What Is a GMP Contract in Construction? — A GC's Guide to Guaranteed Maximum Price
A Guaranteed Maximum Price (GMP) contract is a cost-plus construction contract with a cost cap. The GC is reimbursed for all actual project costs — labor, materials, subcontractors, and general conditions — plus a fixed fee, up to an agreed-upon maximum. If costs exceed the GMP, the GC absorbs the overrun. If costs come in under, savings are typically shared between the owner and GC per a negotiated formula. GMP contracts are common on negotiated work, design-build projects, and construction manager at-risk (CMAR) delivery.
When an owner hires a general contractor before design is complete — which is increasingly common on complex, fast-track, or publicly funded work — they face a fundamental problem: how do you sign a construction contract when the drawings aren't finished yet?
The Guaranteed Maximum Price contract is the answer the industry settled on. It gives the owner a cost ceiling and predictable budget exposure. It gives the GC a revenue stream that begins before permit drawings are complete, plus the opportunity to earn a share of any savings. And it puts the two parties in a collaborative relationship — rather than the adversarial dynamic that hard bid and lump sum contracts can produce.
This guide explains how GMP contracts work, what goes inside one, where the risks sit, and what a GC needs to do to set a GMP they can actually hold.
GMP VS. OTHER CONSTRUCTION CONTRACT TYPES
To understand the GMP, it helps to place it alongside the other major contract structures GCs work under.
Lump Sum (Fixed Price)
The GC agrees to complete defined scope for a fixed price. All cost risk sits with the contractor. Common on competitively bid public work with complete construction documents. The owner pays the bid price regardless of what it actually costs the GC to build.
Cost Plus (Without GMP)
The owner pays actual costs plus a fee. No cap. All cost risk sits with the owner. Rare on private work except in emergency or disaster recovery contexts; considered too risky for most owners without a maximum price protection.
GMP (Guaranteed Maximum Price)
The GC is reimbursed for actual costs plus a fee, up to the GMP ceiling. Cost overruns above the GMP are the GC's responsibility (unless caused by owner-directed scope changes). Cost underruns are typically shared. This is the balance point: the owner has a ceiling, the GC has upside if they execute efficiently.
Time and Materials (T&M)
The owner pays for labor hours and materials at agreed rates, plus markup. Used for undefined or exploratory scopes — renovation work with unknown existing conditions, tenant improvement allowances, small projects. No cost protection for the owner.
GMP contracts are most common in these delivery methods:
- Construction Manager at Risk (CMAR): The GC is engaged early, provides preconstruction services, and establishes the GMP once design reaches sufficient completeness (typically 60–90% construction documents)
- Design-Build: The GC/design-builder proposes a GMP inclusive of design and construction
- Negotiated GC: Private owner selects the GC by qualifications or relationship, then negotiates GMP collaboratively
ANATOMY OF A GMP CONTRACT
A well-structured GMP has several defined components that together constitute the maximum price ceiling.
Direct Construction Costs
The actual cost of building: subcontractor payments, self-performed labor, materials, and equipment. These are the true project costs, documented through invoices and payroll records under the open-book accounting requirement.
General Conditions
The cost of running the jobsite: superintendent and project manager time, temporary facilities (trailer, fencing, temporary power), sanitation, site safety, testing, permits, and project-specific insurance. On a commercial project, general conditions typically run 8–12% of direct construction costs. These are usually reimbursable cost items within the GMP, not part of the GC's fixed fee.
GC Fee
The contractor's compensation for overhead and profit, typically expressed as a fixed dollar amount or a percentage of cost (3–8% is common on commercial GMP work, varying by market and project risk). Unlike in a lump sum contract, the GC fee in a GMP contract is typically negotiated openly.
Contingency
A critical and often contested component. The GMP typically includes two layers of contingency:
- GC Contingency: Owned by the GC to cover cost growth on buyout, scope gaps, productivity shortfalls, and subcontractor performance issues. Typically 2–5% of construction cost.
- Owner's Contingency: Held by the owner to fund scope additions, design changes, and unforeseen conditions. Typically 5–10% of construction cost.
Who controls which contingency is a fundamental negotiating point in GMP contracts. Owners typically want to control both; GCs need to negotiate adequate contractor contingency to protect themselves from normal execution risk.
