Up on the rooftop: Snow, snow, drip; building owners fret in winter’s icy grip

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Heavy snowfall early in the winter can cause accumulations that put a roof -- especially flat a one – at risk for collapsing.
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Roofing experts say the problem of ice dams doesn’t usually happen until later in the winter but can happen on any roof.

Talk about it

Before melting rains fell and washed many rooftops clean of snow and most ice, St. Croix County issued a building-safety advisory last week warning building owners about the dangers of accumulating snow on rooftops.

It said about two feet of snow had fallen in the area during recent weeks and that some roofs might be in danger of collapsing under heavy snow.

“Rooftops at the highest risk are those with wide unsupported spans, flat rooftops or rooftops with minimal slopes. Emergency Management warns rooftops can be dangerous. Extreme care must be taken in the removal of snow from rooftops. If owners are unsure or unable to remove the snow themselves, a professional may be hired.”

While most of that immediate danger passed with the rains, lessons learned while researching the advisory are worth passing along.

City Building Inspector Joe Lenzen said he’d already been on his roof clearing snow three times this year.

“This is a poster-child year for ice dams,” he declared, adding that lots of snow came early this year and was followed by arctic air.

He’s taken many calls from people concerned about snow and ice accumulation. Lenzen explained that ice dams form when snow on the roof begins to melt. It inevitably gathers and re-freezes, often on the gutter or eave of a home.

Lenzen said it’s very important to make sure the vents on a building’s roof are clear of snow. That includes dryer, sewer, roof, attic, and oven or stove vents.

Lenzen said it isn’t uncommon for snow to pack into the vents and prevent them from functioning properly, which can create temperature variations in the roof.

Other factors affecting roof temperature are the amount and type of insulation plus how it’s installed, as well as attic temperature.

He says the roof deck and sheathing should remain cold so that owners don’t get melting. It’s proper to have cold air between the attic insulation and roof.

“You don’t want that heat from underneath,” said Lenzen.

He agrees even a perfect roof can be susceptible to ice dams, and when water flows, it can create bigger problems by getting underneath shingles and tar paper.

The inspector calls the snow and ice-dam removal process delicate and dangerous. He advises calling a bonded or insured professional to do the job.

Lenzen said many roofing contractors do the work, as well as specialty companies, some landscapers, and other businesses with a bucket truck or similar equipment.

He said do-it-yourselfers beware that “brittle cold” makes everything susceptible to breakage, “You have to be very, very careful that you don’t damage the shingles.”

Contractor confers

Joe Karras of BlackWolf Exteriors in River Falls said last week, “I have never experienced a winter like this. I have gotten a lot of calls.”

He offers snow removal by a crew who is used to working on rooftops and knows how to get around safely up there. Karras said he doesn’t use high-tech equipment such as steamers like some companies do.

“It’s a very specialized thing not typically needed until February or March,” he said.

Karras said only an engineer can tell a person how much of a “stress load” their roof can handle. He recommends using a roof rake in a downward motion -- from top to bottom -- to avoid any breakage. He’d observed the rakes selling out fast.

Karras said most problem areas happen on the north side of a home, in a spot the sun doesn’t touch, and sometimes where a sidewall intersects a roof line.

While he warns against using any kind of sodium chloride (salt) on a roof since it can eat away the fiberglass mat of the shingles, Karras shared a recently learned technique anyone can try.

Fill nylon hosiery with de-icing salt and lay it on the gutter where ice usually forms. It melts the dam slowly and drains into the gutter.

Asked about how much it costs to have a professional remove rooftop snow and ice dams, he said he’d just heard some contractors talking about prices.

For a company with steamers, Karras estimates the cost to be $200-$300 per hour. Manual snow removal costs about $75 per person per hour, but it’s difficult to estimate price until they see the roof.

“A typical removal might be 2-3 hours for two people,” he said.

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