When the shingles started to slough off her Salt Lake City home, water crept in.

But Maria Kempton, a single mother raising a 12-year-old son, couldn't afford the costly repairs her aging roof needed. And then a "blessing" showed up Monday.

Calling themselves World Changers, about 250 teenagers from across the United States arrived in the Salt Lake Valley Monday morning.

They'll spend the next week painting, roofing, building wheelchair ramps and replacing siding at 28 homes for low-income, elderly and disabled residents around the valley.

"I could not have fixed this," Kempton said, as a group of high school students peeled back layers of old shingles on her west-side home. "Absolutely not. This is thousands of dollars. I can't even imagine. No way. It's just a blessing."

This is the third year World Changers, volunteers made up mostly of Southern Baptist and other evangelical Christians, have partnered with Salt Lake City.

For one week, they'll spend their days at 28 homes painting homes and scraping away layers of old shingles until their faces are covered with dirt and roofing tar and the arms are burned red. They will spend their nights on cots at Granite Park Junior High School.

"It's pretty dirty, but it's not as bad as I thought it would be," said Anna Longstreet, a high schooler from Pasco, Wash., as she took a break for lunch Monday afternoon.

A few ministers and a handful of college students lead the volunteer group. The city provides supplies and supervision to make sure projects meet building codes.

"It's invaluable," said Sara Richardson, with the city's Housing and Neighborhood Development Department. "We're able to help so many homes at a fraction of what it would normally cost. And a lot of these homeowners don't qualify for other programs. This really helps us reach out to our residents and make sure we're keeping our neighborhoods safe and comfortable places."

For many of the volunteers, it's also an opportunity to spread the gospel.

"I believe that God loves us and he wants us to share that love," Longstreet said.

Ethan Townsley, of Kingman, Ariz., wanted to see Italy this summer, but instead ponied up the $270 fee to settle for a rooftop view of Salt Lake City.

"I just felt like God was calling me to this place," he said.

World Changers conducts similar service projects across the country. This summer, Lauren McSwain, a senior at North Carolina State University, has helped organize volunteer efforts in Iowa and Wyoming. After Utah, she's off to Texas.

"We're doing what God called us to do," she said.

Maybe it's not how most teenagers would choose to spend their summer vacation, but it's a worthwhile cause, said Cameron Groteluschen, of Buffalo, Wyo.

"Teenagers get a bad rap these days, and some of them probably are that way," said the 19-year-old. "But for the most part, these are good kids."

e-mail: afalk@desnews.com