Making Old Stucco Look New, continued

The foam adheres surprisingly well. I was once installing a long run of trim and someone bumped the transit while I was eating lunch. We set the trim to what we thought was a level line, and it wasn't until the next day that we noticed it was off. The trim was harder to remove than you might imagine. We had to saw it off and use a grinder to remove the glue and remaining bits of foam.

We usually apply foam, then allow the adhesive to cure overnight. The trim will come off the wall while the Foam Tite is wet, but it's rock-solid once the adhesive cures.

The next day, we apply fiberglass mesh tape to the trim. The mesh reinforces the surface and holds everything together. Precoated trim is already covered with mesh, so we have to tape only the joints. With raw foam, we cover the entire piece and span the joints (Figure 6).

Figure 6. Joints between pieces of trim are reinforced with fiberglass mesh (left). A layer of Foam Tite is then applied over the mesh to fill voids and bond the pieces together (right).

If there's a big gap between the trim and the wall, we'll tape that joint too. After the mesh is in place, we go over it with a layer of Foam Tite. This fills in the weave and bonds the mesh to the trim. Once the adhesive sets, the wall and the individual pieces of trim are effectively a single unit (Figure 7).

Figure 7. This sill and casing (left) have been glued to the wall and joined with mesh and Foam Tite. On this house, the trim will be the same color as the wall (below), but it could just as easily receive a different finish.

Prepping the Walls

It goes without saying that the wall surfaces should be structurally sound. If there are holes or cracks, they have to be fixed first.

Cracks. We repair small cracks by spanning them with strips of fiberglass mesh tape and "painting" over them with a masonry bonding agent. There are many bonding agents on the market; we use a product called Multi-Bond (Carson's Coatings). It's somewhat flexible even after it dries, and it has a tenacious bond. If you put this stuff on a window, you could plaster over the glass and it would not come off.

This method is fine for repairing minor cracks that result from settling or earth tremors. It will not work on cracks that are caused by underlying structural problems. There's no point even thinking about stucco until the structural repairs are made.

A good bond. The walls should be clean before you apply color coat. We power-wash the wall with plain water to prepare it. It's possible to put color coat over previously painted stucco, but it requires extra prepwork.

When I first started plastering, there were subs who would sandblast the paint off existing stucco buildings. This produced an excellent substrate, but it was incredibly messy and posed an environmental hazard because of the old lead paint. Nowadays we use a power washer to clean the wall and knock off any loose paint (Figure 8).

Figure 8. Color-coat stucco will readily adhere to an existing layer of the same material. This wall is being power-washed to remove dirt that would inhibit the bond.

Once the wall is dry, we coat the entire surface with bonding agent. This ensures the color coat will stick, and it glues down any loose paint edges. It's not cheap: A five-gallon bucket of bonding agent costs about $100, plus there's the labor to put it on. We do it because it's better to spend a little extra on prep than to hear from a customer whose finish coat is peeling off in spots (Figure 9).

Figure 9. Painted stucco should be coated with a bonding agent before color coat is applied. This wall has never been painted, so bonding agent is not required, but the author's crew applied it anyway as a "belt and suspenders" measure.

Uniformity. A color coat has no trouble adhering to a brown coat, Foam Tite, or an existing layer of color coat. Still, there are times when we will put bonding agent on these surfaces. One of the hardest things about applying color coat is controlling the actual color you get. If the substrate is not uniform, certain areas may cure darker or lighter than others. For example, the junction between existing stucco and a newer patch may show through the color coat because one area of wall has more suction (is more absorbent) than another. If you want uniform color, you need to apply the color coat to a uniform substrate. One way to even out suction is to coat the entire surface with bonding agent (Figure 10).

Figure 10. This wall was coated with a bonding agent to equalize the suction between the existing color coat and areas that were patched when the windows were replaced.

