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Deck quotes surprise people because the deck surface is only half the bill. The railing, the stairs, the footings, and the height off the ground can add as much as the decking itself, and a bid that looks high usually just has more of those in it. The calculator below prices all of it: enter the size, pick a decking material, set the railing and stairs, and you get an installed range, a materials-only range, a board count, and a cost per square foot. Every number it uses is listed further down so you can check a real bid line by line.
Deck Cost Calculator
Where the money goes (installed)
- Deck surface and framing, 192 sq ft of Composite (Trex, TimberTech): $8,650-$13,450
- Railing, 40 linear ft: $2,800-$4,400
- Stairs, 3 steps: $450-$900
- Permit and inspections: not priced at this height
- Materials-only total (any height): $5,150-$8,450
2026 US national ranges. Railing defaults to the perimeter minus the wall the deck attaches to (40 ft here); type over it for a wraparound or a freestanding deck. Elevated decks add 15% to framing for taller posts, deeper footings, and bracing. Tearing out an old deck, lighting, and built-in benches are not included.
The Math Behind the Estimate
Square footage is length times width. A 12x16 deck is 192 square feet, a 14x20 is 280, and a 10x12 is 120. Deck pricing is quoted per square foot of walking surface, not per square foot of lumber, so the number you multiply by is the deck footprint.
Installed cost = square feet × the material rate × the height factor. The material rate is a turnkey per square foot price that already contains framing lumber, footings, fasteners, decking, and labor. The height factor is 1.00 at ground level and 1.15 for anything more than 30 inches up, because taller posts, deeper holes, and diagonal bracing all cost more per square foot of finished deck.
Railing is priced separately, per linear foot, because it has nothing to do with deck area. The calculator suggests the perimeter minus the side that attaches to the house, so a 12x16 deck with a 16-foot ledger gets 40 linear feet of railing. Change it to the full perimeter for a freestanding deck, or to zero for a ground-level platform that does not need a guard.
Stairs are priced per step at $150-$300 each. A step is one riser and one tread, so a deck 24 inches off the ground needs about four steps and a deck 48 inches up needs about seven. Deep or wide stairs, a landing, and a concrete pad at the bottom all push toward the high end.
Board count assumes standard 5-1/2 inch face decking in 16-foot lengths. One board covers 5.5 ÷ 12 × 16 = 7.33 square feet, so boards = (square feet × 1.10) ÷ 7.33. That is a 10% waste factor, which covers the cuts at each end of a run, the pieces you lose squaring up a picture frame border, and the two or three boards that arrive crowned. The quarter-inch gap between boards buys you a small extra cushion on top of the 10%. Diagonal decking earns 15% instead, and a herringbone or inlay pattern earns 20%.
2026 Deck Cost per Square Foot by Material
The gap between the materials column and the installed column is the part homeowners underestimate. Labor, framing lumber, hardware, and concrete run about 60-65% of an installed deck no matter what you walk on, which is why upgrading from pressure-treated to composite raises the total by roughly 60% rather than doubling it.
| Decking material | Materials only / sq ft | Installed / sq ft | 12x16 deck installed |
|---|---|---|---|
| Pressure-treated pine | $9-$15 | $25-$40 | $6,900-$11,400 |
| Cedar | $12-$22 | $30-$50 | $8,200-$13,900 |
| Composite (Trex, TimberTech) | $20-$33 | $45-$70 | $11,900-$18,700 |
| PVC (Azek, cellular) | $26-$42 | $55-$85 | $14,200-$22,000 |
| Tropical hardwood (ipe) | $30-$45 | $60-$95 | $15,400-$24,600 |
12x16 column includes 40 linear feet of railing and a three-step stair at ground level. Materials column covers decking, framing lumber, and fasteners with no labor.
Those per square foot rates are national 2026 averages for a straightforward rectangle attached to a house. A small deck costs more per square foot than a big one, because the fixed work (permit, ledger, stairs, mobilization) spreads over less area. A 10x10 landing deck often prices out 20-30% higher per square foot than a 16x24 on the same house.
