{"id":637437,"date":"2024-10-07T11:22:26","date_gmt":"2024-10-07T15:22:26","guid":{"rendered":"https:\/\/www.familyhandyman.com\/?p=637437"},"modified":"2024-10-09T02:58:56","modified_gmt":"2024-10-09T06:58:56","slug":"frost-proof-concrete-footings","status":"publish","type":"post","link":"https:\/\/www.familyhandyman.com\/article\/frost-proof-concrete-footings\/","title":{"rendered":"Here’s the Key to Frost-Proof Deck Footings"},"content":{"rendered":"The fact that water expands when it turns to ice makes life possible on our planet. However, it also creates headaches for homeowners in the form of busted plumbing pipes, ice dams and damaged gutters. It can even cause deck footings to heave, resulting in leaning deck posts and unstable decks.\r\n\r\nThe climate along California's Central Coast, where I live, is mild enough for builders to ignore this issue. But that's not the case in more northern regions. Ruben Saltzman, CEO of home inspection service Structure Tech, has identified frost heave as one of the most common problems with decks where he works in Minnesota.\r\n\r\n\"Sandy, well-drained soils aren't particularly susceptible to frost heave,\" says Saltzman. \"But soils with higher clay content are.\"\r\n\r\nYou only need a few basic concrete skills<\/a> to pour deck footings, but you do have to ask a few important questions\u2014 the depth of the frost line<\/a> chief among them. In Minnesota, the frost may go as deep as 42 to 60 inches, but a warmer state like Missouri may have a frost depth of only 12 inches. In most of California, it's five inches, which is considered insignificant. Any footing you pour will be deeper than that.\r\n\r\nBecause the frost line varies with region, it is important to check with your local building department to ensure your deck footings are deep enough to withstand the winter freeze.\r\n

What Causes Frost Heave?<\/h2>\r\n\"Solid\r\n\r\nThe fact that water expands when it freezes is the underlying cause of frost heave. When water freezes, it expands about 9 percent\u2014think of how ice cubes are domed above the original water level in an ice cube tray. Ice exerts a pressure of about 50,000 lbs. per square inch when it freezes, which is enough force to lift even a large building. A puny little deck on inadequate footings doesn't stand a chance.\r\n\r\nWater doesn't freeze uniformly in the soil. Instead, it creates thin layers of frost called ice lenses, and when these form under a footing or latch onto the sides of wood or concrete, they actually push the footing upward. That leaves a space under the footing that can get filled in by the surrounding soil, which prevents the footing from returning to its original depth when the soil warms. This is less likely to occur in sandy, well-draining soil than in soil with a high clay content because sandy soil gives water a chance to drain off before it freezes.\r\n

How to Prevent Frost Heave<\/h2>\r\nAs Saltzman points out, there are three ways to prevent frost heave:\r\n

Dig the base of the footing below the frost line<\/h3>\r\nThe bottom of the footing should be several inches below the frost line, so if you're setting posts in a cold place like Minnesota, you'll need to dig to a depth of four to six feet, depending on the region.\r\n

Flare the bottoms of the footings<\/h3>\r\nIf you create a bell shape at the bottom, it will push against the soil above it to resist heaving. However, Saltzman cautions that ice latching onto a concrete footing and exerting upward pressure above the bell can actually fracture the footing, so for deep footings in clay-rich soil prone to freezing, he advises reinforcing concrete footings with re-bar.\r\n

Make the edges of the footing smooth<\/h3>\r\nYou can bury wooden posts, but since there's no way to give wood a smooth surface that will resist ice lenses and won't degrade underground, you're better off sticking to concrete footings<\/a> in cold climates, especially in dense soil. The conventional way to make the edges of concrete smooth is to pour it into waxed cardboard tubes known as sonotubes.\r\n