A deck is judged by its boards and railing, but it lives or dies by the parts underground. Footings, frost depth, soil, and the connection back to the house are what keep a deck level, solid, and safe for decades — or let it heave, sag, and pull away. In Kansas City, where the ground freezes in winter and the clay swells and shrinks with the seasons, this hidden work matters more than the surface you walk on.
Reputable deck builders work to a real standard. The American Wood Council's DCA-6, the residential deck construction guide adopted across the country, defines how footings, posts, beams, joists, and ledger connections should be built. This guide explains those fundamentals in plain terms so you know what a properly built KC deck requires.
When soil freezes it expands, and anything resting above the frost line can be pushed upward with it — frost heave. Over repeated Kansas City winters, a footing set too shallow lifts and settles until the deck is racked out of level and its connections are stressed. The fix is simple in principle and essential in practice: footings reach below the frost line into ground that stays unfrozen, so the deck does not ride the seasons up and down. The exact required depth is set by your local building code and verified at inspection, and it differs between Missouri and Kansas jurisdictions in the metro — we build to your address's requirement.
Much of the Kansas City metro sits on expansive clay — soil that swells when wet and shrinks when dry. That seasonal movement is constant, and it is the reason a deck footing here has to do more than just hold weight; it has to stay put while the ground around it moves.
We address it by digging footings down to stable soil below the frost line and sizing them for the load and the soil, so the posts are anchored in ground that does not heave with every wet-dry, freeze-thaw cycle. Shallow or undersized footings are the root cause of the sagging, out-of-level decks we are often called to replace.
If a deck is attached to the house, the ledger board is the single most important — and most commonly botched — connection. It carries a large share of the deck's load and ties it to the home's framing. Deck failures that make the news are very often ledger failures.
Done right, the ledger is fastened to solid house framing with the correct structural hardware (not nails), and it is flashed so water cannot run behind it and rot the band joist it bolts to. NADRA, the deck builders' association, emphasizes that ledger attachment and flashing are central to deck safety — which is exactly why we detail it carefully and have it inspected.
The detail to insist on
Ask any deck builder how the ledger is fastened and flashed. Structural hardware into solid framing, plus flashing that keeps water out of the band joist, is non-negotiable — it is the connection most responsible for a deck staying attached to the house.
Above the footings, every structural member is sized and spaced for the deck's span and load per the DCA-6 tables. Together they are what make a deck feel solid rather than bouncy underfoot.
Footings
Concrete footings dug below the frost line and sized for the load and soil. On KC clay, depth and diameter both matter so the deck stays level through the seasons.
Posts
Pressure-treated posts anchored to the footings with proper post bases that keep the wood off the concrete and resist uplift, spaced per the DCA-6 span tables.
Beams and joists
Beams and joists are sized and spaced for the deck's span and load. Getting the spans right is what keeps the deck from bouncing or sagging underfoot.
Ledger and flashing
For attached decks, a structurally fastened, fully flashed ledger ties the deck to the house without letting water rot the connection. For freestanding decks, an extra beam and posts replace the ledger entirely.