The eye-catching art-deco Asheville City Building in Asheville, N.C., is an iconic landmark for the town of about 83,000, nestled on the western edge of the Great Smokey Mountains.
The building is listed on the National Register of Historic Places.
Unfortunately, it leaks.
It leaks so badly, the 7th and 8th floors are now unoccupied. That’s no reflection on the building. The Asheville City Building (1928) is 83 years old, and at that age, without a little specialized attention now and then, is entitled to leak.
The city, to its credit, is giving this splendid old building that attention now. Consulting engineers Sutton-Kennerly & Associates, with offices in Greensboro, Charlotte, Asheville and Wilmington, N.C., and Birmingham, Ala., is heading up the effort.
The project is still in the planning stages, according to Zeb Wells PE, an engineer at the firm’s Asheville Office. Part of that planning is a systematic analysis of the building’s troubles, including learning how and how much the masonry, terra cotta and marble fabric admits water.
To get an idea of what they were up against, Mr. Wells said, the company called on specialty facade restoration contractor Masonry Preservation Services (MPS), Bloomsburg, Pa., in July to run ASTM C1601 Standard Test Method for Field Determination of Water Penetration of Masonry Wall Surfaces.
The testing is part of an overall pilot phase MPS is conducting to prove effectiveness of planned repairs and establish standards of quality, said Erik Valentino, architectural engineer and building envelope specialist in charge of field testing at MPS.
The non-destructive test method involves attaching a 12 square-foot pressurized test chamber to the masonry and cycling .68 gallons of water per minute from a top-mounted spray bar through it, with air pressure of 10 pounds per square foot. This keeps a running “sheet” of water on the wall throughout the test. The difference in the volume of water at the test’s beginning and end indicates how much water penetrated the wall.
The test simulates a storm dumping 5.5 inches of rain per hour on the wall with 62.5 mph winds.
The wall, as Sutton-Kennerly and MPS found it, allowed a staggering 7.48 gallons of water per hour to penetrate the surface.
"We knew it was leaky, but we didn't expect that much," said Mr. Wells. That volume of water soaking into the wall is easily enough to make its way to the interior, causing mold and stains — exactly the problems the Asheville City Building is experiencing.
MPS then repointed the test panel. They used a Type N mortar and followed Secretary of the Interior standards for preservation of registered landmarks. While the pointing mortar used for the test area was made using a commercially available sand, the same originally-specified coarse-grained sand from the nearby French Broad River use was located and will be used for all future pointing on the building.
MPS let the new mortar cure, then reattached the test apparatus for another round.
The repaired wall withstood the simulated storm much better, at only 2.93 gallons per hour — well within an “expected” range for masonry of this type, and an improvement, by the numbers, of 60.9 percent.
“At the suggestion of Jeff Erdly, CEO pf MPS, we decided to take it one step further,” Mr. Wells said. “We wanted to see if we could reduce the water penetration even more by limiting the brick absorption.”
MPS recommended and roller-applied PROSOCO’s masonry water-repellent Sure Klean Weather Seal Siloxane WB Concentrate. The “WB” stands for “water-based,” which, along with “no odor,” was a Sutton-Kennerly specification.
The penetrating treatment soaks into microscopic masonry pores where it chemically bonds, lining the masonry pores with water-repellent molecules. Liquid water won’t enter the pores. However, water that’s already in the masonry can still evaporate out — a characteristic known as “breathability.”
The protective treatment isn’t an alternative to repair — any small gap in the masonry or mortar joints will still admit water — but the normal porosity of masonry is taken out of the game.
A third round of ASTM C1601 confirmed it. Water penetraton decreased again from 2.93 gallons per hour to .76 gallons — a virtually negligible amount of water penetration, and an 89.9 percent improvement over the original unrepaired wall.
“The testing helped us judge the effectiveness of the repointing and water repellent procedures,” Mr. Wells said. “Now that we know how much benefit they bring to the building, our next step will be to include them as we evaluate our recommendations to the building owner.”
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