DCN ARCHIVES

October 29, 2010

BURNABY SCHOOL DISTRICT 41

A single coat of acrylic stucco is being replaced on this Burnaby, B.C. school with an exterior siding system.

Probe helped target stucco repairs at Burnaby, British Columbia school

Covering an area of 26,000 square metres, Burnaby South Secondary is the largest single school building in the province of British Columbia.

In the parlance of the Burnaby School District, the school was “born” a lot later than most of its counterparts — but that’s not necessarily a good thing.

The school opened in 1992 during a period when the B.C. Building Code allowed the application of thin coats of acrylic stucco to building exteriors without allowing for water drainage.

The result: considerable water damage around the perimeter of the school’s building envelope.

“The acrylic stucco they used came from the U.S.,” says Phil Shepherd, director of facilities with the Burnaby School District.

“But even in California, they required two skins of membrane to protect the building envelope. Here it was treated as conventional stucco with no requirement for a rainscreen.”

But conventional stucco was traditionally applied in thick layers that both protected the building from moisture and allowed it to escape the stucco surface through capillary action. Shepherd reckons the school district was fortunate most of its buildings were built during the student boom of the 1950s and 1960s.

“Schools built during the 1950s using a two-and-a-half inch application of stucco fared much better. The treatment on Burnaby South was an acrylic slurry scratch coat about five-eighths of an inch thick and then a colour coat on top. When the moisture got behind and hit the paper on the gyp rock it created the right type of moisture to create conditions that could encourage the growth of mould. Where the moisture had gotten in, it began to erode the steel studs, particularly at the base plates where the moisture pools.”

Burnaby South was the only school in the district to be built entirely using the acrylic coat application. Four other elementary schools, however, used it on building additions and are slated for building envelope repairs as well.

While the school district was well aware of the problem, it had little money available to rectify the situation. Shepherd says he read about a technology used in the hotel business across the U.S. and Canada where building envelopes were constructed using the same type of acrylic stucco application.

“It’s essentially a probe that sits in back of the stucco and reads the humidity, temperature and amount of vapour in the space and radios out a signal when the numbers become critical,” says Shepherd. “We installed 60 probes around the perimeter of the school, particularly on surfaces that regularly experience incidents of driving rain. We would then investigate those spaces that sounded the alarm.”

Shepherd’s team discovered rusty structural steel and gypsum walls inside classrooms that had reached the saturation point and were becoming soft to the touch. Minor incidents of mould were dealt with and spot repairs and patches carried the building through the next three years.

A $7.5-million refurbishing project for Burnaby South was recently approved.

Repairs include replacement of most of the building’s windows and the application of rain screen technology along the building’s perimeter.

General contractor Vanbots removed and disposed of the damaged stucco and replaced it with a CERACLAD rain screen exterior siding system, composed of pre-finished concrete panels on plywood backing.

The project is scheduled for completion later this year.

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