U.S. General Services Administration
Technical Procedures Disclaimer
Prior to inclusion in GSA’s library of procedures, documents are reviewed by one or more qualified preservation specialists for general consistency with the Secretary of Interior Standards for rehabilitating historic buildings as understood at the time the procedure is added to the library. All specifications require project-specific editing and professional judgement regarding the applicability of a procedure to a particular building, project or location. References to products and suppliers are to serve as a general guideline and do not constitute a federal endorsement or determination that a product or method is the best or most current alternative, remains available, or is compliant with current environmental regulations and safety standards. The library of procedures is intended to serve as a resource, not a substitute, for specification development by a qualified preservation professional.
Rewrite
We’ve reviewed these procedures for general consistency with federal standards for rehabilitating historic buildings and provide them only as a reference. Specifications should only be applied under the guidance of a qualified preservation professional who can assess the applicability of a procedure to a particular building, project or location. References to products and suppliers serve as general guidelines and do not constitute a federal endorsement nor a determination that a product or method is the best alternative or compliant with current environmental regulations and safety standards.
This standard includes general information on the characteristics and common uses of cork tile and identifies typical problems associated with this material along with common causes of its deterioration.
Introduction
Characteristics of cork tile:
- A natural wood product
- Made from the ground outer bark of the cork oak tree
- Light weight
- Porous
- Physically resilient and chemically inert
- Good insulation properties
- High compressive strength
- Low thermal conductivity
- Expands and contracts with temperature and moisture changes
- Moderately expensive
- First manufactured in the U.S. in 1899.
- Originally, cork shavings were fused together using asphalt; the use of natural binders replaced this method when John Smith patented a process to melt cork resin under high heat in1892
- Combination of intense heat and pressure enabled cork shavings to be fused together without a glue or binder were generally sold unfinished; finish was provided by the customer after installation, generally consisting of sanding and waxing
- A factory finish was available in the late 1920s
- Phenolic resin and urea resins were later added to strengthen the cork tiles
- Colors included three natural shades of brown - light, medium and dark; color variation depended on the time length for baking and the temperature used during that time; the greater the temperature and time baked, the darker the tile
- Available in 3/16” or 1/2” thick; typically square, oblong or rectangular
- Originally, a wide range of sizes were available, but eventually became standardized; most common sizes included 9”x9” and 12”x12”
Typical Uses
Typical historical uses for cork include:
- Bottle stoppers
- Corkboard for insulation
- Commercial/institutional flooring in schools, libraries
- Public lobbies, churches, courthouse courtrooms, auditoriums,
- Hospitals and museums
- Residential flooring
- Armstrong Cork Company was one of the largest manufacturers of cork tile
- Commonly laid over a concrete floor and secured with nails to
- A fibrous layer of asbestos concrete and waterproof mastic
Typical current uses for cork tile include:
- Commercial/institutional flooring in schools, libraries
- Public lobbies, churches, auditoriums, hospitals and museums
- Residential flooring
- Commonly glued to the subfloor using a mastic or an elastic
- Waterproof cement
Natural or Inherent Problems
- Moisture: excessive moisture or damage can result in deterioration of the binder, causing the cork composition to loosen and eventually buckle - more common with wax finished tiles
- Fading: exposure to sunlight and ultraviolet rays can result
- In fading, brittleness and drying of the cork
Vandalism or Human-Induced Problems
- Abrasion: surface abrasion, including scratches and gouges, can occur when the surface finish becomes worn, such as in high-traffic areas; the accumulation of dirt and grit in these gaps and pockets further contributes to the deterioration process
- Staining: high porosity of cork makes it very susceptible to staining
- Unsuitable cleaners and solvents can cause deterioration of the cork; some include ammonia-based or sodium hydroxide-based
- Cleaners, organic solvents, abrasives, and caustic cleaners