Q: How does one refresh a stucco surface? Can it be painted? If, so with what and how?
A: Let’s start with the assumption that the surface in question is bare stucco, the real deal, portland cement plaster. Let’s also assume that it is in relatively decent condition that minor point-up can restore to an esthetically acceptable surface. Unless the existing stucco is some hideous color that is no longer available or cannot be obscured by any other means, I would first suggest considering the application of a colored fog coat in lieu of painting.
A fog coat is a preparation consisting of the ingredients of the final coat of stucco without the aggregate (sand, etc.); that means basically portland cement and the colorant. There are ready-mixed fog coat products available in a variety of colors on the market that only require the addition of water. Adding a little water creates a paste-like material that can be use for patching up cracks with a trowel or brush; more water reduces the viscosity to a workable material for applying with a brush, roller or sprayer. Doing an Internet search for “colored fog coat” will provide plenty of information on the products and procedures available.
But if the fog coat won’t do the trick for some reason, painting is an option, although it turns a low-maintenance surface into a regular-maintenance surface. If the surface is already painted, it is the only viable option (ideally the existing coating is a known quantity and a recoat using the same material after proper preparation is all that is needed). Most paint manufacturers offer a line of paint products that are formulated for stucco and other cementitious surfaces, and those products are the most likely choice for a re-paint, although a test patch over an existing painted surface to ensure adhesion is always a really good idea. These are generally alkali-resistant, chalk-binding, breathe-able, latex/acrylic products. The primer is probably the most important of the products and ideally possesses all of the just mentioned attributes, and in a re-paint situation, must adhere to the existing coating. The finish coat needs to be compatible with the primer and should breathe well enough to allow any intruding moisture out of the stucco without issue. Most of these products can be either spray- or brush- and roller-applied. Some will suggest that spray-applied products be immediately back-rolled, a procedure best done by two people: one operating the spray gun, the other operating the roller.
As with any paint project, 80 percent of the effort should be in the preparation of the surface. It should be clean (free of mildew, dirt, peeling paint and any other material that could prevent the primer from properly adhering to the surface), sound (all cracks filled, loose material removed and patched and allowed to cure) and completely dry before the first brush of paint is applied.
Q: There are now several glass mat gypsum panel products available for interior surfaces. How should they be prepared for decoration?
A: This, in some respects, is disputed territory due in no small part to the fact that there is more than one variety of glass mat being used to face the different makes of panel, and more than one method for attaching the mat to the gypsum panels. In other words, some glass mat-faced panels are relatively smoother than other glass mat-faced panels, and consequently some panels are more readily decorated in a variety of finishes than others.
In some cases, a heavy-duty commercial wallcovering will be used to finish the glass mat panels, and chances are the wallcovering can be applied over a properly taped surface and satisfactorily obscure the surface irregularities inherent in such a system. In some instances, a flat paint may also serve the purpose. But high-traffic areas are just as likely to be finished with a paint product that is intended to provide some durability, which means there’s going to be some level of gloss or sheen.
A quick survey of the manufacturer product sheets reveals that several manufacturers refer the reader to GA-214, Recommended Levels of Gypsum Board Finish, which basically says that any finish with any kind of sheen should be applied over a skim coat of joint compound (i.e., a Level 5 finish), or a product specifically designed for the purpose of achieving a Level 5 finish by some other means than a trowel application, to ensure that the profile of the surface is uniform and that the porosity of the board and the taped joints is essentially the same. Other manufacturers recommend a test panel to determine whether an additional skim coat is necessary to smooth the surface out and, if necessary, to apply an additional skim coat.
However, a June webinar presented by Terry Kastner, technical consultant at the Northwest Wall and Ceiling Bureau, recommended applying a proprietary Level 5 product over the skim coat called for in GA-214. When asked whether a second coat of joint compound for a skim coat would suffice, Kastner answered that a second skim coat of joint must also be sanded prior to the application of a finish, and therefore could result in revealing the texture of the glass mat, which would not go undetected when painted, particularly under extreme lighting conditions.
This topic is still under discussion by the producers, so stay tuned for further developments.
Lee G. Jones is AWCI’s director of technical services. Send your questions to [email protected], or call him directly at (703) 538.1611.
