Use this worksheet before you sign anything. The seven questions below decide whether a cost plus contract genuinely fits your project — or whether you’re about to hand the contractor an open checkbook.
Quinn says
A fixed price contract names a number. A cost plus contract names a method. Most homeowners don’t realize how big that distinction is until the bills start rolling in 50% over estimate. Work through this worksheet honestly. If your honest answers point one way, listen to them.
Concept 01
What a cost plus contract actually is
A cost plus contract — also called time and materials — reimburses your contractor for every project expense (labor, materials, subcontractors, equipment, disposal, even the porta-potties) and adds a profit margin on top. The industry calls this open book: every receipt is shared. The upside is full transparency. The downside is every dollar you see is a dollar you’re paying.
Cost plus comes in three distinct flavors. The structural difference between them decides who carries the risk.
Most risk to you
Cost Plus Percentage
The fee is a percentage of total costs (often 15–25%). If costs go up, the contractor’s profit goes up. The incentive to keep your project lean is structurally backwards.
Kitchen remodel costs $130K at 15% → fee is $19,500. If costs hit $175K → fee jumps to $26,250.
Better protection
Cost Plus Fixed Fee
A flat dollar management fee agreed upfront, regardless of total costs. Removes the worst of the incentive misalignment — the contractor doesn’t gain extra fee if costs rise.
$400K renovation with a $25,000 fixed management fee. That fee doesn’t move whether costs land at $400K or $475K.
Safest hybrid
Cost Plus + GMP
Cost plus billing with a Guaranteed Maximum Price ceiling. If costs go over the cap, the contractor absorbs the overrun unless scope changes. Standard in commercial work (AIA A102).
Cap set at $150K. If actual costs would have been $170K, the contractor eats the $20K difference.
Concept 02
What the markup actually costs you
Industry-standard markup on residential cost plus runs 10% to 25%, with 15–25% most common. That fee covers the contractor’s overhead, insurance, supervision, tools, trucks, payroll, office, and profit. Not unreasonable — but you should know what you’re paying for.
Project size
Fee at 15%
Fee at 20%
Fee at 25%
$200,000
$30,000
$40,000
$50,000
$300,000
$45,000
$60,000
$75,000
$500,000
$75,000
$100,000
$125,000
$1,000,000
$150,000
$200,000
$250,000
Quinn’s warning
A contractor offering well below the typical range — say 6% instead of 15% — might be legitimate. Or they might be planning to recover the difference inside the cost line items: hidden subcontract markups, materials handling charges, tool rental fees. Ask for full disclosure of how every dollar moves through the project.
Concept 03
The California surprise
In California, a pure cost plus contract for residential home improvement work is illegal. The citation: California Business and Professions Code Section 7159.5. A licensed contractor cannot enter into a cost plus contract for the performance of home improvement work — the law requires a fixed total price, a payment schedule tied to completed work in dollars and cents, and consumer-protection disclosures.
!
What this means in practice. The CSLB can issue citations up to $5,000 per violation, suspend or revoke a contractor’s license, and the homeowner can void the contract entirely at their sole discretion. Exemptions exist for new construction on vacant land, small service and repair work, commercial projects, and jobs under $500. Even outside California, the underlying issue is the same — cost plus shifts financial risk to the homeowner. The legal landscape just changes the urgency. Not legal advice — consult a construction-law attorney for your specific situation.
Concept 04
The five drift triggers that push you into cost plus
A project doesn’t always start as cost plus. Sometimes it ends up there because of choices made before the first contractor walked through the door. Watch for these five.
1
Incomplete plansThe contractor literally cannot price what isn’t drawn. Plan quality drives contract structure.
2
Thin or missing specificationsWithout specs, the contractor is guessing on materials, finishes, scope. Cost plus fills the vacuum.
3
Scope changes mid-decisionEvery undecided choice forces the contract toward “we’ll figure it out as we go.”
4
The rush to start“I just want to get started” is the biggest predator of budget control there is.
5
Price not a high prioritySometimes legitimate. Sometimes a warning sign. Either way, it opens the door.
A complete bid package is the structural antidote to drift. Without one, you’re already halfway into cost plus before anyone has used the words.
Concept 05
Who cost plus genuinely works for
Cost plus isn’t always wrong. There’s a narrow band where it’s the right structural choice. Most homeowners are not in this band.
1
The very experienced homeowner
Built or remodeled multiple times. Knows construction billing. Has the time and discipline to manage the books closely. Catches the inefficiencies a fixed price would hide inside the margin.
2
The truly indifferent homeowner
Genuinely doesn’t prioritize total cost, or has a project so small the bidding overhead doesn’t make sense. Even then — comfort with billing practices is required.
3
Great craftsman, weak admin
You’ve found a phenomenal builder who can’t run an office. If you have the time and skill to manage the books for them, cost plus can deliver the highest-quality result you’ll ever own.
Disaster rebuild exception
If you’re rebuilding after a fire, flood, or other catastrophe, your contract is almost certainly cost plus. Insurance reimburses documented costs as scope is uncovered, and there’s no way to know full scope until demolition exposes what’s actually damaged. Your bookkeeping discipline determines whether you actually get paid.
Concept 06 · Self-assessment
The seven questions before you sign
How to use this section. Answer each question honestly — not strategically. The verdict block at the bottom updates live as you select. There’s no perfect score; the goal is clarity. If your honest answers point toward “I want certainty, I have a deadline, I’m new to this” — cost plus is the wrong structure.
Question 1 — Cost concern
How concerned am I about the total cost of the project?
Very concerned = cost plus is the wrong structure. Cost plus trades certainty for flexibility — and certainty is what you’re after.
Question 2 — Cost certainty tolerance
How tolerant am I of not knowing the exact cost before I start?
If your honest answer is “not really,” walk away from cost plus.
Question 3 — Duration concern
How concerned am I about the duration of construction?
Cost plus structurally rewards delay. If you have a deadline, this is the wrong structure.
Question 4 — Delay tolerance
Can I tolerate delays from material supply, weather, or unforeseen complexities?
Cost plus passes those delays directly to your wallet — every day extends the bill.
Question 5 — Documentation discipline
Am I willing to invest the time and money to thoroughly document the project?
A cost plus contract managed without documentation is just a checkbook with a contractor’s name on it.
Question 6 — Contractor budget discipline
Is my contractor willing to create a budget and manage costs along the way?
If they push back on this, that’s your answer about whether to work with them at all.
Question 7 — Trust factor
Do I have a good feeling about my contractor — or am I just selecting the cheapest one?
Trust matters more in cost plus than in any other structure, because the contract itself doesn’t protect you. The contractor’s character does.
Awaiting your answers
Answer the seven questions above to see your reality check.
Each question scores 0, 1, or 2. The total is your friction score for cost plus. Lower is better.
0 of 7 answered
Enlighten, empower, protect. Now go make it happen.
— Bill Reid
Your Home Building Coach · 35+ years of residential construction
Print or save your reality check. Your selected answers and verdict will appear in the printed copy. Take it to your contractor meeting — or your kitchen table — before you sign anything.