Allowances
For items where pricing is not yet definable at GMP establishment — specific finishes, owner-furnished equipment, utility fees — an allowance is inserted as a placeholder. The actual cost replaces the allowance as the project progresses. Allowance reconciliation is tracked throughout the project and settled at final accounting.
Savings Sharing
If the project completes under the GMP, the savings are shared per a formula agreed in the contract. A common structure is 50/50 or 70/30 (owner/GC). This provision aligns the GC's financial interest with the owner's desire for cost efficiency — the GC earns more by buying out subs well and executing efficiently. (Source: AIA Contract Documents, "Guaranteed Maximum Price Contracts: A Complete Guide" — https://learn.aiacontracts.com/articles/understanding-guaranteed-maximum-price-contracts/)
HOW THE GMP IS SET: THE PRECONSTRUCTION PROCESS
The GMP doesn't appear out of thin air. It is the product of a preconstruction process in which the GC develops progressively more detailed estimates as design advances, aligning cost with the owner's budget before a maximum price is committed.
Conceptual Budget (Schematic Design Phase)
At SD, the GC provides an order-of-magnitude cost range — typically using square foot benchmarks by building type and region. This tells the owner whether the program is fundable and whether design decisions are pushing cost above the budget ceiling.
Design Development Estimate
As design matures, the GC refines the estimate using quantity takeoffs from DD drawings and subcontractor budget pricing on major scopes. This is the critical alignment milestone: if the design development cost exceeds the owner's budget, scope or design must be adjusted before construction documents are completed.
GMP Proposal
At 60–90% construction documents, the GC issues the formal GMP proposal. This includes the defined scope, subcontract buyout plan, allowances for incomplete design elements, contingency amounts, the fee, and the maximum price. How to Build a GMP Proposal Package covers exactly what goes in a GMP proposal document.
The quality of the subcontractor bid leveling process at this stage directly determines how reliable the GMP is. When the GC solicits sub bids to build the GMP, each trade's proposals need to be normalized — scope gaps between subs identified, exclusions quantified, and the total cost modeled accurately. AI bid leveling tools like Melt Bid (https://www.meltplan.com/bid) read sub proposals and flag scope gaps automatically, helping GCs establish a GMP they can hold rather than a number built on incomplete bid comparisons.
For a full breakdown of how the estimation process underpins the GMP, see How to Estimate Construction Costs.
RISKS FOR THE GC IN A GMP CONTRACT
GMP contracts shift meaningful cost risk to the GC. Understanding where that risk concentrates is essential before signing.
Scope Definition Risk
If the GMP is set before design is complete, gaps in the drawings become gaps in the estimate — which become the GC's problem if they exceed the contingency. Well-structured GMP contracts tie the GMP to a specific set of drawings and specifications; scope additions above that baseline are change orders at the owner's cost.
Buyout Risk
Even with a solid estimate, the GC doesn't know the true cost of subcontracted work until buyout is complete. If subcontractors come in over the budgeted amounts — due to market escalation, scope growth, or bid coverage gaps — the GC absorbs the difference from contingency. This is why thorough bid leveling before GMP establishment matters: the closer the budgeted sub amounts are to actual market pricing, the less buyout risk the GC carries.
Subcontractor Performance Risk
A sub who goes bankrupt, abandons work, or fails to perform is the GC's problem in a GMP contract. The cost to re-bid the scope, mobilize a replacement, and recover schedule comes out of GC contingency. Strong prequalification of subcontractors reduces this risk materially. Construction Buyout covers how the buyout process connects to GMP risk management.
Escalation Risk
On projects with long construction schedules or significant procurement lead times, material price escalation between GMP establishment and procurement can exceed contingency. Structural steel, MEP equipment, and electrical gear are particularly exposed to 2026 tariff volatility. GCs bidding GMP work should include escalation contingency as an explicit line item or negotiate an escalation clause into the contract.
BENEFITS OF GMP CONTRACTS FOR GCS
While GMP contracts concentrate risk on the GC, they offer significant advantages:
Early engagement: GCs are brought in during preconstruction, building relationships before the project is competitively bid and positioning themselves as the builder for the subsequent phases.
