By Steve Jordan

	Beginning at the wall's corner, Mike applies the finish coat with a steady hand, careful to keep it at least 1/8" thick. In the end there were no failures at the edges of the old and new materials.

Well, at least the weather was decent. That's about all plasterer Mike Dube and stucco pro Mike Needham had going for them as they considered the task ahead: repairing the badly cracked stucco exterior on the historic Ely house in Rochester, New York. The work would be arduous, given that other repairs over the decades had rendered the walls so cracked that their surface looked like the veins of an orange.

But restoring these gorgeous walls was worth it. The 1837 home, built for mill operator Hervey Ely before Rochester was even founded, is a wonderful example of a temple-front Greek Revival. It also boasts symmetrical setback wings on each side. Today it's well cared for and preserved by the Irondequoit Chapter of the Daughters of the American Revolution.

Like several other fine homes in the area, the Ely house was built with solid, load-bearing masonry walls, which were smoothed with sparkling white stucco. The builders who constructed the home wanted the walls to resemble ashlar masonry—a common alternative to brick, with an external face that's smooth, polished, or even decorated with small comb grooves. The home's false joints were highlighted with black penciling, which is still visible under the columned portico. Over the years, the original stucco was patched, repaired, and painted to hide shoddy repair work.

Cracks—and More Cracks
My familiarity with the Ely home stretched back 15 years, when cracks on a wing built in the 1870s were repaired. A team removed the original stucco—even the sound material—from the stone substrate. Local masons applied a bonding agent to the stone. They then applied expanded metal lath, a scratch coat, a brown coat, and a topcoat of white Portland cement and marble dust. All this work resulted in—failure. Hairline cracks snaked in every direction across the surface.

The stucco and metal lath were removed, and the walls were then finished with a softer mix of lime, marble dust, and Portland cement deemed more compatible with the substrate. These walls have generally held up well, although the bond of old-to-new stucco still shows hairline cracks. The walls may not have held up so well if it weren't for the protection of an ample roof overhang and lower porch.

Repair Tip: Keep Your Eye on the Finish

The great thing (all right, some might say the painful thing) about working on a complicated stucco repair job is that we learn something almost every step of the way. For example, past repairs on the Ely house included attempts to thinly skim coat material over deteriorated areas and efforts to join old stucco to new without adequately removing enough of the old stuff. The bottom line: Whether applied over old or new stucco, the finish coat must be at least 1/8" thick to bond to the underlying material. Also, when joining new stucco to old, the new plaster shouldn't be feathered in. The existing material must be cut back to provide a right angle or back angle for an adequate bond.

A New-Old Approach
Realizing that the past repair work hadn't held up particularly well, the homeowners and their consultants decided the past could offer some clues about the stucco's longevity. So, they sought a mason familiar with historic stucco techniques. Enter Mike Needham, who teaches plastering and stucco methods to local union masons and is familiar with old lime mixes. Needham thought the Portland cement was the reason previous repairs had failed. He suggested applying a lime stucco mix—without Portland cement and bonding agents—similar to the original material that held for more than a century. Plasterer Mike Dube and his son, Lucien, also joined the project. Dube wasn't familiar with lime stucco techniques, but he was willing to dive in and learn a little something.

The original plan was to clean and score the surface, make a few repairs, and then apply a new finish coat over the old. Dube and his son devised an ingenious solution for scoring the old material. Their tools: a vacuum-assisted sander and a carbide-tooth sanding disc. While one man sanded the wall, the other sounded out areas searching for loose material that needed to be removed.

But this good work led to a revelation: Making a few repairs to the wall and applying a new finish coat wasn't going to work. Too much material was falling off, and once we started removing material, it was hard to stop.

Smart Mix
As I mentioned, the weather was perfect for repairing stucco: cloudy and not too hot. So, we got to work on applying the scratch coat, a 3-to-1 mix of medium sand and slaked (hydrated) lime. Since this meant mixing dry sand with wet lime putty, the lime was proportioned prior to adding the water to ensure the 3-to-1 mix. Before applying the scratch coat, the wall was slightly dampened to prevent the dry substrate from sucking the moisture out of the new material before it could cure properly. This coat was allowed to dry for three days, and because the weather was ideal, we didn't have to mist the surface to maintain dampness. And the really good news: hairline cracks didn't appear in the surface. We also didn't see any failures at the edges of the old and new material. The brown coat mix was identical to the scratch coat, but was much easier to apply—and again, we saw no cracking in the finish.

The finish coat was a 3-to-1 mix of fine sand (equal proportions of #2 and #3) and hydrated lime that was slaked a few days before we used it. Although the home's original stucco boasted a beautiful tannish/yellow appearance, scoring the surface revealed that the original color was bright white. So, naturally, we chose brilliant white sand for the final coat. This mixture didn't trowel out as smoothly as the original mix, but materials similar to the original weren't available in our area. But lack of materials has never stopped a determined crew. So, Needham and Dube drove three hours to purchase the perfect sand.

When the finish coat was applied, it set up more quickly than we anticipated. Keeping a wet edge across the wall was difficult and forced Needham and Dube to work at a brisk pace. When they stopped, the material was terminated squarely in line with what would be the simulated mortar joints. These lines corresponded to the lines on the adjacent walls where they would join the old to the new. (Obviously, since the crew was repairing one wing at a time, the original faux mortar-joint lines were still visible. So, Needham and Dube simply joined the horizontal joints on the adjacent walls and carried the markings around the wing with a line level. And the vertical joints? They approximated the spacing of those the remainder of the house.)

The original joints were applied after the stucco had significantly hardened—but not completely. A hard tool was dragged across the surface using a straight edge and level as guide creating the indented joint. The surface was not scored, and no material was removed.

Unfamiliar with this technique and concerned that the wall was setting up too quickly to apply the joint, Needham and Dube decided to create the joint with the edges of their trowels, first scoring a line and then smoothing out the loose material with a trowel. They moved the tool up and down from the horizontal lines and side to side on the verticals. This significantly slowed their progress, but the results were impressive. For the next two days, we periodically misted the walls to prevent premature drying. Both Needham and Dube were happy with their work, and the homeowners were ecstatic. Still, the repair duo looks forward to refining their techniques on the home's next large wall. Always planning ahead and thinking about the details, Because the finish appearance is a slightly courser than the original, Dube says the team will consider using all #2 sand for the next job and add marble dust to the mix. This way, the finish will look more compact.

If you walk by the Ely house today—more than six months after the project—look at the repaired walls. You won't find a single crack.

The DAR membership would like to thank the Corn Hill Neighborhood Association for the generous grant that made this work possible.