Perimeter movement joint

Are today's homes being built for tile?

Over the past few years the tile and stone industry has seen a number of changes related to both products and construction trends (See Table 1). Some of these trends have had a profound impact how tile and stone need to be installed.

Today's kitchens often function as a meeting or entertainment area. There is also a trend towards higher end appliances and center islands which function as new work areas and therefore use stone tops. Likewise, master bathrooms are getting bigger and have many more features. It is not unusual to see whirlpool tubs, skylights, radiant heat, walk-in closets and dressing rooms as well as work out/exercise space contained in this portion of the home.

In addition to the general trends in home construction, we have experienced a great number of new products used to either construct the home or used as finishes. Traditional construction methods were based around dimensional lumber and spans in traditional lumber framed structures seldom exceeded 14 to 16 feet. Everyone was familiar with the construction and pretty much knew what to expect. Today, with the advent of engineered wood products, homes are no longer limited by the capacities and length of traditional lumber structural elements. Spans that weren't dreamed of just a few years ago are now common in today's construction practices.

The industry has moved a long way since the primary floor joists were dimensional 2-inch-by-10-inch or 2-inch-by-12-inch construction. The choices today are almost too vast to list, ranging from various open web trusses to I joists of varying chord widths and depths. On top of these choices, one has the option of 16-inch o.c.(on center), 19.2-inch o.c., or even 24-inch o.c. support options depending on the engineering needs of the structure.

The number of choices available today for tile and stone has also grown nearly exponentially. From porcelain body tiles, glass tiles, to composite tiles and a wide range of natural marble and stone products from nearly every part of the globe, not only are the numbers of choices expanding but the size of tiles has steadily been increasing. Not long ago, an 8-inch-by-8-inch tile was considered a large tile. In today's market tiles in the range of 16-by-16 inches to 24-by-24 inches are becoming more common and tiles exceeding three feet in size are already available.

The impact of all these changes has to be recognized and we can't put our heads in the sand or rely on our experiences during the past 30 years and still have successful results. When homes get larger in scale and utilize larger spans with wider joist or truss spacing, we need to assure ourselves the engineering is correct in terms of anticipated use, all live and dead loads, deflection or floor stiffness, and the newest factor being discussed, radius of curvature. As tile and stone materials become denser in nature and become larger in scale or size, the installation materials and methods may need to be altered from years past.

With the strong potential for increased floor movement either along the span or between the supports depending on spacing options, all tile and stone installations need to make some accommodation for movement joints. The Tile Council of America recommends a movement joint where tile work abuts restraining surfaces such as perimeter walls, dissimilar floors, and where changes occur in backing materials. They also recommend movement joints in the tile work every 8 to 12 inches in each direction when the tile work is exposed to moisture or direct sunlight for interior projects. And with the addition of radiant heat in many parts of the country, consideration needs to be given to these installations as well. In many cases, the manufacturers of the radiant heat system may require that a crack isolation membrane be incorporated in to the tile or stone installation. In regard to the more dense tiles being produced today like many of the porcelain, glass or composite tiles, most manufacturers are recommending either a premium latex/polymer mortar or a two-part latex modified mortar to meet the increased bonding and flexibility requirements these types of installations present.

From the construction point of view, determining the accompanying dead loads associated with these finishes, stone topped counters and center islands, and the use of either high end appliances or bath fixtures becomes increasingly more important when selecting the engineering for the floor supports. With the direction many homes are going, the traditional use of 10 psf (pounds per square foot) for dead weight needs to be increased to 25 or 30 psf in many cases to accommodate how homes are being finished. Another consideration is that not all tiles have the same ability to flex or bend without showing signs of distress. For instance most stone tiles require the floor structure to be twice as stiff as what was traditionally required when ceramic tiles were 12-by-12 inches or smaller.

In summary, this great expansion of new building materials and finishes allows us to create homes in ways we could never imagine only a short time ago. As more buyers want to incorporate all these features into their dream home, the more we will have to make the proper accommodations in construction details to sustain the continued growth in home sales we all desire. TILE

Table 1: Changes in Products and Construction Methods

• Increased size of homes with more open spaces

• Bigger and more elaborate kitchen spaces

• Larger mater bathrooms with walk-in closets

• Increased usage of tile, marble and stone

• Increased size of tile formats (12"x12")

• Increased popularity of porcelain, glass, and other dense bodied tiles

• The use of radiant heat

• The use of more engineered wood products

• The desire to speed up the whole installation process