Negotiated fee: Rather than competing purely on price against unknown competitors, the GC negotiates fee and general conditions openly with an owner who selected them on qualifications.
Savings opportunity: The cost savings provision gives the GC a direct financial incentive to drive efficient buyout — a lever that doesn't exist in lump sum work.
Collaborative dynamic: GMP contracts tend to produce more owner-contractor collaboration on scope, value engineering, and schedule than adversarial lump sum bid environments.
FREQUENTLY ASKED QUESTIONS
What happens if a GMP project goes over budget?
If actual costs exceed the GMP — and the overrun is caused by work within the original scope — the GC is responsible for covering the difference out of their own fee or at a loss. The owner is protected by the maximum price ceiling. If the overrun is caused by owner-directed scope changes, design errors, or unforeseen conditions beyond the GC's control, a change order adds to the GMP.
Is a GMP contract the same as cost-plus?
A GMP contract is a type of cost-plus contract — the GC is reimbursed for actual costs plus a fee — but with a cost ceiling. A pure cost-plus contract has no cap; the owner pays actual costs plus fee regardless of the total. The GMP adds the maximum price protection that makes cost-plus viable for most private owners.
What is a good GC contingency amount in a GMP?
GC contingency typically ranges from 2–5% of construction cost, depending on design completeness at GMP establishment and project complexity. The less complete the design, the more contingency the GC needs to protect against scope gaps. Owners sometimes push for less contingency; GCs who accept thin contingency on incomplete designs frequently lose money on GMP projects.
How is a GMP different from a not-to-exceed contract?
They are effectively the same structure. Not-to-exceed (NTE) is an alternative label for the same mechanism: the GC cannot bill beyond the stated maximum without owner approval of a change order. GMP is the AIA contract terminology; NTE is common in smaller commercial and federal contracting contexts.
When should an owner NOT use a GMP contract?
When drawings are complete. If 100% construction documents exist and the project is competitively bid, a lump sum contract is appropriate — it eliminates open-book accounting complexity and gives the owner a true fixed-price commitment. GMP is most valuable when the owner wants to start construction before design is fully complete or wants the GC's cost input during design.
CONCLUSION
A GMP contract is the bridge between early contractor involvement and cost certainty. It allows owners to start building before every detail is resolved, while giving them the financial protection of a price ceiling. For GCs, it offers the advantage of early engagement and negotiated work — but demands rigorous preconstruction, accurate estimating, and thorough bid leveling to establish a GMP they can hold.
The reliability of a GMP is only as good as the estimate behind it. GCs who invest in thorough subcontractor bid coverage, careful scope normalization, and realistic contingency are the ones who close GMP projects under the maximum price and collect their share of the savings.
REFERENCES
1. AIA Contract Documents. "Guaranteed Maximum Price Contracts: A Complete Guide." https://learn.aiacontracts.com/articles/understanding-guaranteed-maximum-price-contracts/
2. AIA Contract Documents. "GMP in Construction Contracts: A Comprehensive Guide." https://learn.aiacontracts.com/articles/guaranteed-maximum-price-gmp-contracts-in-construction-a-comprehensive-guide/
3. Procore. "Guide to Guaranteed Maximum Price (GMP) Contracts in Construction." https://www.procore.com/library/gmp-contracts-construction
4. Autodesk. "Navigating Guaranteed Maximum Price (GMP) Contracts in Construction." https://www.autodesk.com/blogs/construction/guaranteed-maximum-price-gmp-contracts-construction/
5. Sage. "A guide to Guaranteed Maximum Price (GMP) contracts." https://www.sage.com/en-us/blog/gmp-contract-construction/
6. NetSuite. "How Do Guaranteed Maximum Price (GMP) Contracts Work?" https://www.netsuite.com/portal/resource/articles/accounting/guaranteed-maximum-price-contract.shtml
7. Document Crunch. "GMP in Construction: Meaning, Benefits & Contract Types." https://www.documentcrunch.com/blog/gmp-construction-contract
8. Master Estimators. "Guide to Guaranteed Maximum Price (GMP) Contracts in Construction." https://masterestimators.com/blog/guaranteed-maximum-price-gmp-contracts/