How to Understand a GMP Contract in Construction

A Guaranteed Maximum Price contract sounds like exactly what it promises: a ceiling on what you will pay. In practice, the guarantee is only as strong as the language that defines it. Jacksonville hospital construction and large commercial projects run on GMP contracts. So do the deals where owners find themselves paying more than the "maximum" because the contingency language was loose and the GC knew how to use it.

This guide breaks down what a GMP contract actually contains, how the money flows, and when you should walk away from GMP in favor of a fixed-price arrangement.

Step 1: Define GMP vs. Fixed-Price vs. Cost-Plus

These three contract types put cost risk in different places.

Fixed-price (lump sum): The GC commits to a specific price for a specific scope. If the work costs more than expected, the GC absorbs it. If it costs less, the GC keeps the savings. Risk sits with the contractor.

Cost-plus: The owner pays actual cost of construction plus a fee (percentage or fixed). The GC has no incentive to control costs, and the owner carries all cost risk. Rarely appropriate for owners who are not also acting as their own construction manager.

Guaranteed Maximum Price (GMP): A hybrid. The GC establishes a cost ceiling. Below that ceiling, the owner pays actual costs plus a fee. If costs exceed the GMP, the GC absorbs the overage -- in theory. In practice, the contingency provisions and change order rights often allow the GC to raise the GMP before the project is complete.

Pro tip: When a GC proposes GMP on a project where the design is already fully complete, push back. GMP is appropriate when design is incomplete and scope is genuinely uncertain. On a fully designed project, there is no reason the GC cannot offer a fixed-price contract.

Step 2: Understand the Four Sections of a GMP Contract

Every GMP contract has four core components. Know what each one means before you sign.

1. Fee: The GC's profit. Typically 3% to 8% of cost of work on large commercial projects, depending on project complexity and risk. This is non-negotiable once work starts, so negotiate it at award.

2. General Conditions: The GC's cost of managing the project: superintendent salary, project manager time, site trailer, temporary utilities, insurance, bond premium. General conditions are often where GCs bury cost without scrutiny. A vague general conditions budget is a red flag.

3. Estimated Cost of Work: The direct cost of labor, materials, and subcontractors. This is the main variable. On a GMP, the GC estimates this based on available design documents and carries contingency to cover gaps.

4. Contingency: A reserve for cost uncertainty. This is the most negotiated and most misunderstood section of a GMP contract.

Warning: A GMP with general conditions described only as a lump sum rather than a detailed line-item budget gives the GC enormous flexibility to shift costs. Require an itemized general conditions budget before signing.

Step 3: How Contingency Pools Work

Most GMP contracts have two contingency pools. Understanding who controls each pool determines how much of the "maximum" is actually guaranteed.

GC Contingency: Controlled by the GC. Used to cover cost growth within the GC's original scope -- estimating errors, subcontractor buyout savings that get spent elsewhere, efficiency losses. The GC can draw on this without owner approval. At the end of the project, GC contingency savings are typically split according to a negotiated sharing ratio (see Step 5).

Owner Contingency: Controlled by the owner. Used for scope changes, design development changes, and owner-directed additions. The GC cannot draw on owner contingency without written owner authorization.

Pro tip: Negotiate a hard cap on GC contingency as a percentage of the cost of work (typically 3% to 5%). A GC contingency of 10% on a $10 million project is $1 million of money that the GC can spend with limited accountability.

Step 4: What "Open-Book" Means in Practice

GMP contracts are typically described as "open-book," meaning the GC shares actual cost data with the owner. In practice, open-book ranges from genuinely transparent to technically compliant but useless.

Genuine open-book access means:

• Monthly cost reports showing actual costs against the GMP line by line
• Copies of all subcontractor invoices and pay applications
• GC's buyout log showing where subcontract awards came in above or below the GMP estimate
• Real-time access to job cost reports (some GCs provide owner access to Procore or CMiC)

Technical compliance looks like:

• A summary-level report that shows you the total spent vs. total GMP but no line-item detail
• Invoices available "upon request" but not proactively shared
• Buyout savings rolled into GC contingency rather than returned to the owner's cost of work

Warning: If your GMP contract does not specify the format and frequency of cost reporting in the contract documents themselves, it will default to whatever level of detail the GC finds convenient.