What Actually Changes the Price
When two bids for the same deck differ by $6,000, it is almost never the decking brand. It is the items below, and the cheaper bid usually left one of them out.
| Item | 2026 cost | When it applies |
|---|---|---|
| Tear out and haul the old deck | $5-$12 per sq ft | Any replacement; includes dumpster and disposal |
| Concrete footings | $150-$350 each | One every 6-8 ft of beam, 42 in deep in northern Illinois |
| Elevated framing (over 30 in) | Add 10-20% | Taller posts, diagonal bracing, longer stair run |
| Railing | $40-$120 per linear ft | Required over 30 in; wood at the low end, cable and aluminum at the high end |
| Stairs | $150-$300 per step | A concrete landing pad at the bottom adds $300-$800 |
| Low-voltage lighting | $600-$2,500 | Post caps, stair risers, transformer, and wiring |
| Under-deck drainage system | $12-$25 per sq ft | Turns the space below an elevated deck into dry patio or storage |
| Built-in bench or planter | $400-$1,200 each | Priced per unit, framed into the deck |
| Permit and inspections | $200-$600 | Attached decks and anything over 30 in, in most towns |
Height is the biggest single multiplier. A deck 18 inches off the ground needs short posts, no railing, and two steps. Move the same deck to 6 feet up off a walkout and you have added a guardrail around the whole perimeter, a 10-step stair with a landing, taller posts on deeper footings, knee bracing, and a permit. That is easily $8,000 on a deck whose square footage never changed.
Footings and frost line. Footings have to bear below the frost line or the deck heaves every winter and pulls at the ledger. In northern Illinois, including Joliet and the rest of Will County, that means 42 inches below grade. Each hole takes roughly 1.5 to 2 bags of concrete for a 10-inch sonotube at that depth; our concrete calculator will size the pour if you are setting them yourself. Hitting clay, old fill, or a buried utility is the most common reason a deck job runs over.
Demolition. Most decks we build are replacements, and the old one has to go first. Budget $5-$12 per square foot, more if it is elevated or if the ledger was buried behind siding. On a 300 square foot deck that is $1,500-$3,600 before a single new board goes down, and it is the line item most often missing from the low bid.
Shape. Rectangles are cheap. Octagon corners, curved fascia, multi-level platforms, and a picture-frame border with mitered corners each add labor and waste. A wraparound deck can cost 25-40% more per square foot than the same area in one clean rectangle.
Composite vs Wood: The 10-Year Number
Composite costs more on day one and less every year after. The honest way to compare them is total spend over the time you actually plan to own the house, not the shelf price of a board. Here is a 12x16 deck with railing and stairs, priced at the midpoint of each range, carried out ten years.
| Material | Build cost | 10-year upkeep | 10-year total | Expected life |
|---|---|---|---|---|
| Pressure-treated pine | $9,100 | $2,800 | $11,900 | 15-20 years |
| Cedar | $11,100 | $3,000 | $14,100 | 15-25 years |
| Composite | $15,300 | $600 | $15,900 | 25-30 years |
| PVC | $18,100 | $500 | $18,600 | 30-50 years |
Upkeep assumes wood is professionally cleaned and sealed every two years at $500-$700 a cycle, plus a few replacement boards. Composite and PVC assume two washes a year with soap and water.
Read that table carefully: at year ten, pressure-treated is still $4,000 cheaper. The crossover happens around year fifteen to eighteen, when a pressure-treated deck built in 2026 is due for board replacement and a composite deck is still under warranty. If you plan to sell inside five years, pressure-treated with a good stain is the rational choice. If this is the house you stay in, composite wins, and it wins by more if you were going to pay someone else to stain.
Composite decking still needs a wood frame
A composite deck is composite boards over pressure-treated framing. The joists, beams, and posts under a 25-year deck surface are the same lumber as under a wood deck, which is why a rotted frame can outlive its warranty on the boards. Ask what the framing is: standard ground-contact treated lumber is fine, joist tape over every joist top is a cheap upgrade that roughly doubles frame life, and steel framing is a real option on high-end builds.
Permits and Code Basics
Deck code exists because decks fail in one specific way: they pull off the house. Nearly every catastrophic deck collapse traces back to the ledger, the board that bolts the deck to the rim joist. These are the items an inspector will look at, and the ones you should look at on any bid.
