Field guide

How to Estimate a Deck Build Without Blending the Systems

Per-square-foot deck folklore collapses the four systems into one number and then wonders where the margin went — the answer is always stairs, railing, and height. Here's the systems method, count by count.

System 1 — Foundation

Footing count from the beam layout (spans per your species/size tables), depth to frost, and access for the auger vs. hand digging. Price per footing; note inspection timing. On sloped or tall decks, footings and posts scale with height — this is the first place height quietly adds cost, so say it in the quote.

System 2 — Frame

Ledger (flashing detail named — it's the code item inspectors check first), joists at the spacing your surface demands (composites often want 12" o.c. on diagonals), beams, hardware, and blocking. Price per square foot at your tracked framing rate, with a height/access multiplier you state rather than swallow.

System 3 — Surface

Area × waste by pattern (8–10% straight, 15%+ diagonal or picture-framed), fastener system named — hidden clips price differently than face screws, in both material and labor. Quote wood and composite as option lines when the customer is deciding; the frame line barely changes, and the honesty sells.

System 4 — Guards and stairs

• Railing: linear feet × your rate per infill type — balusters, cable, glass are different days.
• Stairs: count rises, price per rise. Stairs are framing, cutting, and railing compressed into the smallest, slowest square footage on the job — the classic underestimate.

Then the arithmetic that keeps it

Sum the systems, add demo and disposal if replacing, apply overhead, and divide by (1 − target margin) — verify the divide method on the free margin calculator. Narrated into FieldSquire at the site, the whole method drafts itself at your saved rates — the carpentry estimating app is free for 14 days.