The cheapest way to build a deck

Seven ways to a 12x12 deck, cheapest first

The spread from top to bottom is more than ten to one. The two biggest levers are labour (roughly half a contractor's price) and the board: composite costs about twice as much as pressure-treated pine to buy.

Stay low and skip the railing

A deck under about 30 inches high generally needs no guardrail, and many places exempt a small, low, detached deck from a permit. Height also drives the frame: taller posts, bigger footings, bracing and a longer stair. In the wood deck cost calculator a 12x12 pressure-treated deck is $2,566-$3,279 at ground level and $2,851-$3,643 at standard height, about 10% more, before any railing.

Railing is priced by the foot and adds up quickly: the deck railing calculator puts 40 ft of composite railing at $2,380-$3,360 installed, close to the price of the whole ground-level deck.

Design to standard lumber lengths

• Keep it a rectangle. Angles, curves and levels add cuts, waste and labour; the deck cost calculator adds 20-40% for multi-level or complex shapes.
• Make the depth match a joist length. A 12 ft deep deck uses 12 ft joists with no waste; 13 ft means buying 14s.
• Make the length suit the boards. On a 12 ft or 16 ft run, every board is used whole or cut once.
• Keep joists at 16 inches on centre and board widths standard; the joist spacing guide shows what each spacing costs in extra joists.

Build it yourself, but price the tools honestly

On the same 12x12 pressure-treated deck, the DIY deck cost calculator shows how the tool bill moves the total:

Against a contractor price of $2,851-$3,643, buying every tool for one small deck can wipe out most of the saving. Rent the auger, borrow what you can, and see tools needed to build a deck for what is worth buying.

Where not to save

• Footings: dug to your frost depth and sized for the load. A heaved footing costs far more than the concrete it saved; see deck footing options.
• The ledger: flashed and bolted, never nailed. This is where decks fail; see the deck ledger board guide.
• Hangers and structural screws: a few dollars each, and they hold the joists up.
• Joist tape on a pressure-treated frame you plan to keep for decades.

The hardware for the 12x12 example is listed below, sized from the deck materials calculator for a 2 ft high deck attached with a ledger.

Timing and quotes

Contractors are busiest from spring to early summer. Booking a build for late autumn, or signing in winter for an early spring start, often gets a better price and a faster start. Get at least three quotes for the same written scope, and check each line against the deck quote checker. If you are weighing a patio instead, the deck vs patio guide compares the two.