Step 5: How Savings Are Shared

If the project comes in under the GMP, the savings sharing provision determines who keeps the difference between the GMP ceiling and actual cost. This is one of the most negotiated provisions in a GMP contract.

Common structures:

• GC keeps all savings: Effectively turns the GMP into a lump sum. Rare, and bad for owners.
• 50/50 split: Owner and GC share savings equally. Standard on many commercial projects.
• 75/25 or 80/20 (owner/GC): Owner-favorable. Appropriate when the design is mature and GC cost risk is low.

Pro tip: Savings sharing is most meaningful when the GMP is set early and scope is well-defined. A GMP set with incomplete design documents and then supplemented by dozens of change orders as design develops leaves little room for savings.

Step 6: When GMP Is Appropriate vs. Fixed-Price

GMP is appropriate when:

• Design is 30% to 60% complete (schematic or design development phase)
• The owner wants to start construction before design is complete (fast-track delivery)
• The project has genuine scope uncertainty (adaptive reuse, historic renovation, healthcare construction with complex infection control requirements)
• The owner has the internal capacity to manage an open-book contract (or has hired an owner's representative)

Fixed-price is appropriate when:

• Design is 90%+ complete with fully coordinated construction documents
• The scope is well-defined and repeatable (tenant fit-out, ground-up warehouse, residential addition)
• The owner does not have the capacity to manage ongoing cost reporting and GMP auditing
• The owner wants certainty over flexibility

In Jacksonville, GMP is standard for hospital construction and large institutional projects where the design team and GC overlap during the pre-construction phase. For ground-up commercial construction with complete documents, JK Prestige Construction delivers fixed-price contracts that put the cost risk where it belongs -- with the contractor.

Step 7: Red Flags in a GMP Contract

Before signing a GMP contract, check for these specific problems:

High contingency with vague definition: A GMP contingency above 5% of cost of work without a detailed breakdown of what it covers is a sign the GC is padding the maximum price.

Vague general conditions: If the general conditions section is a single lump sum rather than an itemized budget, negotiate a line-item breakdown before signing. Superintendent cost alone should be a discrete line.

Broad change order rights: Some GMP contracts allow the GC to increase the GMP for "design development changes" even when no scope has been added. Define exactly what triggers a GMP amendment.

No savings sharing provision: If the contract is silent on what happens when the project comes in under the GMP, the GC keeps everything. Do not let this go unaddressed.

GC contingency controlled jointly: Some contracts give the GC contingency to the GC but require owner notification rather than owner approval before drawdown. That is better than nothing but still leaves you reacting rather than approving.

Pro tip: Have a construction attorney review any GMP contract above $500,000 before signing. The fee is small relative to the exposure. For commercial projects in Jacksonville, this is standard practice for sophisticated owners.

Step 8: What to Audit Quarterly on a GMP Project

Once a GMP project is underway, set a quarterly audit cadence. Review the following:

• Subcontractor buyout log: Every subcontract that was awarded below the GMP estimate represents savings. Confirm those savings are reflected in the GMP cost tracking.
• GC contingency drawdown log: Who approved each draw? What was it used for? Does the use align with the contract definition of GC contingency?
• Change order log: Every GMP amendment should be documented with a scope description, cost justification, and schedule impact. Verify that amendments are genuinely scope additions, not GC contingency exhaustion dressed up as scope changes.
• General conditions actual vs. budget: Are superintendent hours tracking to the budget? Is the GC billing for general conditions staff who are also billing to other projects?

At JK Prestige Construction, fixed-price contracts eliminate most of this audit burden by putting cost risk with the contractor from day one. For projects where GMP is the appropriate delivery method, the same transparency principles apply.

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