Contracts

What is a GMP contract in construction?

A GMP (guaranteed maximum price) contract reimburses the contractor's actual cost of the work plus a fee, but caps the owner's total at an agreed number. Costs above the cap are the contractor's problem.

A contractor and plan reviewer discuss drawings and permit paperwork across an office desk.
Keep plans, permit requirements and approvals together when preparing construction work. AI-generated illustration.

A GMP contract is a cost-plus contract with a ceiling. The owner pays the contractor's real, documented costs plus a fee, and the contractor guarantees that the total will not exceed the guaranteed maximum price. If the job comes in under, the owner usually keeps most or all of the savings. If it runs over, the contractor eats the difference unless the overrun comes from an approved change in scope.

Owners like it because they see the books and still get a cap. Contractors accept it because they are paid for real costs and are often brought in early, during design, when they can shape the budget.

How a GMP gets set

On most GMP jobs the contractor joins before drawings are finished. It provides preconstruction services, prices the design at each stage, and then submits a GMP proposal once documents are far enough along. The AIA's A133-2019 form, used with a construction manager as constructor, works this way: the construction manager submits a GMP proposal, the owner can accept, reject, or negotiate it, and once the owner signs the GMP amendment, the construction manager is bound to complete the work at or below that price. The AIA's A102-2017 is the owner and contractor version for cost of the work plus a fee with a GMP.

A GMP is built from layers: the estimated cost of the work, the contractor's contingency for buyout and coordination gaps, general conditions, insurance and bonds, and the fee. The assumptions and clarifications attached to the GMP matter as much as the number, because they define what the cap actually covers.

Worked example

Example GMP for a $6.2 million medical office building
ComponentAmount
Cost of the work (trades and self-perform)$5,300,000
Contractor contingency$210,000
General conditions$380,000
Insurance and bond$90,000
Fee$220,000
Guaranteed maximum price$6,200,000

Say final cost of the work lands at $5,150,000 and the contractor used $120,000 of contingency. Total cost plus fee comes in around $5,960,000, roughly $240,000 under the GMP. If the contract splits savings 75/25 in the owner's favor, the contractor picks up about $60,000 on top of its fee. If instead a curtain wall sub defaults and costs jump $400,000, the contractor burns its contingency and absorbs the rest, unless it can show a scope change.

Where GMP disputes start

  • What counts as cost of the work. Home office staff, equipment rates, and self-performed labor burden are common fights. Define them in the contract.
  • Contingency use. Owners want to approve every draw on contingency. Contractors want it for buyout busts and gaps. Write down who controls it.
  • Scope versus refinement. If drawings develop after the GMP is set, is that a change or just design completion? The clarifications list decides.
  • Audit rights. Owners can usually audit. Keep receipts, timesheets, and committed costs clean from day one.
  • Allowances. Reconcile every allowance against actual cost with a change order.

Related terms

GMP is the usual pricing model under construction management at risk and is common on design-build work. Compare it with a lump sum contract and a time and materials contract. On a GMP job, open-book job costing is not optional. Smart Business Automator keeps committed, actual, and forecast costs by cost code so the GMP position is visible every week; see job costing and WIP automation.

Frequently asked questions

Is a GMP contract the same as a fixed price contract?

No. A fixed price or lump sum contract pays one price no matter what the work costs. A GMP pays actual cost plus fee up to a cap, with open books, and savings below the cap often go back to the owner.

Who keeps the savings on a GMP contract?

Whatever the contract says. Some give all savings to the owner, others split them between owner and contractor at a set ratio. Negotiate it before the GMP is signed.

Can a GMP go up?

Yes, through approved change orders for added scope, owner-caused delays, or other events the contract allows. Cost overruns on the original scope do not raise it.

When is the GMP usually set?

Often during design development or construction documents, once the drawings are detailed enough to price with confidence. Setting it too early pushes risk into contingency and clarifications.

Sources

  1. AIA Contract Documents: Summary of A133-2019, Owner and Construction Manager as Constructor, Cost of the Work Plus a Fee 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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