Guaranteed Maximum Price (GMP) Contracts: How They Work, What They Cover, and When to Use One

A guaranteed maximum price contract is a construction agreement in which the contractor agrees that the total cost of the project will not exceed a defined ceiling — the GMP — regardless of actual costs incurred. If actual costs run over that ceiling, the contractor absorbs the difference. If costs come in under it, any savings are typically shared between the owner and contractor according to a formula negotiated in the contract.

Key components of a GMP contract:

• The GMP figure – the hard cost ceiling the contractor cannot bill beyond
• The scope of work – a detailed description of what is included; work outside this scope may justify a GMP amendment
• Allowances – line items for materials or work where costs are not yet certain
• Contingency – a reserve fund, typically held by the contractor, for unexpected field conditions or scope clarifications
• The savings-sharing clause – the formula governing how underrun savings are split
• Open-book accounting – most GMP contracts require the contractor to make cost records available to the owner

GMP contracts are common in construction manager at-risk (CMAR) delivery, where a construction manager commits to the GMP at or before the end of the design phase and assumes the risk of cost overruns thereafter.

How a GMP Contract Works: The Mechanics

Understanding the GMP meaning requires understanding the sequence of events that produces one.

1. Preconstruction Phase The contractor is typically engaged early — often before design is complete — to provide pricing input, constructability review, and phased cost estimates. This early collaboration is one of the GMP model’s defining features and a major advantage over traditional bid-build delivery.

2. GMP Proposal and Negotiation Once design reaches sufficient completeness (often 60–100% construction documents), the contractor submits a GMP proposal. The proposal itemizes estimated costs by trade, identifies allowances for undefined scope, and includes a contingency percentage. The owner and contractor negotiate the GMP figure and savings-sharing terms before execution.

3. Construction and Open-Book Accounting During construction, the contractor draws on actual subcontractor bids and invoices. The owner typically has audit rights — the ability to review cost records and verify that charges are legitimate and within scope. This transparency distinguishes GMP contracts from lump sum arrangements, where the contractor’s internal costs are opaque.

4. Project Closeout and Savings Sharing If the project is delivered under the GMP, the remaining balance is split per the contract formula. A common arrangement is 50/50 between owner and contractor, though the split is fully negotiable. This shared savings mechanism aligns the contractor’s incentives with the owner’s interest in cost efficiency.

GMP vs. Other Construction Contract Types

GMP vs. Lump Sum (Fixed Price)

Factor	GMP Contract	Lump Sum Contract
Cost ceiling	Yes – contractor cannot exceed GMP	Yes – fixed price regardless of cost
Owner visibility into costs	High – open-book accounting	Low – contractor’s costs are private
Shared savings	Yes, if negotiated	No
Flexibility for changes	High – change orders adjust GMP	Low – changes lead to disputes
Best for	Complex or phased projects	Well-defined, fully designed projects

A lump sum contract offers a fixed number, but that number is typically inflated by contractor contingency built in to protect against uncertainty the contractor cannot see. A GMP contract often produces a lower cost ceiling on complex projects because contingency is transparent and controlled rather than buried.

GMP vs. Cost-Plus

A cost-plus contract reimburses the contractor for all actual costs plus a fee — with no ceiling. The owner bears unlimited cost risk. A GMP contract preserves the open-book transparency of cost-plus while adding a hard cap that transfers cost overrun risk to the contractor. For sophisticated owners, a GMP with a shared savings clause is generally preferable to a pure cost-plus arrangement on any project where budget certainty matters.

GMP vs. Fixed Price with Contingency

Some owners attempt to achieve budget certainty through a fixed price contract with a large owner-side contingency. This approach places contingency control with the owner rather than the contractor, which can be advantageous – but it also requires the owner to manage draw-down and approval, adding administrative burden. A well-drafted GMP contract can distribute this responsibility more efficiently.

What Is Included in the GMP Figure?

