Moisture and Mould Resistant Gypsum Products in Hospitals

By: Douglas C. Gehring

Indoor air quality (IAQ) is always a top concern in hospitals, as impurities found in the interior air of these buildings can be detrimental to the recovery processes of medical patients.

One of the biggest threats to IAQ in hospitals is the growth of mould in wall cavities and on interior wall surfaces. According to Health Canada, the inhalation of mould spores can cause minor symptoms, such as headaches and respiratory congestion, among otherwise healthy people, and more serious symptoms among those with existing health problems. Studies have shown that some airborne moulds can cause severe infections in people with leukemia or AIDS, as well as transplant recipients and those with other conditions that weaken the immune system.

Mould growth is often a result of tiny mould spores from interior air coming in contact with interior surfaces dampened by extended moisture exposure. This moisture can come from a variety of sources, such as exposure to precipitation during construction, plumbing leaks, and uncontrolled condensation. As long as moisture and oxygen are present, mould can grow and feed on virtually any organic substance, such as the cellulose found in wood studs and traditional paper-faced gypsum board.

Fortunately, all of this can be avoided through good design and construction practices that prevent the exposure of moisture to building products and the specification of moisture and mould resistant building materials.

Moisture and Mould Resistant Gypsum Board

Originally, all gypsum board products were paper-faced and therefore a potential mould host if exposed to moisture for an extended period of time. In recent years, however, gypsum board manufacturers have expanded their product lines to include many new enhanced versions of non-fire-rated and fire-rated Type X gypsum board panels with enhanced moisture and mould resistance.

Most common are paper-faced gypsum boards treated with bio inhibitors – chemicals that prevent the growth of mould whenever moisture is introduced to the facing. Some manufacturers also now offer paperless interior gypsum board with moisture resistant fiberglass facings instead of paper. The technology used to develop paperless gypsum board is similar to the technology used in manufacturing performance-proven moisture resistant gypsum exterior sheathing products.

Since mould spores can travel anywhere, it is wise to specify moisture and mould resistant gypsum board for all areas of the building where potential for moisture exposure is high, such as kitchens, washrooms, basements and laboratories. Due to the vulnerability of medical patients, specifiers in hospital projects may consider recommending moisture and mould resistant gypsum walls for the entire building. A mould resistant wall assembly is not complete, however, without the proper finishing products.

Moisture and Mould Resistant Finishing Products

One common error made by wall and partition contractors is using conventional ready-mixed joint compound and paper tape on an otherwise mould resistant wall assembly. This compromises the gypsum board’s moisture and mould protection at the joints. Conventional ready-mixed joint compound is not mould resistant, and paper tape has the same potential mould problems as untreated paper-faced gypsum board. Manufacturers of moisture and mould resistant gypsum board, however, have addressed this concern by developing mould resistant ready-mix joint compound with bio-inhibitors. It is appropriate to use paper joint tape with this joint compound, as the tape will absorb the compound’s bio-inhibitors and then become mould-resistant.

Another option for mould prevention is using a plaster-based setting compound. Setting compounds offer more moisture resistance than ready-mixed compounds and are recommended for use in all climates by the Gypsum Association (GA) 236-00, Joint Treatment Under Extreme Weather Conditions. These compounds should be paired with moisture resistant fibreglass mesh joint tape that is self-adhesive and mould-resistant.

For the strongest resistance to mould growth, specify gypsum boards and finishing products that meet the mould resistance rating of 10, per the ASTM D 3273, Standard Test Method for Resistance to Growth of Mould on the Surface of Interior Coatings in an Environmental Chamber, test method; or a mould-resistant rating of 0, per the ASTM G 21, Standard Practice for Determining Resistance of Synthetic Polymeric Materials to Fungi, test method.
A Healthy Conclusion

Designing a hospital to achieve high IAQ is crucial to the health of the medical patients occupying the building. High IAQ creates the purer, more comfortable interior environment needed for the recovery process. By combining moisture and mould resistant gypsum board with proper moisture management design for wall assemblies, building and design professionals can protect patients of hospitals from mould exposure and help guide them toward a speedier recovery.

This article was written by Douglas C. Gehring, P.E., CSI, the director of marketing & technical services with CertainTeed Gypsum. He be reached at Doug.Gehring@saint-gobain.com