How to Install Venetian Wall Plaster and Chair Rail MoldingUpdated: Feb. 14, 2023
Decorate a room with Venetian wall plaster and a urethane chair rail molding
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Step 1: Overview
The same room after the makeover
The solution: Venetian plaster and urethane chair rail molding
Maybe you’ve decided that red bedroom walls just aren’t you. Maybe you think your 2-year-old could have sponge-painted better than the previous owners. Whatever the case, if you’re ready for a new look in your bedroom, bath, dining room—or just about any other room in the house—we’ll show you how to redo it in a weekend with two simple projects.
The first is a new decorative wall technique called Venetian plaster. Once a difficult project tackled only by pros, Venetian plaster is now easy to apply in a simple multi-step process. With this solid-color product in a can, you can add a rich visual texture with highlights and shadows. It’s as simple as patching and painting walls, and inexpensive, too.
The second project is an easy-to-install urethane molding that you can cut with a handsaw (no power miter box necessary) and then glue and nail to the walls. The molding is a durable product with the crisp details and shapes you’d expect from solid wood, but it’s a lot easier to work with.
Step 2: Getting started with Venetian plaster
Before you start, choose a color from the brochure available at your home center (or go to the company’s Web site if the product isn’t available locally). The supplier will mix and blend the colored plaster just like ordinary paint so it’s ready to use right out of the can. Don’t be fooled when you open the can and see just a solid color. The subtle color differences you see in the final job are part of the process of applying, sanding and tooling the plaster.
Prep the room just as you would for any paint job by cleaning walls and filling holes. Mask the areas you don’t want painted such as around windows, doors and baseboards. You can plaster over any paint that’s sound, but if the paint is glossy or semigloss, wipe it down with a deglosser (available at paint stores).
You can create a two-color wall like ours or use the Venetian plaster product from floor to ceiling with dramatic effects. If you want two colors, paint the top first and allow it to dry so you won’t drip paint on the Venetian plaster below. When figuring the proportions for a wainscot, keep in mind that it’ll look best about one-third of the way up from the floor to the ceiling. You can go a bit higher up the wall, but keep from going as far as halfway up. This will divide the room into a distinct top and bottom and look odd.
With the room prepped, mask off the wall just above where you’ll be plastering. Measure up from the floor in several locations and mark a level line with a straightedge. Use a 2- to 3-in. wide strip of tape so you can stroke freely and not be tempted to make smaller strokes at the top. Also, open a window in the room. Although this product has very low odor, adequate ventilation is necessary until it dries.
Step 3: Trowel it on
Photo 1: Modify a drywall knife
Round the corners of a standard 5-in. drywall knife to prevent the tool from digging in.
Photo 2: Work from a drywall pan
Transfer the Venetian plaster mix to a drywall pan so it’s easier to scrape the excess off the knife. The plaster is a bit thinner than drywall compound but thicker than paint.
Photo 3: Spread the plaster
Apply the colored plaster mix with your drywall knife in random strokes back and forth at about 45 degrees to vertical. Avoid heavy buildup.
When you’re at the home center, pick up a drywall mud pan like the one shown in Photo 2 to hold the colored plaster while you’re spreading it on the wall. The long top edges have a sharp rim to wipe your drywall knife clean. Also buy a 5-in. flexible drywall knife to spread the product on the walls. You could use a 4-1/2 in. or a 6-in. knife instead, with slightly different effects. I found it helpful to practice on a scrap of painted drywall to get the hang of it. Your home center paint department may also have small boards available to practice on.
Before you start, sand the corners of the drywall knife to round them slightly to keep the tool from leaving sharp ridges and digging into the wall. Start applying the plaster to the wall in a corner and work your way along the wall as shown in Photo 3. Don’t try to do the whole wall in one coat.
You’ll find it easiest to trowel an even coat on a 3- to 4-ft. section with your knife at a sharp 15- to 20-degree angle and then go back and do random strokes with the knife, alternating left to right and right to left. You’ll see the original color of the wall show through on the first coat but this is good. If you don’t see some of the wall beneath, you’re putting the plaster on too thick. After each 6-ft. section, stop and examine the wall. Tool any section with heavy ridges and even it with a clean trowel before it dries, then move along.
Step 4: Fill the voids with the second coat
Wait for the first coat to dry, from two to four hours, then apply the second. Load your knife and fill in the voids with strokes of your knife. Repeat the randomness of the first coat and the combination of the two coats will add up to a great-looking, varied texture later. Hold the drywall knife at a bit steeper angle, at least 45 degrees to the wall.
Look for the spots where the first coat didn’t cover and apply plaster in those areas. Again, after each 6-ft. section, go back and check your work, making sure the wall is adequately covered and the wall color behind doesn’t show through. The plaster should be about 1/8 in. thick in the thicker areas and thinner elsewhere, so judge your job accordingly. Remember, the finished job will have more visual texture than actual texture.
You’ll find that outside corners can build up quickly, so try to keep them as even as the rest of the wall. If the plaster is too thin, you can always go back and dab corners with a small paintbrush later. When you’ve finished the room, let this coat dry for 24 hours before moving to the next step. The job will look a bit sloppy at this stage, so don’t be disappointed. The final steps will bring the walls to life.
