How Much Does It Cost to Build a Deck?

A built deck typically runs $25 to $60 per square foot installed in the US, which puts a common 12 × 16 ft deck somewhere between roughly $5,000 and $11,500. Homeowners almost always shop the decking boards first, but the boards are usually the second- or third-largest line on the invoice. The frame under them, the railing around them, and the stairs off them are where the money actually goes.

What a Deck Costs, by Size and Material

Decks are priced per square foot of deck surface. The ranges below are for a straightforward rectangular deck, roughly 2 to 4 feet off the ground, with railing on three sides and one short flight of stairs. Ground-hugging decks come in lower; anything elevated a full storey comes in much higher.

Note how little separates the material choices at the small end and how much separates them at the large end. On an 80 sq ft deck the jump from treated lumber to PVC is a couple of thousand dollars; on a 480 sq ft deck it is the price of a car. If budget is tight, the decision that matters most is how big, not what surface.

Where the Money Actually Goes

On a typical mid-size deck the invoice splits roughly like this. Percentages shift with material choice, but the shape holds:

Two things surprise people here. First, railing is frequently the most expensive component per unit — a composite or aluminium rail system at $60 to $150 per linear foot means 40 feet of railing can cost more than 200 square feet of decking. Second, stairs are priced per step for good reason: each one needs stringers cut, treads fit, and a code-compliant handrail, and a landing at the bottom often needs its own concrete pad.

What Drives the Price Up

1. Height off the ground

This is the single biggest multiplier. A deck 18 inches off grade needs short posts and no guardrail in most jurisdictions. Push past roughly 30 inches and code requires a guardrail; push to a second-storey deck and you add long posts, larger footings, lateral bracing, more stairs, and scaffolding or fall protection for the crew. A second-storey deck commonly costs 40% to 80% more per square foot than the same deck at grade.

2. Shape

Rectangles are cheap. Every angle, curve, bump-out, wrap-around and inset costs framing time and generates offcut waste. A 45-degree corner or a picture-frame border can add 10% to 20% in labour and waste on an otherwise identical deck. Diagonal decking adds material waste of roughly 15% versus about 5% for a straight run.

3. Footings and frost depth

Footing depth is set by your local frost line, not by preference — it ranges from a surface pad in warm climates to 48 inches or more across the northern US. Deeper footings mean more digging, more concrete, and sometimes a machine on site. Rocky ground, high water table, or a required helical pile system on poor soil can each add substantially. Check your local requirement before budgeting this line.

4. Site access

If a truck and a mini-excavator can reach the build area, everything is faster. If lumber has to be carried through a house or over a fence, and spoil has to be barrowed out the same way, labour hours climb sharply for work that produces nothing visible.

5. Ledger attachment vs freestanding

Attaching to the house is usually cheaper, but it requires removing siding, installing proper flashing, and lag bolting or through-bolting into the rim joist. If the existing rim joist is compromised, or the house has stucco or brick veneer, a freestanding deck with its own beam line is sometimes the cheaper and safer answer. This is a decision to make on site, not on paper.

Decking Materials Compared

The board itself is a long-term cost decision more than a purchase decision. Material prices below are decking boards only, not installed:

The honest comparison is total cost of ownership over 25 years. Treated pine is cheapest to buy and needs to be cleaned and resealed roughly every other year — call that a weekend and $100 to $250 in product each time, plus a likely board replacement or full rebuild within 15 years. Capped composite costs two to three times as much up front and asks for a wash. If you plan to be in the house more than about 12 years, composite usually wins on lifetime cost. If you are selling within five, treated lumber is the rational choice.

DIY vs Hiring Out

Decks are one of the better DIY structural projects, because unlike a concrete pour there is no clock. You can frame on Saturday, stop, and continue in three weeks. Materials typically account for 45% to 60% of an installed price, so a competent DIY build genuinely saves real money.

• What makes it feasible: the work is repetitive, mistakes are usually unscrewable, and the tool list is short — circular saw, drill, level, string line, and a way to dig footings.
• What catches people out: laying out square, getting footings at the right depth and spacing, sizing beams and joists for the span, and flashing the ledger correctly. Ledger flashing is the most common cause of serious deck problems and it is invisible once the decking is on.
• What still needs a professional: anything more than one storey up, anything where the ledger attaches to a wall you cannot inspect, and any deck the inspector needs to see before you cover it.
• Permits still apply to DIY. Most jurisdictions require a permit for a deck over 30 inches high or over 200 square feet, and an unpermitted deck reliably surfaces during a home sale.

A sensible middle path is to hire out the footings and frame and do the decking, railing and finish yourself. The structural half is where code compliance and span tables matter; the surface half is repetitive work you can do at your own pace.

How to Compare Deck Quotes

Get three, and force them onto the same scope. Ask each builder to write down:

1. Joist size and spacing — 2×8 at 16 in. on centre is not the same deck as 2×10 at 12 in. on centre, and composite decking often requires 12 in. spacing.
2. Beam size and post spacing, and the span they are designing to.
3. Footing type, diameter and depth, and whether that depth meets local frost requirements.
4. Decking product by brand and line — "composite" spans a $4 board and a $13 board.
5. Fastener system — hidden clips, face screws, or a mix, and whether the framing hardware is rated for contact with treated lumber.
6. Railing system and linear footage, priced separately.
7. Stair count, tread width and handrail, plus whether a landing pad is included.
8. Ledger detail — flashing type, fastener schedule, and whether siding removal is in scope.
9. Whether permit fees and inspections are included, or billed to you later.
10. Warranty — separate the manufacturer board warranty from the builder workmanship warranty. They are not the same and only one of them answers the phone.

