Every post on your deck funnels its load down to a footing. Get the footing wrong and the whole structure can settle, tilt, or heave — no matter how well the framing above is built.
Why frost depth matters
When water in the soil freezes, it expands and pushes upward. If a footing sits above the local frost line, that seasonal movement can lift and drop your deck year after year. That is why codes require footings to bear below the frost depth, which varies widely by region.
Sizing the footing
Footing diameter depends on two things: the load coming down the post, and the bearing capacity of the soil beneath it. Soft or clay soils need a wider footing to spread the load; dense gravel can carry more on a smaller pad.
Our load calculations account for tributary area, soil bearing, and local frost requirements so your footings are neither dangerously small nor needlessly expensive. Learn more about our load calculations.