Under Tile Sound Control Adhesives – A More Productive Approach
Article by LATICRETE Australia, Technical Service Manager, Fred Gray
The National Construction Code, amongst other things, specifies the amount of impact sound transmission allowed in various classes of residential buildings. This can influence structure design, the type of finishes that are selected and the nature of how finishes are installed. Ceramic and stone tile are very desirable and sustainable finishes however, one of the negatives is its adverse ability to transmit impact sound into their backgrounds more easily when compared to say carpet, vinyl and other soft floor finishes. So it’s important to know there are acceptable solutions, ensuring tile is a viable option for most of our common substrates.
Almost all tile adhesive manufacturers, market and supply sound control products, mainly for impact isolation attenuation. Many of these impact sound control products can also be used with finishes other than tile. Generally designed to be used directly under tile or tile bedding, these products more often come in the form of mats with varying sound attenuating and system integration abilities. These mats are generally composed of rubber or rubber/cork composites. However, as well as mats, LATICRETE have a sound control adhesive, that amongst other proprietary ingredients, includes recycled rubber.
We can get a little more insight into the attenuating abilities of these mats and adhesives by having them tested in a laboratory in accordance to the relevant standards. From this type of testing, industry professionals can determine if the sound attenuating properties are sufficient to be used in a Performance Approach – Comparison with Deemed to Satisfy systems or other NCC compliant options. For impact isolation the measurements are performed in accordance with the requirements of AS ISO 140.6–2006 and AS ISO 140.8–2006. The performance index numbers, ΔLw and ΔLlin, are generally calculated in accordance with the method specified by AS ISO 717.2–2004, which represent the reduction in impact sound level due to the floor covering materials, when compared to a bare reference floor as in the case of the CSIRO facility, a 150 mm thick slab. The performance index numbers, Ln,w and Ci are also calculated in accordance with the method specified by AS ISO 717.2–2004, and represent the impact sound level measured for the floor system; the floor system being the combination of the floor covering materials and say a 150 mm thick reinforced concrete slab used in the test. The Impact Isolation Class, IIC, can also be calculated in accordance with the method specified by ASTM E989-89, which is also a characteristic of the floor system and a method used previously in Australia and still in other parts of the world.
It is very important to note that the sound attenuating abilities of these mats and adhesives are for the most part not to be relied on to deliver the total impact isolation required by the construction code for tiled floors. They are there to augment impact isolation properties that are already being delivered by the structure and other control measures (the likes of suspended ceilings) as determined by comparison with like known structures or field test. So these mats and adhesives are additional control measures to top up what the structure already provides. So herein lies another important note – structures need to be assessed or tested by very experience people to determine the amount of top up required, if any.
It is just as important to have a complying installation as having the correct sound attenuating product under the tile. Complying with the installation process is vital to ensure everything works as it should. The smallest sound leakage path can undo what would be an otherwise a good installation. So one of the critical focuses during the tile installation process is to have the sound control product installed so any impact sound is contained and directed through the control product rather than directly into the background or substrate.
So when it comes to mats, we should ensure they are laid over correctly prepared surfaces by trained and qualified installers whilst strictly following the installation instructions from the manufacturer. Mats should also be able to provide sufficient compressive strengths and point load abilities for the proposed tile installation. These mats need to be laid, ensuring they are tightly butted with no gaps. Any gaps between the mats are of particular significance, as regular tile adhesive can fill the voids and create flanking paths directly into the floors we are trying to insulate. The same applies to the abutments of the tiling system to walls, columns and the like - isolation strips should be applied against the walls with the floor mats butting to them to stop sound travelling directly into the vertical surfaces – ensuring complete isolation for the tile and tile installation system.
However the LATICRETE 125 Sound & Crack Adhesive does away with the mat underlayment process and some of the inherent installation problems. It allows you to directly bond tiles to the substrate. The time saving and better logistic benefits of LATICRETE 125 Sound & Crack Adhesive translates into significant productivity gains. The new technology has improved performance in sound attenuation, adhesive qualities and crack isolation ability. They have very good point load resistance and are even rated as suitable for heavy duty installations. They allow the tiles to be directly bonded to the substrate. A lot of the same caveats apply during the installation but there is still a need to ensure there are no flanking paths for sound and the tiles are isolated from the substrate and walls, which is much easier with these sound control adhesives.
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