Contract Types Used in Commercial Contracting

Commercial construction projects in the United States are governed by formal written agreements that define how risk, payment, and scope are allocated between owners, contractors, and subcontractors. The contract type selected for a given project shapes cost predictability, scheduling flexibility, and liability exposure across every phase of work. This page covers the primary contract structures used in commercial contracting, how each mechanism operates, the project scenarios where each type is most appropriate, and the decision boundaries that determine which structure fits a given engagement.

Definition and scope

A commercial construction contract is a legally binding agreement that establishes the terms under which a contractor performs construction services on a non-residential or mixed-use structure. These agreements are governed by a combination of state contract law, federal procurement rules (for government projects), and industry-standard documents published by organizations such as the American Institute of Architects (AIA) and the Engineers Joint Contract Documents Committee (EJCDC).

Contract type selection intersects directly with how a project is delivered. As covered in commercial contractor project delivery methods, the delivery method — design-bid-build, design-build, or construction management — constrains which contract structures are practically available. The five primary contract types in commercial contracting are:

  1. Lump Sum (Fixed Price)
  2. Cost Plus Fee
  3. Guaranteed Maximum Price (GMP)
  4. Unit Price
  5. Time and Materials (T&M)

Each type distributes financial risk differently between the owner and the contractor, and each requires a different level of pre-construction documentation to function as intended.

How it works

Lump Sum (Fixed Price): The contractor agrees to complete a defined scope of work for a single fixed amount. All cost overruns above that amount are absorbed by the contractor. This structure requires complete and accurate construction documents before bidding, because ambiguities in scope become the contractor's liability. AIA Document A101 is the most widely used standard form for lump sum agreements in commercial work (AIA A101-2017).

Cost Plus Fee: The owner reimburses the contractor for all allowable project costs — labor, materials, subcontractors, equipment — and pays an additional fee, either as a fixed amount or as a percentage of total costs. This structure shifts cost risk to the owner but provides transparency. The fee percentage in commercial projects typically ranges from rates that vary by region to rates that vary by region of total construction costs, depending on project complexity and contractor overhead structure.

Guaranteed Maximum Price (GMP): A Cost Plus contract with a ceiling. The contractor agrees that total project cost — reimbursable costs plus fee — will not exceed an agreed maximum. Cost savings below the GMP are either retained by the owner or shared between owner and contractor according to a negotiated split. The GMP structure is commonly paired with commercial construction management services, particularly when an owner needs early contractor involvement before design is complete.

Unit Price: The contractor establishes a fixed price per measurable unit of work — cubic yards of concrete, linear feet of conduit, square feet of flooring. The total contract value is determined by actual quantities installed. This approach is standard in civil and site work where final quantities cannot be known precisely at bid time.

Time and Materials (T&M): The owner pays actual labor hours at agreed billing rates plus actual material costs, often with a markup cap. T&M is used for change order work, emergency repairs, and tenant improvement scopes where defining a fixed price upfront is impractical. The commercial contractor change order process often defaults to T&M billing when scope additions arise mid-project.

Common scenarios

Ground-up office construction typically uses a Lump Sum contract when the design is rates that vary by region complete at the time of bidding, or a GMP when the owner wants to engage the contractor during design development to control costs and compress schedule.

Tenant improvement and retail build-out projects — covered in detail under commercial renovation and tenant improvement — frequently use GMP or T&M structures because the scope evolves as tenant requirements are refined. A retail chain building out 12 locations simultaneously may use a Unit Price schedule for repetitive elements such as storefront systems, flooring, or ceiling grid installation.

Industrial and manufacturing facilities with complex MEP systems often use Cost Plus contracts, where owner visibility into subcontractor bids and material procurement is a priority. Federal and publicly funded projects are frequently subject to competitive bidding requirements that mandate Lump Sum or Unit Price structures under statutes such as the Federal Acquisition Regulation (FAR, 48 CFR).

Healthcare and institutional projects commonly use GMP agreements negotiated during schematic design, giving the owner a cost ceiling while preserving the ability to refine clinical layouts and equipment specifications during design development.

Decision boundaries

Selecting the appropriate contract type requires evaluating four criteria:

  1. Design completeness at contract execution — Lump Sum contracts require near-complete documents. Cost Plus and GMP contracts function with partial design.
  2. Owner's risk tolerance — Lump Sum transfers cost risk to the contractor. Cost Plus retains it with the owner.
  3. Project duration and change likelihood — Long, complex projects with evolving scope favor GMP or Cost Plus; straightforward, well-documented projects favor Lump Sum.
  4. Regulatory and procurement constraints — Public agency projects subject to competitive bidding laws generally require Lump Sum or Unit Price bids; sole-source negotiated contracts with GMP structures require specific statutory authority.

Lump Sum vs. GMP is the most consequential choice in commercial contracting. Lump Sum provides maximum price certainty but requires complete documents and eliminates transparency into contractor cost data. GMP provides a cost ceiling with transparency and allows earlier contractor engagement — but savings-sharing provisions and the definition of "allowable costs" must be negotiated carefully to avoid disputes. The commercial contractor bid process page outlines how these structures affect how bids are solicited and evaluated.

Payment structures — retainage percentages, schedule of values formatting, and pay application procedures — operate within whichever contract type is selected and are addressed separately under commercial contractor payment structures.

References

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