Where You Can Save and Where You Should Not

Real savings

• Build a smaller rectangle. Every dollar scales with area, and most decks are furnished for a table and four chairs regardless of size. Dropping 16 × 20 to 14 × 18 cuts roughly 20% off everything.
• Skip the railing where code allows. Under about 30 inches of drop, most jurisdictions do not require a guardrail, and railing is the priciest component per foot. Confirm your local threshold.
• Use treated lumber for the frame and spend the difference on the surface. That is what professionals do anyway.
• Do the decking and railing installation yourself after a pro does the structure.
• Build in the shoulder season. Deck crews are booked solid in late spring; autumn quotes are often better.
• Face-screw instead of hidden fasteners. Hidden clip systems add roughly $1 to $2 per square foot in product and meaningful labour time. It is purely cosmetic.

False economies

• Widening joist spacing to save lumber. Going from 12 to 16 in. on centre under composite decking causes visible sag between joists and voids most board warranties.
• Undersizing joists or beams for the span. A deck that bounces when you walk on it is a deck that was framed to the wrong span table, and it cannot be fixed from above.
• Shallow footings. Footings above the local frost line will heave, and a heaved deck racks the frame, the ledger and the stairs together. This is the single most expensive mistake to correct.
• Skipping ledger flashing. Water tracking behind an unflashed ledger rots the house rim joist, not just the deck. Deck collapses overwhelmingly begin at the ledger.
• Using non-rated fasteners and hangers with treated lumber. Modern treatment chemistry corrodes ordinary galvanised hardware. Hot-dip galvanised or stainless is a small premium on a small line.
• Skipping joist tape. Roughly $50 to $150 of self-adhesive tape over joist tops keeps water out of the screw holes and adds years to the frame. It is one of the best value items on the whole build.
• Building without a permit. It saves a few hundred dollars now and reliably costs more at sale, at refinance, or at an insurance claim.

The pattern is the same one you see on every structural project: saving on work you can supply yourself and on size and cosmetics is sensible. Saving on the structure under the surface is not, because it is the part you cannot inspect later and the part that fails expensively.

Frequently Asked Questions

How much does a 12x16 deck cost?

A 12 × 16 ft deck is 192 square feet. In pressure-treated lumber expect roughly $3,800 to $7,700 installed, in capped composite roughly $6,200 to $11,800. Elevation, railing length and stair count move that range more than the decking choice does.

Is composite decking worth the extra cost?

It depends on how long you are staying. Capped composite costs two to three times as much up front but needs only washing, while treated lumber wants cleaning and resealing every two to three years. Past roughly 12 years of ownership composite usually wins on lifetime cost; under about five years it does not.

What percentage of a deck cost is labour?

Typically 40% to 55% of the installed price. That share rises with height, complexity and poor site access, and falls on a simple ground-level rectangle. It is also the share you can recover by doing part of the work yourself.

Why is deck railing so expensive?

Because it is priced per linear foot and manufactured systems are engineered to resist a code-mandated load. Composite and aluminium rail systems commonly run $60 to $150 per linear foot installed, so 40 feet of railing can cost more than 200 square feet of decking. Site-built wood railing is cheaper but takes more labour hours.

Do I need a permit to build a deck?

Usually yes. Most US jurisdictions require a permit for a deck over about 30 inches above grade or over roughly 200 square feet, and any deck attached to the house. Thresholds and footing depths are set locally, so confirm with your building department before ordering materials. An unpermitted deck reliably surfaces during a home sale.

How much does a second-storey deck cost?

Commonly 40% to 80% more per square foot than the same deck at grade. The extra goes into longer posts, larger footings, lateral bracing, a much longer stair run, and fall protection or scaffolding for the crew. It is also the case where hiring a professional is least negotiable.

How much do deck stairs cost?

Roughly $150 to $400 per step installed, because each step needs stringers cut, treads fitted, and a code-compliant handrail. A landing pad at the bottom is often a separate concrete cost. A long flight from an elevated deck can easily be a four-figure line on its own.

Can I build a deck myself and save money?

Yes, more realistically than with most structural projects, because there is no time pressure and mistakes are usually reversible. Materials are typically 45% to 60% of an installed price. The parts to be careful about are square layout, footing depth, span sizing and ledger flashing — the last of these is the most common cause of serious deck failures.

How deep do deck footings need to be?

Below your local frost line, which ranges from a surface pad in warm climates to 48 inches or more in the northern US. This is set by local code and soil, not by preference. Footings above the frost line heave, and a heaved deck racks the frame, ledger and stairs together.

What joist spacing does composite decking need?

Most capped composite requires 16 inches on centre for perpendicular installation and 12 inches on centre for diagonal, and some lines require 12 inches throughout. Check the specific product before framing — installing on wider spacing causes visible sag and voids most board warranties.

How long does a pressure-treated deck last?

Realistically 10 to 15 years for the decking surface with regular cleaning and resealing, and often longer for the frame if the joist tops were protected. Untreated maintenance shortens that considerably; joist tape and proper flashing extend it.

Is it cheaper to build a deck or a paver patio?

A paver patio is almost always cheaper per square foot — commonly $15 to $30 installed versus $25 to $60 for a deck. A deck wins when the ground slopes, when you want to walk out level from a raised door, or when excavation would be expensive. On flat ground at grade, the patio is the better value.