Getting Underlayment Right
September 1st, 2006

by Beth Rogers

September-October 2006

The wrong underlayment can undermine an otherwise perfect installation. Today more and more products are available to meet the needs of every tile and installation challenge.

No matter how beautiful new ceramic tiles may look on the surface, if they haven’t been laid properly, ugly cracks may soon appear that undermine the beauty and integrity of the installation. A whole host of products have been developed to address problems of deflection or moisture in the subflooring or wall that can mar a tile job.

Joe Still, national sales manager of Naples, FL-based Proflex Products Inc., says underlayments are important to “cover up the sins of all the other trades.” For example, workers are on a tight schedule, finishing concrete more quickly than they had in the past. “In the past people actually had time to actually do a good job of finishing concrete,” says Still. “The fast-track schedule has pushed us into mixes that cure quickly but crack.”

FinPan, Inc. of Hamilton, OH, manufactures Util-A-Crete and Pro-Tec concrete backer boards reinforced with fiberglass mesh especially designed for ceramic tile installers. Jeff Ketterer, product manager, notes that the company was one of the first to manufacture backer board: “We’ve been making cement backer board for over 30 years.” He notes that the company now has lots of competition, but observes that Util-A-Crete has been shown by independent testing to be the strongest concrete backer board on the market. The company also has a new line of pre-formed shower pans, shower seats, and shampoo niches. Under ASTM 3272 the product has a 9 out of 10 rating for mold and mildew resistance.

New high-density DensShield Tile Backer from Georgia-Pacific recently passed the Robinson Floor Test with a compression rating greater than 1500 psi which helps ensure that tile floors maintain their integrity over time. Made of gypsum with a vapor barrier, DensShield comes in three different thicknesses. The ¼” is recommended for residential and light commercial countertop and floor applications, the ½” is recommended for residential wall applications, and 5/8″ Type X is recommended for fire rated wall assemblies in commercial buildings.

“Anywhere you install floor tile, such as in a kitchen, bathroom or family room, DensShield provides outstanding strength,” says Leo Bissonnette, national sales manager.

Unlike cement-based boards, DensShield can be scored with a utility knife and snapped without requiring special tools. Lightweight and easy to install, it can be attached to the floor using staples. Incorporating glass-mat facings and a moisture-resistant core, DensShield helps protect the tile installation and subfloor from moisture intrusion and damage and meets the 2006 International Residential Code for use behind tile in wet areas. Georgia-Pacific is so confident of its product that it offers an original owner lifetime limited warranty on any properly applied residential tile installation over DensShield Tile Backer. The combination of moisture and mold resistance, along with potential labor savings, makes DensShield a superior tile substrate for use by tile industry professionals, says Bissonnette.

Akron, OH-based National Applied Construction Products has developed a number of underlayments specifically designed for sound abatement. Pam Zepp, marketing director, notes that the company is working on a sound-abatement system that includes a Homasote backerboard combined with NAC’s SAM3 and Super SAM underlayment technologies in conjunction with an acoustical medium-bed mortar that is currently under development but is expected to be launched later this year.

NAC got its start making anti-fracture membranes. “This company introduced the first thinbed antifracture membrane ever [ECB]. NAC led the market on that. Every other product that’s out there for thinbed anti-fracture came after,” said Zepp. “What’s significant about that is that we have 23 years of installation—we have millions of square feet installed. Another thing that sets us apart is we use a non-reemulsifiable primer which basically means you can’t pull the membrane up—it has a grip to the substrate that is stronger than other membrane systems. We guarantee absolute fusion for life. Our membranes are also formulated with higher rubber content and proprietary fillers to create maximum elasticity. We also offer 3/8 of an inch crack bridging protection and guarantee that for a lifetime.”

Zepp points out that this year, NAC meets the new ANSI spec for crack isolation, A118.12, as well as the new water-proofing spec, A118.10.

Michael Blades, product manager with Permabase, a product manufactured by National Gypsum of Charlotte, NC claims that cement backer boards are the oldest and most versatile underlayment systems. “I think what’s new is that people are starting to realize that all the newer products that have come out since cement board tend to have more limitations and fewer places that you can use them.” As Blades points out, fiber cement and fiber or glass mat gypsum can’t be used in exterior tile applications and not all foam boards are suitable for floors. On the other hand, he says, cement backer boards are a “one stop shop.”

“Certainly some of the newer products have their niches,” Blades admits, “and I think there are consumers looking for certain attributes that newer products may fit well into, but for the day in and day out, particularly for contractors who do bathrooms and kitchens, hallways, counters, floors and ceilings, if they have to go into all those different places—like regular shower versus dry area versus sauna, residential versus commercial….trying to figure out where you can use product A versus product B can be difficult.” With an overwhelming amount of choices, many contractors are choosing to simplify with “something that works everywhere—and traditional cement boards work just about anywhere you can put tile, whether it’s interior, exterior, walls, floors, ceilings, countertops.”

The company did introduce one new product that’s “dramatically” different from its competitors—a ½” cement board that incorporates a fiberglass mesh that bends without being scored or wetted. “We can achieve a 90 degree radius at six inches,” says Blades.

