Latest News

You hate rough, windshield-cracking chipseal. So why does Ada County keep using it?

Ada County Highway Department workers on a chip-spreader vehicle distribute gravel over a polymer-infused oil while performing chipseal work on South 12th Street in Boise in 2015. Several rubber-tire roller vehicles follow the chip spreader and push the gravel into the oil.
Ada County Highway Department workers on a chip-spreader vehicle distribute gravel over a polymer-infused oil while performing chipseal work on South 12th Street in Boise in 2015. Several rubber-tire roller vehicles follow the chip spreader and push the gravel into the oil.

At least half of The Windshield Guy’s business is from chipseal damage these days, technician Rob Anderson says.

“A lot of the same story,” Anderson said Friday. “Just driving down any one of these streets here in the valley that have been chipsealed, and a rock gets kicked up and cracks a windshield.”

The Ada County Highway District is in the middle of this year’s chipseal season. The district divides the county into six zones, and crews chipseal one zone per year in a six-year rotation.

This year’s chipseal zone occupies most of the Boise Bench,as well as Southwest Boise and part of Garden City. Its boundaries are Orchard Street, Victory Road, Five Mile Road and the Boise River.

A lot of people don’t like chipseal. Besides leading to windshield damage, installing it causes traffic delays. It leaves a rougher surface than asphalt. That’s especially annoying to bicyclists.

But chipseal is cheap and durable. Most roads need a new layer only every other chipseal cycle, or 12 years, district spokeswoman Nicole DuBois said. A new asphalt surface costs about six times as much and might last less than half as long.

This year’s work is scheduled to wrap up in early September,weather permitting.

Anderson doesn’t expect business at The Windshield Guy, at 5373Emerald St., in Boise, to slow down until after the work is done.

“A lot of people would say, ‘I want to get through the chipseal season, and then replace (the windshield),’” he said.

If a windshield doesn’t have to be replaced, Anderson said,The Windshield Guy can fill chips and cracks up to the length of a dollar bill— about six inches. The store injects a resin into the chip or crack to hold the glass together.

Some insurance companies cover windshield damage, Anderson said. They prefer to pay for the resin treatment — $50 for the first application and $10 for subsequent treatments — than to pay $200 or more to replace a windshield, he said.

The district also covers some chipseal damage, paying out $1,000 to $2,000 per year on average, DuBois said.

The chipseal process

Step 1: Preparation. This process starts in the fall, when highway district crews sweep roads and seal their cracks. Trees that will get in the way of chipsealing equipment are trimmed.

Step 2: LMCRS-2H. That’s the industry name for an oil product infused with polymers to make it extra sticky. A truck shoots the oil on each lane as the chipsealing process gets going for real.

Step 3: Put the “chip” in chipseal. A truck loaded with one-quarter or three-eighths-inch rock particles follows immediately behind the oil truck, spreading an even layer on the oil.

Step 4: Roll it in. Rubber-tire trucks, each one with nine tires in staggered alignments, drive over the rocks to set them in the layer of oil. The polymers in the oil help bind the rock to the oil.

Step 5: Cleanup. Trucks sweep up excess gravel.

Step 6: Fogging. After allowing five to 10 days for the chip-oil bonds to set up, a truck removes the excess rocks from the roadway.After that, a truck applies a thin layer of oil - similar in composition to the bottom layer - on top of the chip layer. This step, known as“fogsealing,” helps seal everything in place.

Step 7: Stripes. A few days after the fogseal is applied,crews paint lane stripes on the new, very black road.

Chipseal 101

What is it?

Chipseal is a hardy, rock- and polymer-infused coating for asphalt or other road surfaces.

Why chipseal?

It’s cheap and durable. Asphalt is smooth, but it wears more quickly. It also costs more than 6 times as much as chipseal. Within a couple of years of laying an asphalt road, Ada County Highway District tries to put a chipseal coat on top of it to preserve its integrity. A chipseal coat lasts anywhere between six and 12 years, depending on traffic, weather and other factors.

How long will this last?

The highway district started this year’s chipsealing process in June and expects to complete it by the early September.

How much does it cost?

About 20 cents per square foot, compared to about $1.27 per square foot for an asphalt overlay, DuBois said.

How many layers of chipseal will a road take?

There’s not a prescribed number, district spokeswoman Nicole DuBois said.

“Over time, multiple chip seal layers can create a bit of a lip,” she said. “But generally, a roadway will show other signs of wear that a chip seal could not repair that would qualify it for an(asphalt) overlay.”

What about my cracked windshield?

This is a common problem. People driving over a fresh chipseal also can kick up chips into their own bumpers, brakes and other car’s windshields. People sometimes complain about this happening even when they’re driving at the suggested 20 mph speed limit. If you have a complaint about damage, send an email to or call 208-387-6100. The district will forward your complaint to a third party to investigate it.

People also complain when the dips from manhole covers get deeper because the chipseal layers raise the height of the surrounding road. Ada County Highway District tries to minimize manhole dips, DuBois said. But the district likes to avoid adjusting the height of a manhole, which can cost thousands of dollars.

Stones and your windshield

Automobile windshields are made up of laminated safety glass, a sandwich of two pieces of glass fused to a central rubber layer. The central layer serves as a shock absorber to reduce impacts and lower the change of breaking. If the glass does shatter, the rubber layer holds the pieces in place.

A repairable rock chip will shatter the top layer but usually won’t penetrate to the rubber. An epoxy can be applied under vacuum to fill the void and apply force into the center of the chip to keep the cracks from spreading.

Long cracks are troublesome, because the repairing force the epoxy provides isn’t in the right direction to keep the cracks from spreading. It’s also more difficult to get the epoxy into a crack than into a chip.

If the damage ruptures that rubber layer or breaks the inner layer of glass, repair is generally not possible.

Statesman science-reporting intern Kevin Davenport contributed “Stones and your windshield.” Sven Berg: 208-377-6275, @SvenBerg51