How to build a deck, step by step, the way the inspector will check it

The deck this guide builds

A how-to without dimensions can't tell you how many joists to buy, so here is the one on the bench. It runs 16 ft along the back wall and 12 ft into the yard, 192 sq ft. The surface sits 36 in. above grade. A 2x8 ledger bolts to the house band joist. Three 6x6 posts carry a doubled 2x10 beam set 10 ft 6 in. out from the house, and 2x8 joists at 16 in. on center cantilever about 1 ft 1-1/2 in. past it. One 36 in. stair comes down the long side. The guard wraps the three open sides.

Every framing size comes out of DCA 6, the American Wood Council's free prescriptive guide. It is written to match the International Residential Code for single-level decks that stay within its limits, and most building departments accept a plan drawn from it without an engineer. The same deck is priced line by line, with labor and a pressure-treated vs composite payback, in the 12×16 deck cost guide. This page is the build.

Deck materials list with quantities and prices

Counts come from the site's deck math: 26 rows of 5-1/2 in. boards at a 1/8 in. gap lay out at 146.1 in. across the 144 in. frame, and 13 joists at 16 in. cover 16 ft. Prices are Menards shelf prices on September 19, 2026, before tax and rebates.

The hardware line is itemized in the cost guide. Two things on it deserve a second look at the counter. DCA 6 wants connectors hot-dipped to G-185 or stainless in treated lumber, and the holdown I found is G90. The lags are listed as galvanized without saying hot-dipped. Ask for the heavier coating on both. If you live within 300 ft of salt water, DCA 6 calls for 304 or 316 stainless throughout.

Every piece of framing on that list is labeled ground contact, and that is on purpose. The AC2 brochure from the treater lists deck posts, joists and beams as ground-contact uses, because they are hard to replace and critical to the structure. The cheaper above-ground stock is for decking and rails.

Run other sizes through the deck cost calculator. It uses the same board and joist math as this list.

What tools do you need to build a deck?

You need a circular saw, a drill-driver and an impact driver for the lags, a 4 ft level, a framing square, a speed square, a 100 ft tape, string, stakes, line levels and a post-hole digger. A wheelbarrow and a hoe mix 41 bags of concrete fine if two people take turns.

Rent a one-person power auger if the soil is rocky or the frost line is deep; five holes 36 in. deep by hand is a long day. A miter saw is nice for square spindle cuts and not necessary. A hidden-fastener tool only matters if you go composite. I have not priced the tools here because what you already own changes the answer more than any store price.

How to build a deck, step by step

Each step ends with the check that tells you it is right before you move on.

1. 1. Pull the permit and call 811

   Draw the plan from DCA 6 and submit it. The 2021 IRC only exempts a deck of 200 sq ft or less that sits no more than 30 in. above grade, is not attached and does not serve the required exit door. This one is attached and 36 in. up, so it needs a permit. Then call 811 before anyone digs. DCA 6 says it in as many words and forbids footings over septic fields, utility lines or enclosed meters.

   Check: permit card in hand, and the utility marks are painted on the lawn before the first shovel.

2. 2. Lay out and square the deck with 3-4-5

   Snap a line on the house for the top of the ledger, then run string lines for the two sides and the beam. For a 16 × 12 ft rectangle the diagonal is 20 ft, because 12, 16 and 20 are the 3-4-5 triangle times four. Measure both diagonals from corner to corner. Adjust the string until they match.

   Check: both diagonals read 20 ft within 1/4 in. of each other, and the beam line sits 10 ft 6 in. from the house at both ends.

3. 3. Dig and pour footings below the frost line

   DCA 6 wants every footing on undisturbed soil at least 12 in. below grade or below the frost line, whichever is deeper, and it wants the building official to see the holes before concrete goes in. At a 36 in. frost depth, each of the three beam posts gets a 24 in. round pad 10 in. thick, the Table 4 size for a beam span up to 8 ft and a joist span up to 14 ft on 1,500 psf soil, with a 12 in. tube up to 2 in. above grade. The two stair posts get full-depth 12 in. tubes. That is 18.33 cu ft, 41 bags. Set the post bases in the wet concrete, lined up on the string. Any footing closer than 5 ft to the house wall has to bear at the depth of the house footing. For other footing sizes, the concrete calculator turns diameter and depth into bags.

   Check: inspector signs off on the holes; each post base sits on the string line and within 1/8 in. of level.

4. 4. Flash and bolt the ledger

   Pull the siding where the ledger goes. DCA 6 requires the siding off and corrosion-resistant flashing at any ledger on a wood-framed wall, and it rules out aluminum touching copper-treated lumber. Tuck the flashing under the housewrap above, let it lap over the ledger top with a drip edge, and bolt the 2x8x16 ledger to the house band joist with 1/2 in. lag screws. Table 5 sets 15 in. on center for joists spanning 10 ft 1 in. to 12 ft into a 1-1/2 in. band joist: 13 spaces and 14 lags across 16 ft, staggered top and bottom. Drill 1/2 in. through the ledger and 5/16 in. into the band joist, turn the lags in with a wrench or impact driver, and never hammer them. Add the two lateral hold-downs DCA 6 requires within 2 ft of each end, each rated at least 1,500 lb.

   Check: lag tips come out past the inside face of the band joist, the ledger sits no more than 1/2 in. off the sheathing, and water poured above it runs over the flashing, not behind it.

5. 5. Set posts and build the beam

   DCA 6 makes 6x6 the minimum post, and Table 3A lets a two-ply 2x10 of southern pine span 7 ft 1 in. when it carries joists up to 12 ft. Three posts set 1 ft in from each end and one in the middle give two 7 ft spans. Notch the post tops, drop the beam in, and through-bolt each post with two 1/2 in. bolts. Posts here are about 16 in. tall, under the 2 ft height at which DCA 6 requires diagonal bracing on corner posts.

