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February 06

Underlayments
Underlayments
 
   As an installer, when I see any tile installation, I will instinctively size up the amount of labor involved to complete the work. Whether it be a large open space like the produce dept. of a grocery store, the aisles of a clothing store, the common spaces of a shopping mall, or the refined labor involved with creating personal spaces in residential settings such as kitchens, bathrooms, foyers and fireplace surrounds.
 
   Secondly I think of what is not seen, what is UNDER the tile. Underlayments may be too broad of an article title to cover well and completely, but I'll tackle it and give you my perspective on our industries offerings of different products and methods used to get our tile installed.
 
   I'll begin with the most basic underlayment known to the industry, one that has been expounded on over and over throughout the ages, and continues to live and thrive today, the MORTAR BED. Arguably the best way to have your tile installed is with a mortar bed. Typically a mortar bed is crafted with sand, cement and water, possibly some lime. Used as a floor application, a common way of installing a mortar bed would be with a slip sheet underneath, usually 15lb felt paper, diamond mesh metal lathe is laid over the paper and the mortar recipe is packed and screeded over the lathe. These floors by specification are about 1 1/4" thick before tile is installed and can weigh approximately 13lbs per sf (1). Many installers will pack screed and smooth the entire floor and allow the bed to dry overnight, and install their tile upon a dried bed using thin-set mortar. Another popular way is to ' WET-SET ' tiles into the fresh mortar bed using a portland cement based slurry to coat and bond tiles to the fresh mortar. There is a similar way to install wall tile with a mortar bed known as ' MUD ' or floated mud. The same felt paper is used over open studding and also the lathe, then a ' scratch coat ' of mortar is ' floated ' and usually allowed to dry. Then a ' plumb coat ' of mortar is placed and screeded smooth creating a plumb, flat, and strong surface for tile. There is an extensive amount of labor involved with the mortar bed floor or wall installations and to reduce the labor impact a new product was developed called ' CEMENT BOARD ' .
 
   Cement board came on the market, as I understand, in the early 70's spawning a new era in the tile industry. This cement board made of portland cement, aggregate and fiberglass mesh was produced in 1/2" thick, 3' x 5' sheets, and as you can imagine transported a heck of a lot easier than sand and cement can be. It also installed in less than half the time, and weighing in at around 3lbs per sf (1), a heck of a lot lighter. A typical floor installation would begin with a clean, structurally sound subfloor, the cement board would be cut to fit, laminated to the floor with thin-set mortar and nailed or screwed down. Cement board has come a long way from it's beginnings, and manufacturer's continue multiply and expound on the original materials, sizes and installation methods. Today, there are probably 13-15 manufacturer's of cement board or ' backer board ' some of which do not have a cementitous core but foam. Foam is increasingly becoming a new wave of our industries future. Many if not all of the manufacturer's of foam based products include complete shower systems, the components can be used for flooring as well.
 
   Another classification of loor underlayment is the ' UNCOUPLING MEMBRANE ' introduced by Schluter Sytems around 1987 again, spawning a new era in the industry.
 
Many installers and consumers prefer this type of installation because of the many functions this new product ' DITRA ' performs. First, uncoupling the tile assembly from the structure. Secondly, waterproofing the structure from the finished space ( bathroom, laundry room, kitchen ). Thirdly, vapor management. This charachteristic of Ditra allows for tile installation to begin over new or ' green ' concrete as soon as tradesmen can walk on it. Lastly, load distribution, because of the design of Ditra's ' open-rib ' there is solid support under the tile assembly linking the assembly to the structure working with the high compressive strengths of the thin-set mortar used to install the tile, thus supporting heavy loads. I have had the opportunity to visit the independent laboratory where various testing is done. The Robinson Floor Tester was there and demonstrated. On the test, Ditra produced ratings of ' Heavy ' and ' Light '  allowing Ditra to be used for installations including shopping malls and automotive showrooms. (2)
 
   Other types of flooring underlayment are plywood ( with special material specifications and installation methods )and self-levelling underlayments.
 
   As for my perspective, all of the mentioned products and system I have mentioned are a vibrant part of our industry today, and the contractor who decides well ahead of time to dedicate themselves to any one particular type of underlayment can be limitting their own success. I have installed all of these types of systems except the floated wall mud method, and one day a particular project may come along where a client either wants that type of installation or really needs it. I like to select the best possible product / system or combination of products for each project although I do have a favorite with Ditra.
 
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