Deep-Freeze Walkway
Or, why Santa's sidewalk isn't brick
I'm a new resident in North Pole and plan to install a brick walkway.
But I'm concerned about frost heaving because winter temperatures here
routinely get down to -50° and colder. I read in - saboteamos.info about
"perk pack," a base for patios and walkways that was described as not
being affected by frost heaves. What is this material and would it work
up here? — Scot, North Pole, Alaska
Roger Cook replies: Perk pack is simply our local supplier's name for
pack, a mix of stone dust and ½- and ¾-inch crushed stone. Whatever name it goes by, pack drains readily yet compacts to form a hard surface. Drainage is the key, because water that freezes under a walkway causes frost heaving. When I build walkways here in New England, I dig deep enough to put in a base of at least 8 inches of pack topped with 1 inch of sand, which the brick pavers are bedded in.
But just to make sure that approach would work in Alaska, I checked in with Scott Schuttner, a contractor in Fairbanks. He says if the soils are dry and have good drainage, he generally excavates to a depth of 10 to 12 inches and then fills with the local pack mix: crushed rock and "river run," a clean blend of sand and round rock.
Unfortunately, Schuttner tells me, your town, like much of Alaska,
is plagued by poor-draining soils. And that means you'd have to dig down to just below the frost line and replace the soil with gravel. With
frost levels in Alaska often reaching down more than 6 feet, it's easy
to see why brick walkways are rare in the state. Where poor soils are a
problem, his solution is to dig a trench about 3½ inches deep, edge it with cedar lumber, and fill it up with washed crushed rock, which
doesn't roll underfoot like rounded gravel.