A GMP typically encompasses:

• Direct construction costs — labor, materials, equipment
• Subcontractor costs — all trade work let by the contractor
• General conditions — project management, site supervision, temporary facilities, insurance
• Contractor’s fee — profit and overhead, stated as a fixed fee or percentage
• Contingency — typically 3–10% of construction cost, held by the contractor for unknown conditions within the defined scope

What is generally not included in the GMP: owner-furnished items, permit fees (unless specified), design fees, owner’s contingency for scope changes, and costs arising from owner-directed changes. These items should be addressed explicitly in the contract.

GMP Amendments and Change Orders

A GMP amendment (sometimes called a change order to the GMP) adjusts the maximum price ceiling when the owner directs work outside the original scope, when unforeseen conditions arise that fall outside the contractor’s contingency, or when design changes alter the project materially.

GMP amendments are a common source of disputes. Contractors sometimes assert that scope has changed to justify GMP increases; owners sometimes dispute whether the changed condition falls within the contractor’s contingency or outside it. Clear contract language defining the scope, the contingency purpose, and the change order process is essential to preventing these disputes.

Best practices for managing GMP amendments:

• Define scope in the contract with precision — vague scope language benefits the contractor
• Specify what the contingency covers (and what it does not)
• Require written authorization before any work outside scope begins
• Establish a timeline for change order pricing and approval

Risk Allocation in a GMP Contract

One of the GMP contract’s primary functions is to allocate financial risk between the owner and contractor. Understanding this allocation is critical before signing.

Contractor bears:

• Cost overruns caused by inefficiency, subcontractor underperformance, or errors in the GMP estimate
• Field conditions within the defined scope that exceed the contingency

Owner bears:

• Cost increases from owner-directed scope changes
• Design errors or omissions (if the designer is owner-contracted)
• Unforeseen site conditions that are genuinely outside the scope (depending on contract language)
• Force majeure events and material price escalation (terms vary by contract)

This allocation is negotiable. Sophisticated owners with strong legal counsel often push to limit the categories of events that justify a GMP amendment, while contractors push for broader carve-outs. The negotiation of these terms is where a construction attorney provides substantial value.

Who Should Use a GMP Contract?

GMP contracts are best suited for:

• Complex or phased projects where full design is not complete at the time of contracting
• Historic renovations where unforeseen conditions are likely
• Institutional and commercial development where budget certainty is a financial covenant requirement
• Public-private partnerships and tax credit projects where cost certification is required
• Projects where owner-contractor collaboration during design adds value

GMP contracts are generally not the right choice for:

• Small, fully designed projects where competitive lump sum bidding produces better pricing
• Projects where the owner lacks capacity to review open-book cost records
• Situations where the contractor is not experienced with GMP delivery

GMP Contracts in Florida: What Project Owners Need to Know

Florida’s construction market presents specific conditions that make GMP contracts particularly relevant.

Material price volatility. Florida’s exposure to hurricane season, supply chain disruption, and population-driven demand creates significant material cost uncertainty. GMP contracts with well-drafted escalation clauses can protect owners while giving contractors a defined path to relief when prices move materially.

Labor market conditions. The Tampa Bay metro and broader South Florida market have experienced sustained labor cost pressure. Contractors building GMP estimates in this environment may include larger contingencies. Owners should scrutinize contingency size and negotiate savings-sharing terms that create meaningful incentive for the contractor to manage labor costs.

Lien law exposure. Florida’s Construction Lien Law (Chapter 713, Florida Statutes) applies regardless of contract type. A GMP contract does not insulate an owner from lien exposure if subcontractors and suppliers go unpaid. Payment provisions in the GMP contract — and compliance with Florida’s notice and payment procedures — must be addressed alongside the GMP structure itself.

CMAR on public projects. Florida authorizes construction manager at-risk delivery for public projects under Section 255.103, Florida Statutes. Public owners using CMAR delivery should understand that the GMP negotiation process in the public context involves specific transparency and approval requirements distinct from private projects.

The Role of a Construction Attorney in GMP Contracts

A GMP contract is not a standard form transaction. The variables — contingency size, savings-sharing formula, scope definition, change order procedures, audit rights, and risk allocation — are all negotiated, and the outcomes of those negotiations have material financial consequences.

