Healthy Home Basics - Interior Walls

You buy plaster as a powder, mix it with water , then apply it to a surface where it hardens. Once completely cured, the plaster is very inert and rock-like. Although most people can’t detect any odor after a few days, a few sensitive people have said that they’re bothered by a slight odor for a month or so.

In the past, 2-3 coats of plaster were commonly applied on top of thin strips of wood lath. In some commercial applications it’s still applied in a similar manner, but it’s usually put over metal lath instead of wood. However, the most common way to use plaster today involves skimming one or two thin coats over a gypsum-board material. The gypsum board has a blue paper face, so it’s usually called blueboard.

Most of the time, plaster walls are painted. For sensitive people who are bothered by paint, plaster has the advantage of being hard, durable, and scrubbable enough that you can actually leave it unpainted. While most plaster is white, it can sometimes be tinted (before its applied) with the same kinds of mineral pigments that bricklayers use in mortar.

As far as drawbacks, plaster is more brittle than drywall and, if it ever cracks, it’ll no longer be airtight. Plaster costs more than drywall, primarily because of the skilled labor required. In some parts of the country, plaster is widely used. But, in other areas, it’s been totally replaced with drywall.

89. What makes drywall different from plaster?

Drywall is a gypsum-board product similar to blueboard. The chief difference has to do with the paper facing. The paper on drywall is a lower-grade paper made from recycled newspaper. Some sensitive people are bothered by printing ink. As a result, they can also be affected by drywall because the paper contains ink residues. This usually isn’t a strong pollutant source, and paint often seals the paper well enough to prevent it from being a problem. Drywall isn’t as durable as plaster, so it can’t be left unpainted.

The other big difference between plaster and drywall is in how they are finished. With plaster, there’s a thin coating over the entire surface of the blueboard. With drywall, a coating of drywall joint compound (often called mud) is applied over paper tape at all the seams and at nail heads—not over the entire surface. The joint compound typically contains a variety of ingredients, such as the minerals gypsum, lime, talc, etc., plus additives such as antifreeze, preservatives, fungicides, and adhesives. These additives can outgas into the living space more than plaster.

We’ve found while plaster is theoretically more inert, sensitive people often tolerate drywall...