The city will improve the roof at Riverbend Elementary School, which has leaked since the school opened three years ago, but it won't be a perfect solution, officials warn.
Larger air vents will be added to the roof ridge, and more waterproof membrane will be placed under shingles near the eaves. That should reduce ice damming, which causes backed up water to drip between the shingles. But it won't eliminate the damming because of the winter climate in Juneau, with its freezes and thaws, city architects said.
Ice dams occur because heat builds up in the school's attic. The heat melts the roof's snow, which flows to the eaves, where it freezes because it's colder there. Then more melted snow builds up behind the ice dam, and it can flow between the roof shingles into the school.
"What we're doing out there is not going to solve the school district's problem," said project manager Rod Wilson of the city Engineering Department. "What it's going to do is give them more time to react to the ice dams."
The school's architect, Jensen Yorba Lott, has agreed to buy the ventilation materials and supply the designs, under a recent settlement with the city, which owns Juneau's public school buildings.
JYL President Wayne Jensen said it has been working on the problem periodically over three years. "We haven't been fighting with the city. We've been trying to solve it as well."
The city will buy the waterproof membrane, and will pay the original contractor, Coogan Construction, about $45,000 to install the new vents and the membrane, said city architect Catherine Fritz.
That's what the city would have paid to install the larger vents initially, said City Manager Dave Palmer. The architects have credited the city for the original vents, he said.
"The city agreed to pay for what we would have paid for had it been done right the first time," Palmer said.
About 40 percent of the vents were added as a test last December, Wilson said. The rest of them might be put on before Thanksgiving. The waterproof membrane might be installed after the school year is over so the work noise doesn't disrupt classes, he said.
Last fall, Coogan at its own expense fixed a separate problem with the roof. The contractor replaced nails that attach the shingles to a plywood base. The original nails were too long, and some of them were working their way out, Wilson said.
This winter, also at its own expense, Coogan will trim the points on shingles in the "valleys" between roof slopes. The points were catching water and sending it to the side, where it could eventually drip between shingles and into the school, Wilson said.
Riverbend, which opened in August 1997, has leaked since its first year. Coogan also has replaced the screws that attach the plywood sheets to a metal base.
City architect Fritz attributed the building's original flaws to construction errors by Coogan, foreseeable and unforeseeable design errors by Jensen Yorba Lott, and inadequate oversight by Wilson Engineering, which inspected the work.
"In the end everyone concluded there wasn't one culpable party," Palmer said. The Riverbend roof is similar to one at Dzantik'i Heeni Middle School, which has worked well. But apparently there isn't as much wind at Riverbend to ventilate the roof.
"At the end, everybody kind of stepped up to the plate and picked up a piece of it," Palmer said.
The roof expert cost the city about $6,600 and attorney fees were about $8,000, Wilson said.