When you see a deck quote that's noticeably cheaper than the others, the corner being cut is almost always underground — in the footings. In Minnesota, that's the one place you never want to save money. Here's why.

The Short Version

  • Minnesota's frost line runs 42–48 inches deep
  • Footings must reach below that line to stay put
  • Shallow footings heave — they get pushed up by freezing soil
  • Heaving racks the structure, cracks posts, and bows boards over a few winters

What "frost line" means

The frost line is how deep the ground freezes in winter. In Central Minnesota that's roughly 42–48 inches. Anything above that depth is in soil that freezes and thaws — and freezing soil moves. Anything below it sits in stable, never-frozen ground.

Why shallow footings fail

When water in the soil freezes, it expands, and that expansion has to go somewhere — usually up. A footing that doesn't reach below the frost line gets shoved upward a little each winter. This is called frost heave. One winter you might not notice. After three or four, the deck is racked, the posts are cracking, and the boards are bowing. We get called to fix this constantly — and the fix (re-setting footings) costs far more than doing it right the first time would have.

Why doing it right costs more — and is worth it

Digging a 4-foot footing is real work: real digging, real concrete, real labor that contractors in warmer states simply don't have. That's a big part of why Minnesota decks legitimately cost more than the national averages you find online. When a quote skips it, you're not getting a deal — you're buying a deck with a few good winters in it.

How to spot it in a quote

Ask any contractor directly: how deep are your footings? The right answer is "below the frost line, 42 to 48 inches." If they hedge, or talk about surface blocks or shallow piers for an attached or elevated deck, keep shopping. A reputable builder puts footing depth in writing.

The bottom line

Footings are the part of your deck you'll never see and the part that decides whether it lasts 5 years or 25. In Minnesota, deep is not optional — it's the whole game.

Frequently Asked Questions

Below the frost line — roughly 42–48 inches in Central Minnesota. Footings shallower than that get pushed up by frost heave and rack the structure over a few winters.

When water in the soil freezes it expands and pushes upward. A footing not set below the frost line gets shoved up a little each winter, eventually cracking posts and bowing boards.

Frost footings. Digging 4 feet down and pouring proper concrete footings is real labor that warm-climate builders skip — it's a legitimate reason MN decks cost more than national averages.

Related: Deck Building  •  Concrete Work  •  Deck Cost Guide