Development of “Total Flex Method” Sharply Improving Separation Prevention Performance of Exterior Finishing Tiles

—Tests confirm durability for fifty years of use—

September 18, 2012Takenaka Corporation

Takenaka Corporation (President: Toichi Takenaka) has developed the“Total Flex Method”to improve the separation prevention performance of exterior tiles over those applied using mortar (below referred to as “mortar method.”)

When using the normal mortar method, mortar for surface preparation is used to smooth irregularities of the base surfaces. Then, mortar is applied so that tiles adhere to the base. We have developed a surface preparation material with greater elasticity than mortar (elastic surface preparation material “Bond Level One”) in cooperation with Konishi Co., Ltd. (President: Tomoo Omaru). Combined with adhesive with greater elasticity than mortar, this “Bond Level One” achieves superior separation prevention performance.

※“Bond” is a registered trademark of Konishi Co., Ltd.

  • Mortar method

  • Total Flex Method

Comparison of the mortar method and “Total Flex Method”

【Merits of the method】

1.Superior durability and seismic safety

When the mortar method is used, tiles, mortar and the concrete body which constitute the exterior wall are subjected to temperature and humidity fluctuation from outside, expanding and shrinking them at different rates. This is called “differential movement,” which causes repeated strain on each layer’s adhesive, resulting in the separation of tiles and mortar over the years.

The surface preparation material, “Bond Level One,” and the tiling use adhesive used for this method are materials with good elasticity. As a result the durability of this method is superior because it is highly resistant to separation caused by differential movement. Even when a structure is shaken by an earthquake, it resists cracking or separation of tiles, achieving seismic safety superior to that possible with the mortar method.

Testing done to evaluate the elasticity of this method has confirmed that its performance is three times that of the mortar method, showing that it very effectively prevents tile separation.

2.Remains attractive for many years

The tiles resist cracking for far more years than those applied by the mortar method because they are executed with highly elastic material. The exterior wall also remains beautiful for many years, because mortar is not used, permitting only a little white soiling (efflorescence) caused by cement.

3.Ensures stable product quality

Using the mortar method, it is necessary to mix water and cement on site, so the work is susceptible to the effects of the level of skill of the workers and of the working environment, but using this method, the material is removed from its package and used as it is, so it does not have to be mixed on site, ensuring stable product quality.

4.Shortens work periods

When using the mortar method, in order to prevent separation, it was necessary to spray the surface of the concrete with super high pressure cleaning water for example to chip the surface, thereby ensuring that the mortar adhered firmly, but with this method, chipping is not necessary. Also, because it is possible to prepare the concrete surface faster than when using the mortar method, the exterior finishing work period can be cut by between two weeks and one month.

Takenaka has already used this method for six projects and will expand its use to buildings it constructs in the future.

【“Total Flex Method”procedure】

1. First the concrete surface is washed with water.
2. The newly developed elastic surface preparation material, “Bond Level One,” is applied to smooth the irregularities on the wall surface.
3. After the tiling use elastic adhesive is applied on top of “Bond Level One,” the tiles are placed on top of the adhesive.
4. Finally the joints are filled.

Comparison of the mortar method and “Total Flex Method”

【Results of durability testing】

Takenaka performed a variety of tests of the “Total Flex Method” at the Takenaka Research and Development Institute, confirming the durability of exterior walls made by the method. The elastic ground preparation material, “Bond Level One,” was continuously exposed to a temperature of 80℃, confirming that it has adequate strength and elasticity to remain durable for fifty years.

Strength and elasticity of “Bond Level One”confirmed by 80℃ thermal degradation tests

【Background to the development】

Tiling using organic adhesives has been used on interior walls since the 1950s. Because problems such as separation and cracking rarely occurred, the same method was introduced to tile exterior walls of buildings in the 1990s, and its use has spread. Its adhesives were standardized under JIS A 5557(Exterior Tiling Use Organic Adhesives) in 2006, and in July of this year, it was added to standard specifications JASS19 (Ceramic Tiling Work) written by the Architectural Institute of Japan. It is expected to come into even wider use in the future as a construction method providing high separation prevention performance of tiles applied using organic adhesives.

But even when tiles were placed using organic adhesives, generally mortar with poor elasticity has been spread to smooth irregularities on the concrete surface. So it was feared that even when tiling is done using highly elastic adhesives, adhesive tiling could not demonstrate the maximum separation prevention performance.