Color and Finish

The customers may know the color and texture they want, but unless they do stucco work, it's impossible for them to describe the finish. So I usually ask them to point out a nearby building that has the color or texture they want. I'll then make color and texture samples to try to reproduce it.

Texture. Many different textures can be created when the finish is applied. There are pebblelike dash finishes, smooth float finishes, and a variety of lightly or heavily textured trowel finishes. We try to produce the finish the client wants. I point out that heavily textured finishes will collect more dirt and grime than smooth ones, but that irregularities in the frame are less likely to show through a textured finish.

When I started plastering, customers expected a very uniform finish, so that's what we strove to create. Nowadays it's popular to do a more irregular "old world" finish. Many of my customers want their homes to look like ancient Tuscan villas. It took me a while to become comfortable with this type of finish because it's against everything I learned as a young plasterer.

Color coat is usually applied with a trowel (Figure 11). Every plasterer has a slightly different "hand," so it's hard for two guys to produce identical texture. I try to have the same plasterer do all the color coat on any given wall. That way, any transitions will happen where the customer can't see them.

Figure 11. Here the author creates a skip-trowel finish by applying a second layer of color coat over a partially cured layer of the same material.

Finish Materials

A traditional finish coat is made from portland cement, hydrated lime, sand-sized aggregate, and various additives. We use LaHabra's Exterior Stucco Color Coat (714/778-2266; www.lahabrastucco.com). The only things we have to add to it are water and pigment, usually one box of pigment per bag of stucco. The finish material we use is available with either white or gray cement. We choose the type of cement based on the color we are trying to achieve.

It's very important to mix consistent batches of material. We always mix enough color coat to cover entire sections of wall. Adding a little bit more or less water can alter the color of the cured material. You don't want to run out of color coat in the middle of a wall because the next batch could be subtly different. This is less likely to show if you change batches at the natural break points in the wall (Figure 12).

Figure 12. Each batch of the finish coat should be large enough to cover an entire section of wall. The wheelbarrow of colored material (left) will provide enough material to cover the uncoated wall to the left of the completed section in the photo at right.

Acrylic finish. Acrylic coatings can be used in place of traditional portland cement color coat. The acrylic products I use come premixed (including liquid and pigment) in five-gallon buckets. The material is factory-mixed so the color is very even. It's also very flexible; it will span small cracks. The best thing about acrylic is that it's available in darker, more vivid colors than you can get with conventional color coat.

I don't push acrylic finish because, unlike traditional color coat, it is not permeable to moisture. It doesn't happen in every case, but I have seen buildings in which trapped interior moisture caused paint or acrylic coatings to pop off.

Durability Questions

One problem with conventional foam-based trim is that it's not very impact-resistant. The foam is soft, and since the color coat is not very hard, it doesn't take much force to dent the trim. It's a bad idea even to lean an extension ladder against windowsills and casings. There are certain subdivisions in this area that restrict the use of conventional color-coated foam. They might allow you to use it up high, but not down low where it's likely to get dinged. This problem is especially common around garage and entry doors.

One option is to use cast-concrete moldings (Figure 13). It's also possible to apply full, three-coat stucco over foam or wood blocking. The finished casing will be as thick and strong as the surrounding walls. This method was popular at the beginning of my career but died out in the 1980s because it was too labor-intensive to compete with EPS trim. The most cost-effective solution is to use foam but to coat it with a harder material such as faux stone.

Figure 13. Cast-concrete trim is produced off site and delivered ready to install (left). It's very heavy, so it must be mechanically fastened to the wall; note the metal straps that extend from the edge of the pieces (right).

If a client is concerned about damage, we'll typically use our faux stone product. We had a sample of our "stone" material tested, and it was impact-rated at 2,600 psi. It's not as tough as cast concrete, but it will stand up to just about anything short of a baseball bat or hammer. Don Thorvund has been in the stucco trade for more than 20 years and is the owner of TNT Plastering in Fremont, Calif.