Cork Underlayment Support

No, that may have been the case over 20 years ago when animal protein binders were used, but not anymore. Since the early 1980’s non-water-soluble polyurethane binders have been used to adhere the granules together to make Amorim composition cork products. These polyurethane binders also produce no post installation off gassing and do not leech into ground water supplies. AcoustiCORK products can be totally immersed in water for 30 days or more and show no signs of structural deterioration. 

The short answer is "no." Think of the most common use for cork, wine stoppers. Cork has been used for wine stoppers for hundreds of year primarily because it does not absorb water or liquids. Cork has also been used for years in buoys, lifejackets and other floatation devices, again because it does not absorb water and can remain buoyant for years.  A cubic inch of solid cork immersed in water for 48 hours will gain less than 3% in weight due to water absorption. A cubic inch of solid wood or unglazed clay-bodied ceramic tile would gain many more times this percentage in weight of water if immersed for 48 hours.

Unlike open or even close-celled synthetic foam materials, cork consists of an interlocking structure of 14-sided polygons called tetracadecahedrons. These totally sealed gas filled cells have a very tough outer surface that is almost impossible to break. Because of this unique natural attribute, cork has a compression/recovery rating of close to 100%. Unlike many foam and fiber based products, it will not collapse over time with traffic. The binders used to adhere the granules of AcoustiCORK products together are designed to create a permanent structural bond between the particles.   

Cork does not readily support the growth of molds and other biological agents. Additionally, the granules of Cork used to make AcoustiCORK products are coated with a polyurethane binder, which enhances their natural microbial resistance. 

Cork will not swell, because cork absorbs so little water, it is very dimensionally stable. When exposed to 100% Relative Humidity conditions for 30 days the dimensional change in the grade of materials used to manufacture AcoustiCORK products is less than 3%. In a 6mm thick piece of material this would represent an increase in thickness of less than 1/120 of an inch.