   Check: the beam crowns up, is level end to end, and sits at ledger height minus the joist depth.

6. 6. Hang the joists

   Thirteen 2x8s at 16 in. on center. Table 2 allows a southern pine 2x8 at that spacing to span 11 ft 10 in., and this layout asks for 10 ft 6 in. The overhang past the beam is capped at the lesser of 2 ft and a quarter of the span, so 1 ft 1-1/2 in. is well inside. At the ledger, each joist sits in a hanger at least 60% as deep as the ledger, filled with the nails the hanger maker specifies. At the beam, a tie holds each joist down. Add the rim joist and blocking over the beam.

   Check: every nail hole in every hanger filled, crowns all up, and a straightedge across the joist tops shows no board more than 1/8 in. proud.

7. 7. Lay the decking with the right gap and fasteners

   For lumber, DCA 6 says space boards about 1/8 in. apart and fasten each one to each joist with two 8d threaded nails or two #8 screws. That is 26 rows times 13 joists, 338 crossings and 676 screws. Every board segment has to bear on at least three joists, so stagger the butt joints. Composite follows its own manual; the UltraDeck board uses clips that set a 1/4 in. gap, 351 of them on this deck.

   Check: a 1/8 in. spacer slides between wood boards along the whole run; 26 rows reach the rim with the last board overhanging or ripped, not jammed.

8. 8. Build guards and stairs to code

   A walking surface more than 30 in. above grade needs a guard at least 36 in. high with no opening a 4 in. sphere can pass. Spindles 1-1/2 in. wide at 5 in. on center leave 3-1/2 in. of air, so 444 in. of guard takes 89. Guard posts are 4x4 minimum, and on the rim each one needs a hold-down rated for at least 1,800 lb, which is where the six holdowns on the list go. For the stair, 36 in. of rise at the 7-3/4 in. maximum riser takes five risers of 7.2 in. and four treads at least 10 in. deep. DCA 6 wants 2x12 stringers, at least three when they are cut, a 36 in. minimum width, and a handrail 34 to 38 in. high once there are four or more risers. The stair posts sit on their own footings. Put a light at the top landing, switched from inside. The stair calculator splits any other rise.

   Check: a 4 in. ball does not pass anywhere in the guard; every riser is within 3/8 in. of the others; you can grab the handrail all the way down.

9. 9. Final inspection, then finish

   DCA 6 says a deck is not used until final inspection and approval. After that, a wood deck gets its first coat of stain once the wood is dry enough to take it; the stain maker's label sets that test.

   Check: signed final on the permit card before the grill goes up.

What is the best material for a deck: pressure-treated, cedar or composite?

The structure has no real choice. The posts, beam and joists should be ground-contact treated lumber, as the treater's own brochure says. The choice is the walking surface and the rail, and the numbers split it cleanly.

Read the fine print before paying for years. The Trex warranty prorates from year 11, pays in replacement boards or a refund, and excludes the labor to tear out and reinstall. It also excludes damage from improper gapping. The AC2 warranty requires a claim within 30 days of finding the failure, the receipt, and an end tag from each failed piece. Keep the tags.

On this 12×16, entry composite adds $707.73 of boards and clips to the materials. What buys that back is the stain you skip. The cost guide runs it: if you would pay someone about $1,031 to restain every two years, composite has paid for itself by year 4. If you restain it yourself, the wood deck stays cheaper for about 24 years. That is the whole answer to "best material" for most yards.

Mistakes that cost money to fix

Crew-hour figures use $105.77 billed per crew-hour, derived below. The pattern is plain: everything expensive on that list is cheap to get right the first time and gets found at inspection.

Is it cheaper to build a deck yourself or hire a contractor?

Cheaper in cash, yes: $2,736.36 against about $7,939.91 hired for this deck, though the savings work out to about a carpenter's wage for the hours you put in. Start with what a crew costs. The BLS May 2025 mean wage is $31.55 an hour for carpenters and $25.02 for construction laborers. BLS employer-cost data for construction in June 2026 put total compensation at $51.96 an hour against $36.13 in wages, a factor of 1.4381 for taxes, insurance and benefits. A two-person crew therefore costs ($31.55 + $25.02) × 1.4381 = $81.36 an hour. With a 30% markup for the truck, insurance and profit (my assumption), it bills $105.77.

The difference is $5,203.55. Two beginners working 80 crew-hours put in 160 person-hours, so the job pays you $5,203.55 ÷ 160 = $32.52 an hour. That is about what a carpenter earns. If your own hour is worth more than $32.52, or if a weekend lost to a failed footing inspection costs you more than the savings, hire it out and use this page to check the bid.

Tools change the math. A power auger rental, a second impact driver and a miter saw can eat a few hundred dollars of the savings if you own none of them. And the first-timer hours are a guess; a pair who has framed before will come closer to 40.

How to check a deck contractor's plan

Ask for the drawing the permit was pulled on and hold it against this list. Joists: size, species and spacing, 2x8 at 16 in. for this layout. Beam: two-ply 2x10 on three 6x6 posts. Footings: diameter, thickness and depth to your frost line. Ledger: 1/2 in. lags at the Table 5 spacing, staggered, with flashing and two lateral hold-downs. Guards: post attachment with rated hold-downs. Stairs: stringer count and a handrail. A bid that names none of these is priced on a deck you can't see yet. Run its material count through the deck cost calculator and compare the labor line to the cost guide's hours.