A Disturbing Trend in Veneer Plaster
A veneer plaster system is a thin coat of plaster, usually 3/32 inch, over a gypsum-based panel. The reason for specifying a veneer plaster is typically to achieve a hard, abuse-resistant monolithic surface. While there are competing products on the market, veneer plaster remains popular for extremely smooth walls without the need for molding trim items to hide the joints of a panel product. Veneer plaster can also be finished in a variety of textures that other systems can only imitate.
The Northwest Wall and Ceiling Bureau has been involved on several site inspections where architects and property owners are concerned about the veneer plaster systems they have specified.
Veneer plaster 101
There are two basic types of veneer plaster systems. The NWCB refers to them often as the residential type and then the institutional/commercial type. The institutional type is very hard, dense and provides a finished surface that has proven to stand up to the everyday abuses common in buildings such as police stations, schools and hospitals. The residential type of veneer plaster is a little easier to trowel to a smooth finish and still provides a finish surface much harder than traditional gypsum board finish. Most designers think of this type of veneer plaster as an upgrade to a conventional gypsum board system. In both systems, architects specify veneer plaster to provide their clients a lower maintenance to the walls. When properly installed, they will get a system that is hard to beat when you consider the service life of a building.
Veneer plaster can be one- or two-coat systems. Two-coat systems use a veneer plaster basecoat that has some aggregate in the plaster. A one-coat system is the finish coat applied in two passes. In essence, both are a two-coat system. (The true two-coat system with an aggregate basecoat is more abuse resistant and allows the plaster crew some additional time to work the material.)
The installation and particularly the finishing of a veneer plaster requires some knowledge, and pretty good trowel skills. In all veneer plaster systems timing is critical. The texture of choice today seems to be a smooth trowel finish. To get the veneer plaster smooth requires a plasterer with good skills and an understanding of the importance with the timing.
There is a small window of opportunity in smooth trowel work to get the plaster smooth. The process is often called "hard" water troweling. This is an appropriate name, as the work is physically hard and requires a true plasterer. Many handymen have thought they could provide a veneer plaster finish-after all, it looks easy when they see it being done. The process is not something you read from a book or watch someone and pick it up. You have to do it over and over, with experienced tradespersons watching over and guiding you along the way.
The idea behind hard water troweling is to bring the "fat" out of the plaster while compacting the surface. The fat is then used to fill small blemishes and voids, sometimes called "catfaces." This process is the key to a good, smooth trowel finish veneer plaster system. Since perfection is not obtainable, plasterers would often have to go back and touch-up minor imperfections after the plaster set and dried.
There is a combination of items that created a perfect storm that has occurred in the world of interior plaster, namely, the creation of lightweight joint compounds and an increase loss of skilled interior plasterers.
Unfortunately, many wall and ceiling contractors and tradespeople may have overstated their abilities to provide a smooth veneer plaster system. Some have resorted to semi-skilled tradesmen to keep up with schedules. This would lead to having trouble achieving a smooth finish, free of trowel marks, voids, catfaces and other imperfections. To make the job "sellable," they often resort to skimming the entire surface with joint compound and sanding the surface to a smooth finish. More often than not, a lightweight joint compound was used for easy sanding.
The practice of skimming the hard veneer with a soft joint compound defeats the primary intent of the veneer plaster in the first place: abuse resistance. The NWCB has done many site investigations over the last few years, where building owners have complained that the veneer plaster simply does not live up to the abuse resistance that is claimed. A multitude of nicks, gouges, scrapes and scratches leave owners upset with the veneer plaster as a system. This would lead designers and building owners to question if they got a specified veneer plaster system. It is often found that there is a veneer plaster under a thin coat of soft joint compound. The disturbing trend is that some of these contractors believe it is perfectly acceptable to skim the wall out with joint compound. A few have gone as far as to state this is an "industry standard" and the way it is always done.
After the wall and ceiling contractor loses his argument, he is then typically faced with how to resolve the problem. In most cases, the minor amount of money they saved during initial veneer installation is eaten up by the remedies now required.
A wall and ceiling contractor should verify that the plasterers he sends out are experienced with veneer plaster. Walls or areas that will be subject to natural or permanent critical lighting will need special attention. A sample wall or room should be completed and inspected by responsible parties prior to continuing. The entire crew should be made aware that it is acceptable with veneer plaster to do "minor touch-up" work with joint compound. This means very minor touch up and not skimming out the wall with this product. The NWCB only recommends setting-type compounds for this work. In no case should lightweight materials-setting or premixed-be used to touch up veneer plaster.
Judging veneer plaster
In defense of contractors that do veneer plaster, some architects and designers have unrealistic expectations. If a contractor is certain that an owner/designer is going to show up on site after the plaster is complete and shine 500-watt halogen lights down the walls, he may feel forced to skim walls with joint compound and sand them perfectly smooth to appease these judges.
Wall and ceiling contractors would be far better off to fight the battle of what is a fair and recommended procedure to judge finished walls. All walls, regardless of the quality, are subject to imperfections in harsh critical side lighting. Fair judging procedures are from four to five feet away from the wall surface, from a standing position and under natural or normal lighting. The deciding criteria should be "eye catching" discrepancies from this standing position. If sconce lights are to be used on the walls, these areas will most likely need additional attention and should get it as they fall under the natural or permanent lighting that is intended.
I have met with designers who believe old plaster walls should be flat and perfect, and with no imperfections. This is simply not true and a walk through of any hospital built in the middle part of the last century will show that while the work is good, it is not perfect.
Failure to adhere to these fundamental rules will result in costly future callbacks and the further decline of interior plaster as designers opt for other materials and/or systems that do live up to their promises. Your crew should feel proud of their workmanship and you should defend it without resorting to skimming out the walls with joint compound.
If you read this article, please circle number 337.