If you are building a deck in Michigan, one number matters more than the railing style, the decking brand, or anything else you will pick out: how deep the footings go. The answer is about 42 inches, below the frost line, and here is why that single detail decides whether your deck is still flat in ten years.
The short answer: 42 inches, below the frost line
Across most of Michigan, including all of Oakland County, the frost line runs to roughly 42 inches. A deck footing has to be poured below that depth so the soil that freezes and expands each winter sits above the bottom of the footing, not under it. Set a footing shallower than the frost line and you are asking it to ride up and down with the ground every season.
Why frost depth decides whether your deck lasts
When water in the soil freezes, it expands and pushes everything above it upward. This is frost heave, and it is the single most common reason decks in Michigan rack, twist, and pull away from the house. A footing that stops short of 42 inches gets gripped by that freezing soil and lifted. One post lifts, another does not, and within a few winters the deck is no longer level: doors stick, boards gap, and the connection to the house starts to strain.
A footing poured below the frost line avoids the problem entirely. The freezing, expanding soil is above the footing's base, so there is nothing under it to lift. The deck stays put.
What the code requires in Oakland County
Attached decks and most freestanding decks in Oakland County require a building permit and a footing inspection, and they are built to the 2015 Michigan Residential Code. That code sets the below-frost footing requirement, along with rules for ledger attachment, post sizing, and railing height. A permitted deck gets its footings inspected before the concrete is poured, which is exactly the stage where shortcuts get caught.
How we pour footings that do not move
On every deck we build, footings go below the 42-inch frost line with proper bearing at the base, code-compliant ledger attachment and flashing where the deck ties to the house, and hardware rated for Michigan winters. It is slower and it costs more than setting shallow blocks on the surface, and it is the entire reason our decks are still level years later.
The part most homeowners never see: drainage
Michigan Outdoor Creations grew out of a drainage company, and that shows up under every deck. We grade and drain the soil around the footings so water moves away from the deck and the foundation instead of pooling, freezing, and working against the build. Footing depth and drainage are the two things you will never see once the deck is finished, and they are the two things that decide how long it lasts.
Thinking about a deck in Walled Lake or anywhere in Oakland County? We build them below frost, drained, and to code, and we will tell you straight what your lot needs.