Mold-resistant materials offer builders alternative to gypsum

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March 22, 2002

Mold-resistant materials offer builders alternative to gypsum

By Nick Giardino

More and more property owners today are checking out whether mold is present

in their buildings. Some of these existing buildings may have developed a

mold problem over a period of time. This occurs when there is a constant

source of moisture in the building from a leak or from outside sources (e.g.

rain through roof). Mold, which is ubiquitous in our environment, then

begins to grow on building materials such as gypsum board, wood and

wallpaper.

Since mold has a definite odor, a simple walk through the building observing

any visual or signs of an odor, can determine the initial presence of mold.

Talking to the occupants, maintenance, HVAC personnel, builders and

engineers can add valuable information to the visual investigation. In

addition, there are two sophisticated sampling methods, air sampling and

surface (source sampling), which are used to confirm the detection of mold

contamination.

Unfortunately, upon completion of our full mold investigation, there are

situations that a building is not inhabitable because of the severe nature

of the mold contamination. Oftentimes these conditions could have been

avoided. One example is a recent mold investigation at a nearby high school.

This high school had the outer brick and gypsum wall perimeter constructed

on a concrete slab that formed the entire shell of the building.

We cannot be certain how the gypsum board became completely contaminated

with mold, except that it had rained during the construction period and the

gypsum board had not been covered for protection.

Construction

The gypsum board mold contamination was of such a severe nature that it was

recommended to the school board, parents, architect and contractors that the

entire structure be torn down. This mold remediation cost the district

hundreds of thousands of dollars, which did not include the cost of

rebuilding the structure.

This catastrophic event may have been averted in a number of ways. One

preventative measure would be to ensure the gypsum board was covered and

isolated from the weather.

The contractor also could have had the gypsum board sampled as it was

delivered and as the project progressed. Lastly, substitute materials could

have been considered for use in the construction of the interior/exterior

framing wall instead of gypsum board.

There are a great many substitutes for gypsum board which are mold

resistant. The following is a limited list of building materials and their

relative advantages and disadvantages over gypsum board.

Glass-fiber reinforced concrete

Application: As a manufactured product it can be produced in long sections

of repetitive designs or as sculptural elements. Because of its low

shrinkage, it can be produced from forms taken directly from the building.

Advantages: Lightweight, easily installed, good shaping ability, crisp

detail possible, weather resistant, can be left uncoated.

Disadvantages: Non-loadbearing uses only, generally requires separate

anchorage system, large panels must be reinforced, and joints must be

properly detailed.

Precast concrete

Application: It is used for both flat wall surfaces and textured or

ornamental elements.

Advantages: Easily fabricated, takes shape well, minimal shrinkage of

material, can be load bearing or anchorage can be cast in,

expansion/contraction similar to stone.

Disadvantages: May be more moisture absorbent than stone, although coatings

may be applied, small air bubbles may disfigure units.

Fiber reinforced polymers

Application: Fiberglass, a non load-bearing material attached to a separate

structural frame, is frequently used as a replacement where a lightweight

element is needed or an inaccessible location makes frequent maintenance of

materials difficult.

Advantages: Lightweight, long spans available with a separate structural

frame, high ratio of strength to weight, good shaping ability to easily

install.

Disadvantages: Requires separate anchorage system, combustible (fire

retardants can be added); fragile to impact, high coefficient of expansion

and contraction requires frequently placed expansion joints; vapor

impermeability may require ventilation detail.

Epoxy concretes

Application: Epoxy is one of the most versatile of the new materials. It can

be used to bind together broken fragments of terra cotta; to build up or

infill missing sections of ornamental metal; or to cast missing elements of

wooden ornaments.

Advantages: Can be used for repair/replacement, lightweight, easily

installed, good casting ability; forms can be taken from building material;

can be sanded and carved.

Disadvantages: Materials are flammable and generate heat as they cure and

may be toxic when burned; material may be subject to ultraviolet

deterioration.

I advise any potential builder to give careful thought to the choice of

materials and to consider testing the materials for mold on delivery and

during construction. These simple precautions may save your project

unlimited delays and additional costs.

Nick Giardino is senior industrial hygienist with Raba-Kistner Consultants

Inc., a San engineering firm. E-mail him at: ngiardino@....