Contracts

What is a guaranteed maximum price in construction?

A guaranteed maximum price (GMP) is a ceiling on what the owner will pay: the contractor is reimbursed its actual costs plus a fee, but the total cannot go above the agreed cap without a change order.

Two construction professionals review paper plans beside a tablet at a jobsite workbench.
Plan reviews connect field conditions, drawings, and the next decisions on a job. AI-generated illustration.

A guaranteed maximum price is the price cap in a cost-plus contract. The owner pays the contractor's actual cost of the work plus an agreed fee, up to a maximum. If costs come in under the cap, the owner keeps some or all of the savings, depending on the contract. If costs run over, the contractor generally absorbs the overrun, unless the overrun comes from a change in scope.

GMPs are common with construction management at risk and some design-build deals. This page covers the price itself; for the overall contract form, see GMP contract.

How a GMP gets set

The GMP is usually set before construction starts but after enough design exists to price it, often at design development or partway through construction documents. Under the AIA A133 owner and construction manager agreement, for example, the construction manager proposes a GMP, the owner can accept, reject, or negotiate it, and the GMP takes effect when the owner signs a GMP amendment.

A typical GMP proposal includes:

  • The estimated cost of the work, broken into a schedule of values.
  • The contractor's fee, often a percentage of cost or a fixed amount.
  • General conditions costs for running the site.
  • A contractor's contingency for scope that is in the design intent but not fully drawn.
  • Allowances, assumptions, clarifications, and exclusions that define what the GMP does and does not cover.

Worked example

A CM at risk signs a $6,000,000 GMP for a medical office building. The fee is 4 percent of cost, and the contract splits savings 50/50. At the end, the actual cost of the work plus fee totals $5,700,000.

Example: GMP close-out with shared savings
LineAmount
Guaranteed maximum price$6,000,000
Actual cost plus fee$5,700,000
Savings below GMP$300,000
Contractor share (50%)$150,000
Owner pays$5,850,000

If costs had come in at $6,250,000 instead, the owner would pay $6,000,000, and the contractor would eat $250,000, unless it could show a change in scope that justified a change order raising the GMP.

The A133 summary also points out that schedule of values lines are not separate guarantees. A single line can run over as long as the total GMP holds, and moving money out of contingency needs documentation to the architect.

Common disputes

  1. Scope vs design development: the owner calls a new detail "design development" covered by contingency; the contractor calls it a scope change.
  2. Non-reimbursable costs: contracts list costs the owner will not pay, such as certain bonuses or home-office staff. Billing them anyway leads to audit findings.
  3. Contingency use: owners often want approval before the contractor spends its contingency.
  4. Open books: most GMPs give the owner audit rights, so cost records must be clean. See open-book pricing.

Compare a GMP with a cost-plus contract without a cap and a lump sum contract. Smart Business Automator tracks cost of the work against the GMP and contingency in real time and routes changes for approval; see change order approval automation.

Frequently asked questions

Who keeps the savings under a GMP?

The contract decides. Some give all savings to the owner, others split them by a set ratio as an incentive for the contractor.

Can a GMP go up?

Yes, through approved change orders for added scope, owner-caused delays, or other events the contract treats as changes. Ordinary overruns do not raise it.

Is GMP the same as a lump sum?

No. A lump sum is a fixed price where the contractor keeps any savings. A GMP reimburses actual cost plus fee up to a cap, usually with open books.

When is the GMP set?

Usually once design is far enough along to price with confidence, often during design development or construction documents, and documented in a GMP amendment.

Sources

  1. AIA Contract Documents: Summary of A133-2019, Owner and Construction Manager as Constructor with a GMP
Written and edited by

Maurice Francois writes and edits construction operations guides for Smart Business Automator. More from Maurice on the Scaling Legends podcast.

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