Second-story deck cost

A second-story deck costs $70 to $150 per square foot, typically around $100, against $30 to $65 for the same surface built in pressure-treated wood a step off the lawn. The boards and joists are much the same. What roughly doubles the price is everything holding them eight to twelve feet in the air.

Height is the one thing that moves it. Every extra foot lengthens the posts, adds bracing, adds risers to the stair and, past a point, puts an engineer's name on the drawings.

What it costs

The elevated rate is a whole-deck figure, footings to guard with one stair run, not a premium added to the ground-level rate. The bottom is a plain treated deck about eight feet up on level ground; the top is capped composite with cable or glass guards.

Where the extra money goes

Two quotes for the same 12 by 16 surface, one at grade and one at the second story, share the joists and boards. The difference sits in four places.

Posts and bracing. A low deck sits on short posts. At ten feet the posts are columns, and most current code tables limit 4x4 posts to short decks and call for 6x6 posts at this height. Tall posts also need knee braces, or a design that does without them, because a post that can rack will.

Footings. An elevated deck usually has fewer, more heavily loaded posts so the space underneath stays open. That means bigger footings, dug below the local frost line, with more concrete in each hole and more digging next to the foundation, where the soil was backfilled when the house went up.

Working at height. Every beam is lifted, set and fastened from ladders, scaffolding or a lift. Framing a deck you can step onto from the grass is quick; framing one at the height of the gutters is slow, and the crew's insurance costs more for the same reason.

The stair. A ground-level deck has two or three steps. A second-story deck has a real staircase, often with a landing, and it is frequently the largest single addition to the quote.

The connection to the house

On a deck this high the house carries half the structure. The deck cost guide explains why the ledger matters on any deck; at the second story there are three details to see on the quote by name.

Bolts, not nails. The ledger should be fastened to the house rim joist with half-inch lag screws or through-bolts in a staggered pattern, or with structural screws rated for ledgers. Nails alone do not pass in most jurisdictions, and most codes do not allow a ledger hung on brick or stone veneer or on a cantilevered floor overhang at all.

Lateral load connection. A ledger stops the deck dropping. It does much less to stop the deck pulling away from the wall when a crowd moves on it. Most current codes add hold-down tension devices near each end of the deck, tying the deck joists through the rim to the floor framing inside the house. That can mean opening a ceiling in the room below, and the quote should say who patches it.

Flashing. The siding comes off where the ledger goes, a self-adhered membrane goes onto the sheathing, and a flashing laps over the top of the ledger and up under the siding above. Water behind a ledger rots the rim joist that is holding the whole deck, and at this height nobody sees it until a board gives.

Where the house cannot take a ledger, the deck can be freestanding: a second beam and post line along the house wall, so the deck stands entirely on its own footings. It costs more in posts and concrete and saves the siding work and the lateral connection. On brick, stucco, or an older house with framing nobody can verify, it is often the better design.

When an engineer is needed

Most decks are built from prescriptive tables. The code, or a deck guide the jurisdiction adopts, sets joist spans, beam sizes, post sizes and footing sizes, and the inspector checks the deck against them. A deck that fits the tables usually needs no engineer.

Elevated decks fall outside the tables far more often. The common triggers:

• Post heights beyond what the tables cover
• Long beam spans, chosen to keep the patio underneath free of posts
• A hot tub, or a heavy planter, outdoor kitchen or masonry fireplace
• Cantilevers past the table limits, or a deck wrapping a corner of the house
• Filled or poor soil, or a sloped lot where the downhill posts are far taller than the uphill ones
• No ledger possible and no room for a second post line

An engineer's letter or design for a deck usually sits toward the lower end of $400 to $1,500, and it gives every bidder the same framing plan to price. The structural engineer guide covers finding one who works for you rather than for a builder.

The stair, and the space underneath

A stair down from a ten-foot deck is not a few steps. With risers kept under the usual code limit of about 7 3/4 inches, a ten-foot rise needs around 16 risers, and the flight runs 12 to 13 feet out into the yard. Most codes also cap the height one flight can climb at a little over 12 feet before a landing is required, and a landing needs its own posts and footings.

Turning the stair at a landing pulls it back toward the house, at the cost of a platform, more guard and two more footings. Ask for a drawing showing where the bottom step lands; on a narrow lot it can end across a walkway or inside a side setback.

The space under a second-story deck is an outdoor room with a leaky ceiling. Rain falls straight through the board gaps onto whatever is below. Under-deck drainage systems that catch water between the joists are quoted separately, and they are far cheaper to fit before the boards go down than after. The framing is also on view from below for as long as the deck stands, so ask whether beams will be clean stock and the hardware neatly set.

A worked example: a 12 by 16 deck off a second-story kitchen

The kitchen sits at the second story over a walkout basement, with bare dirt where a patio should be. The owner wants 192 square feet at about ten feet, treated framing with composite boards and a straight stair, and the long beam span over the patio needs an engineer's letter.

• Deck, footings to guard: 192 sq ft × $70 to $150 per sq ft = $13,440 to $28,800
• Engineer's letter: $400 to $1,500
• Patio under the deck: 192 sq ft × $8 to $26 per sq ft = $1,536 to $4,992
• Total: $15,376 to $35,292

The deck line alone, $13,440 to $28,800, is more than twice what the same footprint costs built in treated wood at grade. The patio is optional, and it is cheapest poured before the deck exists, while a truck can still reach the spot.

Two things are not in the total. If the kitchen has a window where the door should be, a new opening with a header sized for the wall above is quoted separately by a framer, and the drainage system under the joists is its own line.

Reading an elevated deck quote

A sound quote for a deck at this height answers these in writing:

• What size are the posts and footings, and how deep do the footings go?
• How is the lateral load connection made, and does it need access from inside?
• What flashing goes behind and over the ledger?
• Is the frame built from the code tables or from an engineer's design?
• How many risers does the stair have, does it need a landing, and where does it end?
• What guard is included, and to what height? The deck railing guide has the code figures.

Frequently asked questions

How much does a 12x12 second-story deck cost?

That is 144 square feet at $70 to $150 a square foot, before engineering, a new door or drainage underneath. Small elevated decks land toward the top of the per-foot range, because the stair, the ledger work and the corner posts cost about the same whatever the area.

Is composite worth it on an elevated deck?

Usually more so than at ground level. The boards are a smaller share of an elevated deck's price than of a low one, so composite adds proportionally less, and refinishing a deck ten feet up means staining from ladders. At grade the gap is wider: $30 to $65 against $40 to $100 a square foot.

Can a second-story deck be built without attaching it to the house?

Yes. A freestanding deck carries its house side on its own beam and posts, a few inches off the wall. It needs more footings, but no ledger, no lateral connection and no opening in the siding, which makes it the usual answer on brick, stucco or a wall with no accessible rim joist.

Do I need a permit for a second-story deck?

In practically every jurisdiction, yes, and the inspector will want to see the footing holes before concrete and the ledger before it is covered. An unpermitted elevated deck is also the kind of thing a buyer's inspector flags first, because a failure at that height is a serious injury.

Related guides

• Deck cost — ground-level decks by material and size
• Composite deck cost — board tiers and re-decking a sound frame
• Deck railing cost — the guard code and the 200 pound load
• Structural engineer cost — what an independent report buys
• Concrete patio cost — the slab that often goes under a raised deck