How to Estimate a Deck: Framing, Decking, Footings, and Railings

The client shows you their backyard and asks for a 400 SF deck. You picture the decking boards, do some quick math, and land on a number. Then the project starts and you remember: footings, ledger board, joist hangers, post hardware, railing posts, and two flights of stairs. Those "extras" are half the labor and a third of the material cost.

A deck estimate has five independent scopes: footings, framing, decking surface, railings, and stairs. Each one has its own material and labor calculation. Do them separately and your number holds. Blend them into a per-SF rate and you are pricing off hope.

The Full Cost Breakdown

Installed wood deck cost runs $25–$45/SF for pressure-treated framing with PT or cedar decking. Composite decking (Trex, TimberTech) adds $8–$15/SF to material. Here is the full scope:

• Concrete footings: $150–$350 each installed. A standard 400 SF deck needs 6–10 footings depending on span, load, and local code. Auger rental and concrete pour are the main costs. Rocky soil adds labor time. Inspect the footing locations before you dig — utilities, root systems, and irrigation lines all move your hole.
• Framing lumber (beams, joists, posts): $2.50–$4.50/SF of deck area. Pressure-treated 2x10 joists at 16-inch on-center, doubled beams, and 4x4 or 6x6 posts. Lumber prices fluctuate — always price from your current supplier quote, not last year's job.
• Ledger board and house attachment: $8–$14 per linear foot. Flashing, lag screws, and caulking. Often overlooked as a separate line item. A 16-foot-wide deck has a 16-LF ledger — price it separately.
• Decking boards: $3.50–$6.00/SF for pressure-treated pine. Cedar runs $5.00–$8.00/SF. Composite (Trex Enhance) starts at $7.00/SF; Trex Transcend or TimberTech Azek runs $10–$14/SF. Add 10% waste for cuts, end-matching, and board defects.
• Hardware (joist hangers, post caps, screws, bolts): $0.80–$1.40/SF of deck area. This is a real cost that disappears into "materials" on most estimates. Price it line by line on your first couple of decks — then you will know your number.
• Railings: $45–$120 per linear foot installed, depending on material. PT wood balusters at code spacing is the low end. Cable railing (Feeney DesignRail) or aluminum picket systems land at $80–$120/LF. Measure railing perimeter separately — it is the most common underpriced line item on deck bids.
• Stairs: $200–$600 per stair tread, depending on width, material, and number of rises. A single 4-foot-wide stair run with 8 risers costs $1,600–$4,800 to build. Stairs take disproportionate labor — price each flight as a separate scope item.
• Permit: $300–$900 depending on jurisdiction. Always verify permit requirements before bidding. Some municipalities require stamped engineering drawings on decks over 30 inches above grade. That is a separate cost that belongs in the estimate, not in your overhead.

Where Deck Estimates Break Down

Footing count and depth. Local frost depth and soil bearing capacity determine footing size. A footing for a deck at 2 feet of elevation is different than a footing for an 8-foot-high elevated deck. Know your code requirements before you count footings.

Railing linear footage. The deck is 400 SF. The railing is whatever the perimeter minus the house wall comes out to. On a deck that projects 20 feet from the house and is 20 feet wide, railing runs 60 LF, not a percentage of 400 SF. Always measure it.

Composite upsells. Composite decking is a premium add-on that carries better margins and clients often say yes when you show them the 25-year warranty against fading and splinters. Price it as an explicit option — not a default. A 400 SF deck upgrade from PT to Trex Transcend adds $2,800–$4,000 in material. Your margin on that upsell should be substantial.

Labor: How Long Does a Deck Take?

A 400 SF deck with an experienced two-man crew typically takes 4–6 days. Here is a rough breakdown:

• Footings: 4–8 hours depending on count and soil. Hard rock adds significant time.
• Framing: 10–16 hours for posts, beams, and joists. Elevated decks add time for post-setting and bracing.
• Decking boards: 8–14 hours for 400 SF depending on board width and whether you are using hidden fasteners. Hidden fasteners add 20–30% to decking labor.
• Railings: 6–12 hours for 60 LF of standard PT railing. Cable railing adds 30–50% to installation time per linear foot.
• Stairs (one flight): 4–8 hours. Each additional flight adds proportionally.

"Stairs kill schedules. Price each flight as its own scope item, not a percentage of the deck."

Frequently Asked Questions

What does a deck cost per square foot installed?

Pressure-treated wood decks run $25–$35/SF installed. Cedar decks land at $30–$45/SF. Composite decking (Trex, TimberTech) adds $8–$15/SF to those numbers. Railings and stairs are not included in per-SF rates — price them separately by linear foot and per flight.

How much do deck footings cost?

Each footing runs $150–$350 installed, including auger time, tube form, concrete, and post hardware. A standard 400 SF deck needs 6–10 footings. Count them from your structural layout — do not estimate footing count from square footage.

What does deck railing cost per linear foot?

PT wood railing with code-compliant balusters runs $45–$65/LF installed. Aluminum picket systems (Fortress, Westbury) land at $70–$95/LF. Cable railing (Feeney DesignRail) runs $95–$120/LF. Measure your railing perimeter from the plan — do not derive it from deck square footage.

Should I include a permit in my deck estimate?

Yes — always. Most jurisdictions require a permit for decks over 200 SF or over 30 inches above grade. Pull it or have the homeowner pull it, but price it. Permit fees run $300–$900 depending on jurisdiction. Unpermitted decks create liability for you when the home sells.