Introduction
The difference between a deck frame that goes up smoothly and one that fights you all weekend usually comes down to a handful of field techniques — the order you lay out in, how you keep posts plumb while concrete cures, and how you protect post bases from the rot that kills decks early. These are the trade tips professionals use on every post-and-footing job, organized in build order so you can follow them start to finish. Pair them with accurate numbers from the Deck Post Calculator and you will spend build day building instead of re-measuring.
Lay Out in the Right Order
Pros never start digging at the first post location. The correct sequence: establish the ledger position on the house (or the house-side beam line for freestanding decks), pull the outer beam line parallel using the 3-4-5 triangle to guarantee square, then mark every post location along both lines before a single hole is dug. A 3-4-5 check — 3 ft one way, 4 ft the other, exactly 5 ft on the diagonal (0.91 m, 1.22 m, 1.52 m) — at each corner keeps the whole frame square, and square at layout means every joist and deck board fits later without trimming.
Mark post centers with stakes, not spray paint alone — paint fades and stakes survive the auger. And always lay out the full grid first because a spacing error compounds: being 2 inches off on the first post becomes 6 inches off by the third, which is how beams end up missing their posts. The estimating guide shows how to transfer your beam layout from plan to ground accurately.
Use Batter Boards, Not Faith
Batter boards — simple horizontal boards staked a few feet outside each corner with strings stretched between them — are the pro’s way to hold layout lines while you dig. Holes destroy ground marks; strings on batter boards survive everything. Set the boards level with each other, stretch mason’s line to mark each beam line, and drop a plumb bob from the string intersections to center every footing hole exactly.
Keep the strings up until every footing is poured and every post base is set. They are your only reference proving the posts landed where the plan said they would, and inspectors notice when they did not. For a sloped site, set batter boards at the high side and use a line level — never eyeball elevation over a 20-foot (6.1 m) run.
Set Posts Plumb and Keep Them There
A post that cures 2 degrees out of plumb is a permanent lean, and beams magnify the error. The technique: set the post in the wet concrete or on its base, brace it in two directions with diagonal 2x4s staked to the ground, then check plumb on two adjacent faces with a 4-foot level — not a torpedo level, which is too short to read a 6×6 accurately. Only then walk away.
Recheck plumb after 30 minutes. Wet concrete settles and posts drift; the second check catches it while correction is still a push rather than a re-pour. On tall posts (over 6 ft / 1.83 m above grade), leave bracing in place until the concrete reaches initial set, typically 24-48 hours depending on mix and temperature. If you are setting multiple posts in a day, work down the beam line in order and string a line across the post tops to verify they share an elevation before the concrete hardens.
Protect Post Bases from Rot
Wood rot at the post base is the number-one killer of deck frames, and it is almost always preventable. The rules: never bury a post directly in soil — use a standoff post base that holds the post at least 1 inch (25 mm) above the concrete so the end grain can dry. Slope the top of each footing or pier slightly away from the post so water sheds instead of pooling. Use pressure-treated lumber rated for ground contact (UC4A or better) for any post within 6 inches of grade.
For extra insurance on high-value decks, brush a copper-based wood preservative on the buried or near-grade portion of the post and wrap the base with a peel-and-stick membrane before setting it — cheap, fast, and it doubles the margin against the moisture that end grain wicks up like a straw. Keep mulch, soil, and irrigation spray away from post bases for the life of the deck. The material guide covers treatment ratings and connector choices that complement these steps.
Pour Footings Like You Mean It
Dig each hole 4-6 inches (10-15 cm) deeper than the required footing depth and fill the bottom with compacted gravel — this gives water a place to drain instead of sitting under your concrete, and it forgives a slightly uneven hole bottom. Bell out the bottom of the hole wider than the top where soil allows; the wider base resists frost heave and spreads the load. Pour in one continuous session per footing — cold joints between partial pours are weak planes.
Work the concrete with a rod or shovel to release trapped air pockets, especially around the post base anchor bolt you set while the concrete is wet. Crown the top of the footing slightly and slope it away from the post. And respect cure times: keep footings moist and undisturbed for at least 3 days before loading them with posts and beams, longer in cold weather.
Cut Posts In Place, Not on the Sawhorses
Here is the tip that saves more decks than any other: set your posts long, install the beams temporarily or string your beam elevation line, then mark and cut every post top at its true installed height. Grade is never as level as the plan assumes, and pre-cutting posts to a calculated length guarantees a wavy beam line. The formula guide explains why buying long and trimming is built into the estimating math.
Cut with a circular saw from two or four sides on 6×6 stock (no standard blade cuts through 5.5 inches in one pass), seal every cut end with preservative, and set your beam or cap immediately so the fresh cut is never exposed to weather longer than necessary.
Related Guides
- Deck Post Complete Guide — the flagship overview: inputs, formulas, and a worked example in both unit systems.
- Deck Post Common Mistakes — the errors these tips exist to prevent, with fixes for each.
- Deck Post Estimating Guide — accurate layout starts with accurate counts.
- Deck Post Build Checklist — a pre-build and build-day checklist that sequences these tips into a work plan.
- Deck Post Material Guide — treatment ratings, connectors, and concrete types worth specifying.
Get Your Number
Good technique cannot rescue bad numbers — a perfectly plumb post in the wrong location is still wrong. Finalize your layout with the Deck Post Calculator before you pick up the auger: confirm post counts, spacing, footing sizes, and post lengths, then work the tips above in order on build day. Measure twice, dig once, brace everything, and your frame will be square, plumb, and dry for decades.
Disclaimer: Results are planning estimates only. Verify quantities and prices with your supplier and consult a licensed professional or your local building authority for structural or code-related decisions.