A Florida construction attorney experienced in GMP contracts can:

• Review and negotiate GMP proposals to ensure the contingency is appropriate and the scope is clearly defined
• Draft or revise contract language to close gaps that expose the owner to amendment risk
• Advise on audit rights and open-book accounting procedures
• Represent owners in GMP amendment disputes, including disputes over whether a change order is warranted
• Address lien exposure in parallel with the GMP structure
• Advise on CMAR procurement requirements for public owners

Key Takeaways

• A guaranteed maximum price (GMP) contract sets a hard ceiling on what an owner pays for construction; cost overruns above that ceiling are the contractor’s responsibility.
• GMP contracts include a contingency fund, open-book accounting, and typically a shared savings clause that rewards cost efficiency.
• Compared to lump sum contracts, GMP contracts offer more transparency; compared to cost-plus contracts, they offer more cost certainty.
• The scope definition and contingency language are the most negotiated — and most litigated — provisions in a GMP contract.
• A GMP amendment adjusts the ceiling when the owner directs changes outside the original scope; controlling amendment exposure requires precise contract drafting.
• Florida-specific factors — lien law, material volatility, CMAR statutes — require GMP contracts to address issues beyond the standard GMP framework.
• Engaging a construction attorney before signing a GMP contract is a cost-effective way to protect the owner’s financial position throughout the project.

FAQ Section

What does GMP stand for in construction? GMP stands for Guaranteed Maximum Price. It refers to a construction contract in which the total amount the owner pays cannot exceed a defined ceiling, regardless of the contractor’s actual costs.

What happens if construction costs exceed the GMP? If actual project costs exceed the GMP, the contractor is responsible for covering the difference — provided the overrun results from work within the original scope. If the owner directed additional work or unforeseen conditions fall outside the defined scope, the contractor may be entitled to a GMP amendment increasing the ceiling.

What is the difference between a GMP contract and a lump sum contract? Both types cap the owner’s cost exposure, but a GMP contract requires open-book accounting — the owner can see actual costs — and includes a shared savings clause if the project comes in under budget. A lump sum contract is a single fixed number; the contractor’s internal costs are private, and there is no savings sharing.

What is a GMP amendment? A GMP amendment is a formal modification to the guaranteed maximum price, typically issued when the owner directs work outside the original scope or when a defined unforeseen condition exceeds the contractor’s contingency. GMP amendments are a frequent source of construction disputes and should be governed by precise contract language.

How are savings shared in a GMP contract? If the project is completed for less than the GMP, the difference between actual cost and the GMP ceiling is divided between the owner and contractor per a formula in the contract. A 50/50 split is common, but the ratio is negotiable. The savings-sharing clause creates a financial incentive for the contractor to manage costs efficiently.

What is included in a GMP figure? A GMP typically includes direct construction costs (labor, materials, equipment), subcontractor costs, general conditions, the contractor’s fee, and a contingency reserve. It generally does not include owner-directed scope changes, permit fees (unless specified), design fees, or owner-furnished items.

Is a GMP contract right for every construction project? No. GMP contracts are best suited for complex, phased, or partially designed projects where early contractor collaboration adds value. For small, fully designed projects, competitive lump sum bidding often produces better pricing. The right contract type depends on project complexity, schedule, design completeness, and the owner’s capacity to manage open-book accounting.

Do Florida lien laws apply to GMP contracts? Yes. Florida’s Construction Lien Law (Chapter 713, Florida Statutes) applies regardless of contract type. GMP contracts do not insulate owners from lien exposure if subcontractors or suppliers go unpaid. Owners should ensure that GMP contracts address Florida’s payment and notice requirements explicitly.

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Southron Firm, P.A. represents property owners, developers, and businesses in construction contract negotiation, GMP review, and construction dispute resolution throughout Florida. This article is provided for informational purposes and does not constitute legal advice. Contact our Tampa office to discuss your project.