This month I want to start the year by answering a question that comes up often, then take a look ahead at major trends in the plastering world. In addition to writing this column, I also train people in the fine art of plaster repair. I travel to different locations to give instruction, and individuals come in to my location for hands-on training. Of course, not everything can be learned in one visit, so I encourage those I train, as well as readers of this column, to send me questions about projects they are doing if they need help in any way. Quite a few have sent me questions about plastering over drywall.
Q: “I have a newly drywalled ceiling with no paint on it. My customer would like a sand swirl finish applied over it. Is it possible to plaster over a drywalled ceiling, and if so, what is the process and what materials are needed?
Yes, plaster can be applied over a drywall-finished ceiling. Here’s how:
SURFACE PREPARATIONOne of the dangers to avoid is having “pop offs” occur. This happens when drywall has been sanded and dust from the sanding is still on the surface. If the surface is not bonded or prepared in some way, applying a plaster base coat can cause problems. The dust prevents the base coat from adhering thoroughly with the board, usually in a few sections. I’ve seen it happen time and again, and I’ve been called in to do the repairs.
To ensure a proper adhesion to the board, I usually apply a latex bonder. Brands include Thorobond, Plaster Weld, and I even have Plaster Man bonder available (write me for details if you’re having trouble finding such a bonder). Rolling on the bonder seals the board and takes care of dust that might be on the surface.
EVEN FINISHUsing a bonder also seals the drywall compound that is on the seams. These areas tend to be very dry and absorb moisture out of the base coat of plaster that’s applied over it, making for an uneven finish.
APPLYING THE BASE COATAllow the bonder to dry an hour or so, then apply the base coat. Brand names are Kal-Kote, Diamond and Imperial base coat. Apply a thin layer over the whole ceiling. The base coat will have a much higher coverage, sometimes twice as much, than stated on the bag when you’re going over a bonded, drywalled ceiling. Remember that you are skimming a ceiling or wall out with this material. Most applicators get into trouble when they try to build up a thick coat. This is not necessary and actually creates problems in trying to maintain a smooth, even surface.
SAND FINISH COATIn some areas there are pre-mixed sand finish mixtures available in 50- and 100-pound bags. It’s also available in a “slow set” and “fast set” variety. The basic ingredients are autoclaved lime, silica sand and Keene’s cement.
With a bonder sealing the surface and the base coat being put on fresh over it, the sand finish may “sit” on the area awhile before it’s ready to finish out. One tool I’ve found to be very helpful is an 8-inch horse hair brush that has 2-inch bristles. A soft type of brush is best to pull over the surface of the sand. This opens the surface and brings the sand to the top, making for a more uniform and even finish. After this sets, you can then use sponges to apply the swirls into the finish. I recommend using hot water to keep the sponges soft while in use, so that they don’t dig or groove into the sand finish. Cleaning them after doing four or five swirls keeps the sand from building up on the sponges, which creates areas that are sandy and some with less sand. A consistent, even swirled finish is what you’re after.
A LOOK AHEAD• I was recently with Myron Ferguson, That Drywall Guy, in Chicago at the Greenbuild 2007 Conference at McCormick Place. From what we saw, green is definitely “in” for 2008 and beyond. Environmentally-friendly products are popular. This includes plaster materials that are earth-friendly, and at the same time give the customer a wide variety of choices as far as textures and colors are concerned.
• It’s still amazing to me that just when I thought there might be a lull in the creation of new products, the market continues to introduce new and exciting materials and tools that make our life a whole lot easier. I see this trend continuing. This is especially true when I hear contractors are still shying away from wallpaper and are looking for more choices for quality finishes to offer to their clients.
• If you’re thinking of attending a workshop on Venetian-type plaster, keep in mind that many of the companies involved don’t always require you to come to them, but often put on seminars around the country, possibly in your area. Check out their Web sites, and also contact them directly to see if someone from their company will be in your area in the near future. Many companies are eager to train a group, even if it’s small, if they feel you are serious about learning how to use their products.
Let me know what products and tools you’re finding success with. I always enjoy hearing about what you’re doing in the field! You can write me in care of this magazine or e-mail me at firstname.lastname@example.org. Congrats to Mike Heits, who sent in the question in this column. He wins a Walls & Ceilings/Plaster Man T-shirt! To enter, send your name and address to me. Until next time, “Plaster On!”