Installing Larger, Heavier Tiles

Blades is noticing an increase in the size and the heft of the tile being used. “Four inch and six inch tiles are really kind of disappearing except maybe in the backsplash area….All the thinset manufacturers are coming out with no-sag mortars, ultra-gripping traction mortars for these larger, heavier tile and stone products.” When working with stone, particularly on vertical surfaces which are subjected to movement, and deflection from heat and cold, notes Blades, “you have to make sure that the backer board is rated for the weight of the material that you’re putting on it.”

Blades says, “We’ve really tried to take a product that’s been out there for a long time and make it as versatile and high performing a product as possible. We believe that while newer products may have come along, at the end of the day, newer doesn’t necessarily make it better. If the old one works, just tweak it.”

Denver-based Protecto Wrap makes a number of protective peel and stick membranes for the construction industry. In its flooring division its staple product is AFM, a 1 mm anti-fracture membrane meant to be used in lieu of products like cement backer board. The thinness of the product makes it convenient, says marketing coordinator Melissa Lucas. “It’s very easy to work with so it saves installers and contractors time because it’s so easy to put down. Because it’s a very thin peel and stick, you can just place it down and then put your thinset directly over top of that.” Living up to its name, Lucas says, “AFM is meant to give a little bit so we actually guarantee that it can withstand substrate cracks of up to ¼” of an inch without affecting the tile. This product is like insurance—you place it down under your expensive tiles or natural stone and you won’t get any shifting or cracking.”

Lucas says that AFM is recommended for stone or tile, but only when used with thinset. She cautions, “If you’re using a product that requires a medium or thickset, then this product is not for you.” AFM can be used on walls, countertops, and backsplashes. Bathrooms are a popular application because AFM has waterproofing qualities.

The company also manufactures “WhisperMat,” an 1/8″ underlayment that incorporates fracture mitigation with sound control qualities. Lucas notes that the product is popular in multi-housing situations to mitigate sound travel and has been used under wood as well as ceramic.

Richard Maurer, director of marketing for the Noble Company of Grand Haven, MI, says the company’s most popular items are shower and waterproofing products such as Chloraloy, a shower pan liner made from chlorinated polyethylene (CPE) that is laminated on both sides with a fiber to help bond the membrane to the substrate. Chloraloy was introduced in 1964 and since then, says Maurer, “We’ve sold millions and millions of feet. People dig it up after 30 years and it’s still like new.” Placed under a mortar bed, Maurer says Choraloy is superior to lead and copper shower pans. It won’t crack and it doesn’t react with water in an alkaline environment. Chloraloy can also be used to waterproof vertical and horizontal surfaces—even ceilings. “We promote the fact that sheet membranes create consistency, regardless of who installs the product,” says Maurer.

More recently, in the 1990s the company developed ProSlope, a shower form made from expanded polystyrene that creates the recommended ¼” slope per foot in shower floors. Traditionally slopes were built up out of mortar beds. “This saves a whole bunch of time,” points out Maurer, who adds that ProSlope is so easy to use even plumbers can install it. Another new offering is ProForm shower niches, also made from extruded polystyrene, which are completely waterproof so no moisture ever comes in contact with wood studs, which can create mold problems. Noble Company’s niche market is growing by “leaps and bounds,” says Maurer.

More options to save time, save money and improve installation

Bob Pritchard, sales and marketing manager with SGM of Pompano Beach, FL, says the most popular of the company’s crack suppression systems is Southcrete 1132, an elastomeric coating that gets painted on surfaces. A gold liquid that is roller or spray applied, Southcrete 1132 serves as an anti-fracture and waterproof membrane and is ready to use straight out of the bucket with no additional mixing. “The beauty of our product is it pretty much takes all the guess work out of anything to do with gauging or mixing and the fact that it can be rolled or spray applied over large areas makes it very attractive—labor costs are minimal,” says Pritchard. The coating can be used on floors and walls both indoors and out and can be used under thinbed or thickbed installations. The product is a viable substitute for sheet-applied or trowel-applied water-proof membranes. “Some sheet-applied membranes are much more expensive and labor intensive because you have to seam the overlap,” points out Pritchard who adds that because Southcrete 1132 is easy to use, it is a popular choice for tile contractors.

The underlayment division of Pomona, CA-based Halex Corporation, makes an engineered plywood specifically for the tile industry, also called Halex. The plywood is made with exterior grade glues so mold isn’t a problem, notes sales manager Charlie Martin, who admits that plywood had lost market share to cement board as an underlayment material but is gaining ground again. He says that’s mainly because thinsets didn’t bond to older plywoods. Now, with new refinements, says Martin, there’s plenty of reason to return to plywood.

“The biggest problem as far as ceramic tile is concerned is cracked tiles and cracked grout and the number one cause of that is deflection in the floor joists and the subfloor,” Martin says. In order to demonstrate that Halex performs better than cementitious panels, the company recently had the Tile Council of North America test its five-ply ¼” Halex which passed the Robinson floor test, 16 inches on center (the seven-ply 3/8 inch passed last year).