Step 5: Sanding and burnishing create a visual depth
Photo 6: Sand the plaster
Sand the second coat with 400-grit sandpaper once it has dried (24 hours) to remove heavy ridges. Each area the size shown needs about one minute of vigorous sanding. Rub down the entire surface with clean, dry cotton cloths.
Photo 7: Burnish the surface
Pull the knife briskly over the surface in long, bold strokes to smooth the high spots and create a luster as well as darken areas to develop contrast and character.
Sand the walls with 400-grit sandpaper clamped into a stiff-rubber sanding block (Photo 6). Just fold a full sheet into thirds and then put it into the block. As you sand (wear a dust mask), you’ll see the character in the finish develop as the foreground appears lighter and the background stays a bit darker.
Keep sanding until you get a uniform appearance. Don’t worry about sanding through the plaster finish, because the paper is very fine. Change sandpaper as the sheets wear out or clog. You’ll need about four sheets for an entire room. Wipe all the sanded areas with clean, dry cloths to remove the residue and then vacuum the floor and sanded areas with the brush attachment.
Now it’s time to burnish the surface (Photo 7) with your steel drywall knife. Start anywhere, holding the knife at about a 30-degree angle to the wall. Pull the knife blade along the wall firmly with long, bold strokes. The direction isn’t particularly important; just be sure you go over each square foot of wall several times.
The high spots of the thin texture will get a bit darker and polished as you move along the wall from one end to the other. You’ll start to see three distinct levels of color from the background to the foreground. Once you’ve finished the wall, remove the masking tape slowly and get ready to apply your chair rail molding.
Venetian plaster is available in gallon containers, which cover approximately 150 sq. ft. for the two coats shown. You can choose from more than 20 stock colors to fit almost any decorating scheme. For our project, we chose Italian Cypress. For added durability in high-traffic areas, you can apply a water-based polyurethane topcoat.
Step 6: Urethane chair rail and moldings
Photo 1: Widen the miter box, if necessary
Hand miter boxes and fine-tooth hand saws are best for cutting urethane moldings. The moldings, however, are often wider than the miter box bed. Widen the bed by removing the screws on the side of the box and adding a wider base. To widen your miter box as shown in Photo 1, use a hammer to tap the sides free of the original base. Drill pilot holes and screw the sides to the new base. With the wider base, you’ll be able to crosscut and bevel-cut the moldings. However, the other miter operations won’t be possible, since the precut slots will no longer line up. This won’t be a problem for cutting the moldings we show here.
Photo 2: Cut the moldings
Measure the length, then cut the moldings with 45-degree bevel cuts in the corners and glue the backsides and joints with polyurethane molding adhesive.
Photo 3: Nail the molding
Glue and nail the moldings to the wall. Make small reference marks along the wall with your level to make sure you keep the molding straight as you nail. Set the nails with a nail set.
Urethane moldings are both lightweight and easy to apply, making them a great alternative to wood molding. In this story, we used them for chair rail and window trim.
The manufacturer recommends cutting the molding about 1/4 in. overlong for long runs (12 to 16 ft.) to help make up for seasonal wall expansion. It’ll compress slightly and snap into place. Shorter lengths to 8 ft. should be cut about 1/8 in. overlong and anything less than 4 ft. should be cut to fit. The company also recommends butting crosscut ends together when splicing long lengths instead of bevel-cutting moldings at mid-wall joints. The molding is applied just like wood molding except that it cuts and nails easier.
Set the molding into your miter box (screw the miter box down to your sawhorse or work table) and cut it on your mark with slow, steady strokes as you hold the molding firmly with your other hand. Support long ends with additional sawhorses. Don’t bother coping joints in corners; just lay the molding on its backside and cut at 45 degrees for inside and outside corners. Nails alone won’t do—you must use the polyurethane adhesive caulk to bond it to the wall surface to make up for its low density.
Fill nail holes with spackling compound and then wipe the surface clean with a damp rag (Photo 4). This process will take two coats. Sand urethane molding as little as possible because unlike wood, the factory finish on the urethane molding is thin. Because you’ll be painting the molding, you can touch up joints with acrylic caulk and wipe the excess away with a damp rag. You can save yourself a lot of time by prepainting the molding and then touching it up after you’ve cut and installed it.
Buying Urethane Moldings
Home centers and lumberyards carry a limited selection of urethane moldings. A large selection of moldings are also available online. They come in a wide variety of preprimed profiles and sizes for windows, doors, crown moldings and decorative panels. They’re expensive but cost less than decorative wood moldings with the same profiles. To see all your options, go to the help desk. There you can order moldings to suit your taste. The moldings shown here are only a small sample.
Required Tools for this Project
Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.
- Caulk gun
- Dust mask
- Miter saw
- Mud pan
- Nail set
- Putty knife
- Sanding block
- Taping knife
Required Materials for this Project
Avoid last-minute shopping trips by having all your materials ready ahead of time. Here’s a list.
- 400 grit sandpaper
- 6d finish nails
- Acrylic caulk
- Painter's tape
- Polyurethane construction adhesive
- Spackling compound
- Urethane molding
- Venetian plaster