How to Compare Deck Contractor Bids (The Line Items Most Homeowners Miss)

Three deck bids come in: $18,000, $24,000, and $21,500. All three say “400 sq ft composite deck with railing.” That $6,000 spread on what sounds like the same project is not an accident — it's a scope gap you won't find until you know exactly what to look for.

Deck bids are among the easiest for contractors to manipulate because so many critical decisions — footing depth, joist spacing, fastener type, railing brand — sound like technical details but determine both cost and longevity. Here's how to read a deck bid like a builder.

Why are deck contractor bids so different from each other?

Deck bids diverge primarily on structure and material specification, not labor rates. One contractor prices frost-depth concrete footings; another plans to use deck blocks on grade. One specs 16-inch on-center joist spacing; another uses 24-inch to reduce lumber count. One includes hidden fasteners; another uses exposed screws. Each of these choices affects both cost and how long the deck lasts — and they're easy to obscure in a lump-sum bid.

Material selection alone can swing a bid by $8,000–$15,000 on a 400 sq ft deck. Pressure-treated wood runs $25–$60 per installed square foot. Mid-grade composite runs $50–$90 per square foot. Premium composite or tropical hardwood runs $90–$140 per square foot. A bid that doesn't name the specific decking product is a bid you can't evaluate accurately.

Permits are another hidden variable. Deck permits cost $150–$1,500 depending on jurisdiction and project size. Any deck attached to the home, elevated more than 30 inches, or over 200 square feet almost certainly requires a permit in most states. A bid without a permit line either expects you to pull it yourself (you can't, for contractor work) or is planning to skip it.

What should a deck bid include?

A complete deck bid should itemize: footing count, diameter, and depth (must reach below local frost line), post and beam species and dimensions, joist size and spacing (16 vs. 24 inches on-center), decking material by manufacturer and product line, fastener system (hidden clip vs. exposed screw with specific brand), railing system by brand and style, ledger attachment and flashing method, stairs and landing (often excluded by default), permit and inspection fees, demolition of an existing deck if applicable, and cleanup and debris hauling.

Footing depth deserves special attention. A deck without frost-depth footings will heave as the ground freezes and thaws — often within three to five years. The IRC requires footings to extend below the frost line, which ranges from 0 inches in Miami to 60 inches in northern Minnesota. Ask every bidder: how deep are the footings, and how many? If a bid is vague on this, the footings are probably wrong.

Stairs are frequently excluded from bid totals even when the scope description implies they're included. A standard deck staircase adds $700–$2,500 depending on height and width. Before comparing totals, confirm whether each bid includes stairs, how many, and with what railing.

What are the biggest red flags in a deck bid?

A lump-sum bid with no material specifications is the clearest red flag. If a contractor can't or won't specify the decking product by manufacturer and line, the joist spacing, or the footing depth, you have no basis for evaluating the bid and no contractual protection if they cut corners once work starts.

Other red flags worth watching:

• No permit line item. Most deck projects require a permit. A bid without one is planning to skip it — which can trigger stop-work orders and create problems at resale.
• Decking material listed as “composite TBD.” There is a $30–$50 per square foot difference between entry-level and premium composite. “TBD” means the cheapest available wins after you sign.
• Footings described as “per local code” without specifics. This is technically defensible but tells you nothing. Get a footing count and depth in writing.
• Ledger attachment not mentioned. A deck attached to the house without proper ledger flashing is a water intrusion problem waiting to happen. If the bid doesn't address the ledger, ask directly.
• Railing specified as “standard.” Railing systems range from $30 to $200+ per linear foot installed. “Standard” means the cheapest available, with no warranty.

How do I normalize deck bids for a fair comparison?

Create a spreadsheet with one row per line item and one column per contractor. When a bid omits a line item that others include — stairs, permit, demolition of the old deck — add the cost of that item to their total before comparing numbers. A bid that is $3,000 cheaper may be pricing a shallower footing system, lower-grade composite, and no permit — none of which shows up in the bottom line.

Once scope is normalized, compare these five things directly: (1) footing depth and count, (2) joist size and spacing, (3) decking product by name, (4) railing system by brand and linear footage included, (5) warranty — both on materials and on the contractor's workmanship. A legitimate deck contractor should offer at minimum a two-year workmanship warranty. Premium composite manufacturers like Trex and TimberTech offer 25–50 year material warranties, but those warranties require licensed installation to be valid.

Does a deck contractor need to be licensed?

In most states, yes. Deck construction involves structural work — footings, framing, ledger attachment to the home's structure — that requires a licensed general or residential contractor in states with licensing requirements. The specific license classification varies: California requires a Class B General Building Contractor from the CSLB; Florida requires a licensed Building Contractor or Residential Contractor from the DBPR; most other states with licensing requirements route deck work through their general contractor license.

An unlicensed contractor cannot legally pull a permit. Unpermitted deck work means no inspection, no verified code compliance, and a disclosure problem when you sell. It can also void the manufacturer warranty on composite decking — most manufacturers require licensed installation. And if an unlicensed worker is injured on your property, you may bear personal liability since they likely carry no workers' compensation insurance.

How do I verify a deck contractor's license before accepting a bid?

Ask each bidder for their license number during the bidding process — before price is on the table. Then search your state's contractor licensing board by that number. Confirm: the license is currently active, the classification covers residential structural construction, and there is no disciplinary history or unresolved complaints.

State license databases are free. Active status with no complaints is the baseline. If a contractor has prior disciplinary actions — especially for permit violations or abandoned projects — remove them from consideration before price matters. CheckLicensed's free bid comparison tool is built for this moment: you have bids in hand, you want to verify each contractor, and you want to normalize scope before the contractor knows you're comparing.

Verify on the day you sign, not the day you got the bid. A contractor license can expire between estimate and contract. One check at signing costs nothing and eliminates the most common source of deck project disputes.