Some version of this sad-but-true story happens all the time. It’s happening somewhere, no doubt, right now.
This one began in Seattle, in a 4-year-old, six-story, two-building apartment complex – about 70 units in each building, in 2007. A few residents reported tell-tale signs of water ingress around the windows.
Stains appeared on the interior walls. Paint peeled. Wood liners around the windows decayed.
The owner of the complex – a developer who owns about 30 similar buildings throughout the city – called Tatley-Grund, Seattle, a company specializing in investigation and repair of buildings with water-intrusion problems.
“We initially identified four or five places water was getting in,” said Stacey Grund, a principal and founder of the firm in 1991. “We performed both non-destructive and destructive tests to find the sources of the leaks.”
As testing progressed, the investigators found many more problem areas.
One interesting test involved hanging a calibrated rack of nozzles on the building, to shoot water at the windows. Inside, a pressure chamber with blower and digital manometer was mounted over the window to create a lower pressure than outside, and measure at what pressure window-failure occurred.
This test meets the requirements of ASTM E 1105 and AAMA 502 to simulate wind driven rain. Other investigative procedures included stripping off stucco cladding and interior drywall to expose the water’s path.
They found the vinyl windows were the culprits.
To make a 6-foot-tall by 4-foot-wide window, the manufacturer took two perfectly sound 3-foot-tall by 4-foot-wide windows and molded them together, one on top of the other.
A tiny gap in the molding of the H-bar that connected the two windows let in water. Once in, it ran horizontally down the H-bar. Absence of end dams let the water drain in to the rough opening, where it did its destructive work in the building’s walls.
Tatley-Grund tested five windows on the building, using the spray rack apparatus. All five failed, in precisely the same way.
The implication was clear. With about 275 windows, all with the same defect, the building was a ticking time bomb of mold and decay. Unchecked and given time, the water ingress could eventually make the building uninhabitable.
The developer filed suit against the window manufacturer.
The manufacturer brought in his own consultant. The consultant concurred with Tatley-Grund’s findings, calling them “indisputable.”
The manufacturer had no choice but to accept full liability – a repair tab that rolled in at $3.2 million.
That was the price to strip away the cladding, pull out all 275 or so windows, replace the faulty H-bar with a stainless steel version, and re-set the repaired windows in rough openings sealed with a waterproof, yet breathable fluid-applied flashing.
Then reclad the wall.
The modified windows were proven not to leak, but if they did, the flashing would ensure water drained to the exterior and stayed out of the walls.
“We knew for a fact the windows would work that way,” Stacey said, “because we tested them.”
Using the exact products and procedures they planned to use in repairs, Tatley-Grund built a full-size mock-up window assembly and tested it in a large design verification test chamber.
The chamber is similar to the calibrated spray rack used to test windows already in buildings, except that the spray nozzles are inside the chamber. The exterior side of the window assembly being tested is also inside the chamber, facing the nozzles. The living-space side of the window assembly makes up one outside section of the test chamber.
The air-tight chamber can be pressurized to simulate wind conditions from a mild Spring day to a Category 5 Hurricane. With the pressure cranked up and the water at full blast, the chamber creates a virtual “hurricane in a box” to test both air-tight and water-tight integrity of any window or wall assembly.
Had that kind of design verification testing been done before construction started, Stacey said, this sad story would never have happened.
The leaky windows could have been detected and replaced before the first window was ever installed.
That’s why the story is sad; because the damage was so easily preventable, he said.
Meantime, the developer’s attorney contacted Tatley-Grund about another case he was working on. A newer property owned by another client had the same windows, and showed similar problems.
The good news was that because it was newer, the leaks and damage weren’t as far advanced. In this case Tatley-Grund simply removed the defective H-bars, replacing them with the same leak-proof stainless steel connector they’d used on the previous project.
That repair bill ended up being a relatively economical $700,000, since no strip and reclad was involved, Stacey said.
Other costly design failures Tatley-Grund sees include water penetration through mis-lapped building papers and discontinuous or improper sealants in interfaces between building components such as decks and walls, or wall penetrations from lights or sliding glass doors.
They are failures that cause major, expensive headaches. They are all problems easily catchable and preventable by design verification testing.
Despite the example of the defective window, this isn’t a knock on manufacturers, Stacey said. Some very good products go into making buildings.
But those products don’t always work well with each other, especially under stressful conditions like high-wind and heavy rain.
And there is no way to laboratory- or factory-test each product with every other product it could possibly come in contact with.
That testing has to be done on a project-by-project basis. And the testing must approximate the conditions the project will face over the course of its life.
“I sometimes use the analogy of the building envelope being like a sandwich,” Stacey said.
There are some tasty ingredients out there that make for great sandwiches. But just like construction materials, they don’t always play well together.
If your cutting-edge sandwich design specifies adhering the tomatoes to the salami with peanut butter, topping it with caramelized onions and sandwiching it all between double-layered buttered rye-crisps, you might want to test it first before serving it at your next dinner party.
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