- Ledger attachment and flashing. The ledger must be lag screwed or through-bolted to the house rim joist in a staggered pattern, never nailed, and it needs metal flashing tucked under the house wrap and over the top of the board so water sheds outward. Missing flashing rots the rim joist from behind the siding where nobody sees it.
- Guardrail height. Any walking surface more than 30 inches above grade needs a guard at least 36 inches tall, with balusters spaced so a 4-inch sphere cannot pass through. The guard has to resist a 200-pound load at the top rail, which is why post attachment hardware matters more than the railing style.
- Stair rules. Risers max out at 7-3/4 inches and treads need at least a 10-inch run. Within a single flight, the tallest and shortest riser cannot differ by more than 3/8 inch, which is the detail that fails inspections when a stair lands on uneven ground. Four or more risers require a graspable handrail 34-38 inches above the nosings.
- Footings below frost. 42 inches in northern Illinois, with the footing inspection done before concrete goes in the hole. Once you backfill, the inspector cannot verify depth and may make you dig.
- Setbacks. Decks count as structure for zoning. Check the rear and side yard setbacks and any easement before you finalize the size, because a deck two feet into an easement is a deck you cut back.
If the bid does not name the ledger detail, ask
A real deck bid says how the ledger attaches and how it is flashed, or says the deck is freestanding on its own posts. Vague language there is the single strongest signal of a bid you should not take. The same goes for footing depth: "concrete footings" is not a spec, "10-inch tubes to 42 inches with a footing inspection" is.
One more scheduling note: deck season books up. Contractors in northern Illinois take deck deposits in February and March for May and June builds, and by July the good crews are quoting eight weeks out. If a deck is part of a larger project, sequence it with everything else using our whole-home renovation timeline, and if you are carrying the same finish inside and out, the flooring calculator handles the interior side.
Frequently Asked Questions
How much does it cost to build a deck in 2026?
Professionally built decks run $25-$40 per square foot in pressure-treated pine, $30-$50 in cedar, $45-$70 in composite, and $55-$85 in PVC, before railing and stairs. A typical 200 to 300 square foot deck with railing and a short stair lands between $8,000 and $22,000 depending on material. Materials alone are roughly 35-40% of that, so a DIY build cuts the number in half if you own the tools and the weekends.
How much does it cost to build a 12x16 deck?
A 12x16 deck is 192 square feet. Built by a contractor at ground level with 40 linear feet of railing and a three-step stair, expect about $6,900-$11,400 in pressure-treated pine, $8,200-$13,900 in cedar, $11,900-$18,700 in composite, and $14,200-$22,000 in PVC. Materials only for the same deck run roughly $2,500-$4,400 in pressure-treated and $5,100-$8,500 in composite.
What is composite decking cost per square foot?
Composite decking boards alone cost $4-$9 per square foot in 2026, and a fully installed composite deck runs $45-$70 per square foot including framing, footings, fasteners, and labor. PVC decking sits above that at $55-$85 installed. The board price is only about a quarter of an installed deck, which is why swapping wood for composite raises the total less than the shelf price suggests.
Do I need a permit to build a deck?
Almost always. Most jurisdictions require a permit for any deck attached to the house and for any freestanding deck with a walking surface more than 30 inches above grade, which is also the height that triggers a required guardrail. Permits run $200-$600 in 2026 and usually include a footing inspection before concrete and a final inspection after framing and railing. Building without one is a problem you inherit at resale, when an inspector flags an unpermitted structure attached to the house.
Is composite decking worth the extra cost?
Over ten years, yes if you hate maintenance and plan to stay. A 12x16 pressure-treated deck costs about $9,100 to build and $2,800 to keep sealed over a decade; the same deck in composite costs about $15,300 to build and $600 to maintain. Composite is still ahead on total spend at year ten, but it wins outright by year fifteen to eighteen because pressure-treated boards are usually due for replacement while composite is warrantied to 25 years or more.
Building or Replacing a Deck in Joliet or Will County?
Rehab Addicts builds decks and handles exterior work alongside interior remodels across Joliet, Shorewood, and Will County, IL, footings to 42 inches, permits pulled, inspections scheduled. See our whole-home renovation service if the deck is part of a bigger project. Free estimates.