Martin believes that Halex is the best solution when it comes to addressing deflection because “there’s nothing stronger than our underlayment in terms of structural strength.” Because of that strength Halex is perfectly suited to handle the weight of larger tiles and stone. As evidence, Martin notes he was doing a demonstration at a trade show with his 3/8″ product and someone who worked for one of his distributors came up and wanted to stand on the demonstration. The man, who admitted to being 365 pounds, stood on the plywood which was sitting 24″ on center. “I was trying to get across how strong this material is—that you can go across 24″ on center and it doesn’t break. He stood on it and it didn’t break and then this other guy who also worked for the company came by, jumped on top, and hugged him. The two of them combined didn’t break the plywood. Whereas if you took a piece of the popular selling ½” cement board it would break under far less weight. It just doesn’t have the structural strength that our product has.”

Martin notes that Halex is perfect for today’s larger scaled homes, many of which have larger spans between joists. He also says that installers like the product because they can install plywood without thinset which eliminates a lot of prep and drying time. Additionally, Halex can be stapled down. “Bingo, you’re done,” he says.

Durock, manufactured by USG of Chicago, is so widely used that the trade name has become synonymous with cement board, just like Jell-O is synonymous with flavored gelatin. Last year, notes Jeremy Verstraete, USG segment marketing manager, the company introduced a lightweight roll-down water-proofing underlayment called Durock Tile Membrane which can be used on top of a subfloor or on Durock. Durock Tile Membrane comes in a 300-square foot roll and is coated with a layer of portland cement on top to create a strong tile bond. The back is a woven material.

Technically, admits Verstraete, one wouldn’t need to use a membrane on top of Durock, but in applications like second floor bathrooms where there are worries about potential overflow this provides additional protection. “It’s a thin product, it can be cut with scissors and applied to the floor,” Verstraete says of the membrane which gets adhered to the floor with a mortar or mastic. “In order to get 300 square feet of any other type of underlayment, think about the enormous amount of labor that is needed to carry that into place. You can get 300 square foot of product on your shoulder. That’s how light it is.”

Schluter®-Systems, a company that originated in Germany, and develops installation systems for ceramic and stone tile, has an “uncoupling” membrane called Schluter®-DITRA that eliminates the major cause of cracking on a tiled surface. Lisa Schwartz, public relations coordinator with Schluter®’s US office in Plattsburgh, NY, says that DITRA “is based on an ancient method of setting tile, which used sand as an uncoupling layer, or forgiving shear interface, within the tile assembly. DITRA provides the same uncoupling principle through its open rib structure, which allows for in-plane movement and neutralizes the different movement stresses between the substrate and the tile.” DITRA is unique from other underlayments because it is multi-functional. It provides waterproofing and vapor management in addition to uncoupling. DITRA’s underside channels provide a route for excess moisture and vapor to escape from the substrate, allowing it to breathe. This function is especially useful when tiling over fresh gypsum and mortar screeds, young concrete, and concrete subject to moisture migration. Schwartz says that DITRA “creates a lasting tile installation in one product” and is lightweight, making it easy to handle and dramatically reducing installation time.

Proflex Products Inc. is a relative newcomer to the marketplace, but one that has captured a lot of attention and business. At Coverings 2006, Proflex introduced Ultimate Sound Control Membrane (USC) and a vapor barrier system, Crack-Free Membrane (CFM). USC is a self-bonding, reinforced, 200 mil-thick engineered elastomeric/cork composite membrane that provides sound reduction, crack isolation, and moisture vapor transmission and helps eliminate breaking bonds due to high Ph(over 9). USC is specially engineered to be used under thinset and mudset mortars and adhesives for interior applications of ceramic tile, stone, brick, and wood flooring, and bridges cracks and controls joints up to 3/8″ wide. When used with Proflex rubber seam tape, USC provides the same protection against moisture vapor transmission as CFM, a 40 mil-thick, elastomeric membrane.

The company’s products may be applied over a broad range of substrates and are fully warranted for up to 3/8″ cracks in finished flooring for a minimum of ten years and up to lifetime based on the system of materials installed. The warranties cover labor and material of up to $9 million per incident. “If a builder wants it, we’ll list them as an additional insured on our policy,” says company representative, Joe Still, who adds that the company has never had a claim filed against it, despite having 100 million square feet of its product installed. “I’ve never seen a cracked tile. We even had one job where a water main broke under a house during new construction, lifted the floor four inches. It was flooded for two weeks. And when it was over all they had to do was repair the drywall because the floor tile stayed intact. They didn’t have a single disbonded or cracked tile or grout joint.”

Another advantage of Proflex, says Still, is that it has a much higher melting temperature which gives it the ability to be installed in temperatures ranging from below freezing to 120 degrees F. Still adds, “Installers love it because when it hits the floor you can reposition it until you put weight to it.” The company offers 24/7 technical support.

As Still notes, properly-laid tile has the ability to last for hundreds, if not thousands of years. Today’s underlayments should do much to enhance the longevity of tile installations.

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