Park City Chief Building Official Dave Thacker says it’s been an interesting year for snow load, and big winter storms have put Park City structures to the test.
In a perfect world, Thacker says snow would fall evenly on a roof, but wind causes it to shift, unequally distributing pressure. And with all the snow this year, Thacker says the trouble comes when it melts during the day, becoming heavier, and then freezes again at night. Thacker says sometimes the bottom layer of ice will connect to the roofing material—and what the building department has noted with roofs that have collapsed this season is that base layer of ice will start to shift.
“As that slips, it creates what you can see on the edge of a lot of roofs is kind of a cornice, and so you'll see a lot of ice and snow that's just slid down the roof and is overhanging the home," Thacker said. "It looks dangerous to be underneath, and it really is because it could fall at any time. But what that does to the roof is it puts a different load on the edge of that roof, which then can compromise either a beam or a post because it's not a direct downforce—it's more of a force from the side—because of the way that it's hanging. Then, sometimes posts or beams can be compromised, and roofs can fail.”
A few incidents have been reported to the building department this winter. There’s the Thaynes Canyon home, where a portion of the roof collapsed. Thacker says that situation is directly related to snow loading and not any architectural issues. There have also been a couple of historic structures—a building in the Silver King Mine complex and one on Woodside that caved in—and a porch collapse on Empire. No one was injured in any of the incidents.
Thacker recommends that homeowners walk around and take note of the snow on their houses, and then hire someone to remove the snow. But for the city’s part, the building department doesn’t have the capacity to analyze every structure’s snow load. There are new homes being built up to current code and old homes that were built to past codes that have continued to hold up to the pressure. The only thing the building department can do, Thacker says, is to address snow load as people upgrade or renovate their homes.
“We are able to do a review for code compliance, and then we're able to require specific things to be either upgraded or adjusted, to make sure that they make current standards," Thacker said. "So, as people do pull permits, we're able to do our jobs a little bit differently at that point.”
Thacker says Park City’s standards have changed as they’ve learned more, and actually, the state legislature passed a bill this year to adjust snow load code. Thacker says, though, that Park City’s current snow load criteria—300 pounds per square foot—is stronger, so it won’t be changed.
“It's working," Thacker said. "It may be a little bit extreme for some, or seem extreme, but the reality is it's made for years like this. It's made for years when we are going to have a lot of snow accumulation, to ensure that we can have structures that are able to withstand that type of weather.”
Thacker advises homeowners to be aware not only of their own roofs, but also of their neighbors’ homes, especially in Old Town where houses are close together. Falling ice or collapsing roofs could damage homes nearby.
