between the floor supports is 19.2- or 24-inches, there are numerous methods that can be employed successfully listed in the Tile Council of America handbook.

While it is always important to follow manufacturers’ instructions, it becomes critical at 24″ centers. Floors with such wide spacing leave very little if any margin for installer error. In general, if you have a 2×10 floor joist, the maximum unsupported length can be 16 feet, a 2×12, maximum length of 18 feet.

Engineered floor joists are much tougher to judge. It takes an engineer to make the calculation. There has been little study in determining what the maximum length of an engineered joist can be. What study has been done resulted in a recommendation of 16″ centers and a maximum length of 27 feet.

To determine subfloor and underlayment(s) thickness, go to the heat vents. Gas lines and refrigerator lines work well too. If necessary, drill a hole to determine total thickness. The minimum thickness for a subfloor panel to receive a backerboard is 5/8″ for ½” boards and ¾” for 5/16″ or ¼” boards under industry standards. Membrane systems typically require ¾” subfloor on 16″ centers, but requirements vary by manufacturer for 19.2- and 24-inch centers. Subfloor panels should be tongue and groove. If they are not, which is not uncommon in some areas, the seams must be blocked between the joists.

In remodeling we often discover multiple layers of underlayment and flooring material. Of course we would remove any carpet, but what about layers of vinyl or hardwood? What if there is pressboard or two layers of ¼” luan and sheet vinyl? This is where experience counts. Different systems come with different risks.

We have now reached a point in the sale where the manufacturer wants to sell a product, the distributor or store wants to sell it for them, the installer wants a job, and the customer wants a floor. The decisions made here will have a great impact on cost and how to proceed. Removing existing underlayment affects cost and may add environmental concerns. There is no clear right and wrong in many instances, so it truly becomes an issue of risk assessment.

So let’s take a look at some “what if” situations

The opinions expressed from here on are based on my experience and that of my employees over almost three decades. They do not reflect any industry position. Please note, I did not say all were successful, they were not. There is a learning curve to success in remodeling, and I paid for some of my training with trial and error just like everyone else. The purpose of creating the following conditions is to create a thought process, not make a specific recommendation.

Installing over layers of vinyl

The customer wants ceramic tile and has a great support structure, but there are two layers of ¼” underlayment with sheet vinyl. From the vinyl side of the flooring business, the vinyl manufacturers wouldn’t be all that excited to put another layer over that assembly, too compressive. If existing conditions are too compressive for vinyl, they are certainly the same for tile. Cover with a layer of backerboard? I think that would make a bad situation worse, and I would anticipate some cracked tile or grout. Every successive layer adds to the problem. The old layers really need to come out. You cannot nail all of the compressiveness out of the floor, especially with an air gun, which is commonly used today.

What about the potential for asbestos in the sheet vinyl? A local environmental lab can answer that. If it does contain asbestos, the laws of your state apply on how the removal needs to be done. There is no way to avoid this issue. A single layer of luan with sheet vinyl is still a bad idea and removal would be a good idea. Two layers is way too much risk. Do yourself a favor and let your competitor do the job. If you are contemplating a stone floor, you positively need to go all the way back down to the subfloor.

Tiling over sheet vinyl

This residence has ¾” tongue and groove sub-floor with a 5/8″ plywood underlayment and sheet vinyl. Can you tile over the sheet vinyl? Any setting material manufacturer will say certainly with our super duper thinset. The conditions: make sure the floor is firmly bonded (many are not), cleaned and de-glossed (requires scrubbing the floor), fastened correctly (different requirement for fasteners when using ceramic tile as opposed to sheet vinyl), and of the non-cushioned variety. The last one is really tough because almost all modern floors have a certain amount of cushion. How much is too much? You are entering a very gray area.

If the floor has a heavy texture, it is probably too much. Ideally, the sheet vinyl should be removed. Completely removing the floor and the adhesive along with environmental concerns can make that a challenge. In many cases estimators gravitate to installing a tile underlayment over the sheet vinyl. Depending on the compressive nature of the floor, this is not a bad idea. Too much compressivness will result in cracked joints at the panel edges at a minimum. Bonding directly to the sheet vinyl product would be my last choice. In the event you make that choice, double the initial cure time before you get back on the floor to grout. Bonding porcelain tile to sheet vinyl is a very bad idea in my opinion and certain to fail at some point if the floor is not properly prepared. Never use mastic over sheet vinyl with porcelain tile under any condition.

Installing ceramic tile over hardwood floors

The residence has hardwood floors, but the customer wants tile. As usual, it would be best to remove the floor and get back to the basic structure. But, depending on how it was installed, removal can be serious work. Most installers prefer covering the floor with a tile underlayment. This is a tough call; most wood floors tend to cup with seasonal changes, and in some areas the cupping is much worse than others. If cupping has been a problem, the floor should be removed. If the home is acclimated year around that helps some, but then the concern is moisture coming from the basement, crawl space, or slab. If the floor is on sleepers over a slab, I would not hesitate to remove it, though there may be some elevation issues in that case. Covering the wood is certainly going to alter the ability of the wood to breathe. As you can see, there are a lot of “what if’s” to this condition.

Tiling over a vinyl tile on a cement slab

The customer says it’s time to up-grade the basement or slab on grade kitchen that currently has vinyl composition tile bonded to the slab with black glue. This can be trouble with a capital T. First, from an environmental perspective, not all tile or black glue contains asbestos. Many types of glue did have some fiber as recently as 1985. VCT tile stopped a few years before that. If removal is considered, have the tile and adhesive tested by a local lab. Removal requirements vary by state, and if this material ends up in a dumpster, be prepared to have the documentation in hand.

Other than environmental concerns, the caution here is how the adhesive is removed. Liquid adhesive removers are not a good option, unless you have the ability to neutralize and flood rinse the floor several times. Adhesive removers attack polymers and these are the same polymers that we would be using in thinset to install the tile. Mechanical removal is preferred. There is power equipment available to remove adhesive down to the opaque layer manufacturers desire. You cannot sand glue, because heat reactivates adhesive and gums up whatever you use for sanding.

Once again, while removal may be preferred, it may not be possible for environmental or economic reasons. The preparation is then the same as for sheet vinyl type products. The downside of tiling over vinyl tile in slab on grade applications is altering the vapor emission of the installation. It may have been there for 50 years and never exhibited any problems, till it was covered. On wood installations an underlayment is desirable. The cleaning prep may trap moisture in the vinyl installation and then be covered with tile causing the floor to release. Depending on the nature of the tile, backerboard underlayment may fracture the tile when they are fastened making for a crunchy walk across the floor when the job is done. The thinset will mute the problem till it is dry.

Renovation with ceramic tile is a never ending subject. I have tried to touch on the more common issues we deal with at CTEF on a daily basis. There is no clear right or wrong way with installation issues in renovation. If you would like to hear more on renovation or have interest in other installation related subjects for a future issue, please submit your ideas or questions to the editor.

David M. Gobis, a 3rd generation tile setter, is the Executive Director of the Ceramic Tile Education Foundation. He has been in the trade for over 30 years and owned a successful contracting business many years prior to his current position. Mr. Gobis is a member of the NTCA Technical Committee and the American National Standards for Ceramic Tile Installation (ANSI A108 ) and TCA Installation Handbook committees. He can be reached at 864-222-2131 or © 2005 Ceramic Tile Education Foundation

Leave a Reply

You must be logged in to post a comment.

Foster and Clark Real Estate
CTDA - Membership
CTDA - Online Education