Deck Contractor Red Flags: 12 Warning Signs to Check Before You Sign
Deck structural shortcuts are invisible until something fails. These are the flags — built from analyzing 136 real homeowner bids — that separate solid builds from expensive problems.
Have a deck bid?
BidLens checks all 12 flags — material spec, structural compliance, payment terms, and markup — free.
Analyze my deck bid free →1. No ledger flashing specified
Ledger flashing is required by IRC R507.2.3 and is the single most commonly skipped item in deck bids. Without a continuous waterproof barrier between the ledger board and house wall, water infiltrates the framing, causing rot that can cost $10,000–$30,000+ to fix — often years after the deck is built.
Add to scope: "Continuous ledger flashing per IRC R507.2.3, installed under house cladding and over ledger."
2. 24" OC joist spacing with composite decking
Most composite decking products (Trex, TimberTech, AZEK) require 16" OC joist spacing. Installing at 24" OC voids the manufacturer warranty and causes deck boards to deflect, bounce, and gap over time. This is one of the most common structural shortcuts.
Require: "Joists at 16" OC per manufacturer installation requirements." Verify against your specific product's installation guide.
3. No footing specifications
Footings must extend below the frost line per IRC R507.3 — ranging from 12 inches in Florida to 60 inches in Minnesota. Shallow footings heave, shift, and fail. A bid that says "footings as required" without specifying depth and diameter is not a spec.
Require: footing depth (below local frost line), diameter (minimum 12"), and concrete PSI (minimum 2,500 PSI, 3,000 in freeze-thaw zones).
4. Material spec vague — "composite decking" only
Composite decking spans Trex Enhance Basics ($4.50/sqft) to Trex Transcend Lineage ($17/sqft). "Composite decking" without a product line allows substitution after signing. On a 400 sqft deck the difference is $5,000+ in materials.
Require: exact manufacturer, product line, and color in writing. Example: "Trex Transcend, Havana Gold, 5/4x6 boards."
5. Lump sum with no material/labor breakdown
Without line items for materials, labor, demo, permits, railing, and stairs, you cannot compare bids, verify markup, or identify scope gaps. The BidLens markup formula requires itemized costs.
Request separate line items for: decking material, framing, railing (with LF), stairs (per set), demo, permits, hardware, and labor.
6. No railing spec — type, brand, LF count
Railing cost spans $20–$250/LF installed depending on type. Cable railing ($80–$150/LF) vs. wood railing ($20–$60/LF) on 60 LF is a $3,600–$5,400 difference. "Railing included" without a spec is not a spec.
Require: railing type (aluminum/cable/composite/wood), brand, and linear footage count.
7. No stair specification or count
Each set of stairs costs $1,500–$4,000. A lump sum bid that mentions stairs without specifying count and configuration can exclude or include them ambiguously. Change order territory.
Require: number of stair sets, width, rise/run, and whether railing is included on stairs.
8. 4×4 posts on elevated deck over 8 feet
IRC R507.4 limits 4×4 posts to 10 feet maximum height. For elevated decks where post height approaches or exceeds 8 feet, 6×6 posts are standard practice. Undersized posts on elevated structures are a safety issue.
Ask: "What post size are you using and what is the maximum post height?" Any deck over 6 feet high should spec 6×6 posts.
9. No demo or debris removal mentioned
Removing an existing deck costs $1,000–$3,000 and is frequently missing from bids. If demo is not in the bid, clarify who handles it — verbally agreeing creates disputes.
Add to scope: "Remove and dispose of existing deck structure including all framing and hardware."
10. No permit mentioned for attached/elevated deck
Most jurisdictions require permits for attached decks and elevated decks. An unpermitted deck can fail home inspection at sale, void homeowner's insurance, and create structural liability.
Ask: "Are you pulling the building permit?" This must be yes for any attached or elevated deck.
11. No joist hanger or structural hardware mentioned
IRC requires approved connectors at joist-to-beam and beam-to-post connections. Toe-nailed connections alone are not code-compliant. Missing hardware is a common budget shortcut.
Add to scope: "All joist-to-beam connections to use Simpson Strong-Tie or equivalent approved hangers per IRC R507."
12. Cash only or no written contract
A verbal deck agreement has no legal standing. Cash-only payments eliminate your paper trail, dispute options, and card protection. Both patterns are common among unlicensed deck builders.
Require a signed written contract before any payment. Pay by check or credit card only.
BidLens checks all 12 deck flags automatically
Upload your deck bid and BidLens checks material spec, structural code compliance, payment terms, and markup — against real regional pricing data from 136 homeowner projects.
Analyze my deck bid free →Frequently Asked Questions
What are the biggest red flags in a deck contractor bid?+
Why is ledger flashing so important for decks?+
Related Guides
Deck Cost Guide: Real Data
Regional pricing from 136 real homeowner projects.
Contractor Red Flags: 26 Warning Signs
The complete list across all project types.
How to Compare Contractor Bids
Level scope, verify materials, calculate markup.
What Should a Contractor Bid Include?
Every line item a deck bid must have.