What are the six most common construction contracts?

The six most common construction contracts are lump sum, cost-plus, time and materials, unit price, guaranteed maximum price (GMP), and design-build. Each structure defines how pricing, risk, and responsibility are allocated between parties, directly impacting project cost control, flexibility, and legal exposure.

Why Contract Type Matters

Construction contracts do more than define payment—they define risk, control, and outcomes.

Choosing the wrong structure can lead to:

  • cost overruns
  • disputes over scope
  • delayed timelines
  • inconsistent enforcement of terms

For legal and procurement teams, you must understand these contract types and ensure they are applied consistently across projects.

This is where structured contract automation platforms like BlackBoiler become critical, enabling organizations to enforce preferred contract positions at scale.

Contract TypePricing StructureRisk AllocationBest Use Case
Lump SumFixed total priceContractor assumes riskClearly defined scope
Cost-PlusCost + feeOwner assumes more riskEvolving scope
Time & MaterialsHourly + materialsShared riskUndefined or ongoing work
Unit PricePer unit pricingModerate/sharedRepetitive tasks
Guaranteed Maximum Price (GMP)Cost with capBalanced riskLarge, complex builds
Design-BuildIntegrated deliveryContractor assumes more controlSpeed and efficiency
 

The 6 Types of Construction Contracts 

 
A fixed-price agreement where the contractor agrees to complete the project for a set amount.
Learn more:/contract-definitions/lump-sum-contract
 
The contractor is reimbursed for actual costs plus an agreed-upon fee or percentage.
Learn more: /contract-definitions/cost-plus-contract
 
Payment is based on labor hours and materials used.
Learn more:/contract-definitions/time-and-materials-contract
 
Costs are calculated based on predefined unit rates (e.g., per square foot, per mile).
Learn more:/contract-definitions/unit-price-contract
 
A cost-plus contract with a ceiling that limits the total project cost.
Learn more:/contract-definitions/guaranteed-maximum-price
 
A single entity handles both design and construction, streamlining delivery.
Learn more:/contract-definitions/design-build-contract
 

How Risk Shifts Across Contract Types 

One of the most important differences between these contracts is who carries the risk:
  • Owner-heavy risk: Cost-Plus, Time & Materials
  • Contractor-heavy risk: Lump Sum, Design-Build
  • Balanced risk: GMP, Unit Price
 
This allocation directly affects:
  • negotiation strategy
  • fallback clause selection
  • approval workflows
 

Why Contract Structure Alone Isn’t Enough

 
Even with the right contract type, organizations often struggle with:
  • inconsistent clause enforcement
  • deviation from approved legal positions
  • manual review bottlenecks
  • lack of institutional learning
 
Regardless of contract type, BlackBoiler addresses this by transforming contract playbooks into enforceable, repeatable automation, ensuring that every construction contract aligns with organizational standards.
 

Related Contract Definitions 

The lump sum contract is the most common construction contract, particularly for projects with clearly defined scope and requirements.

Cost-plus and time and materials contracts typically carry the most risk for owners because final costs are not fixed.

Lump sum and guaranteed maximum price (GMP) contracts provide more cost certainty and reduce financial risk for owners.

A GMP contract is a type of cost-plus contract with a maximum price cap, limiting the total cost exposure for the owner.

The six most common construction contracts are lump sum, cost-plus, time and materials, unit price, guaranteed maximum price (GMP), and design-build. Each structure defines how pricing, risk, and responsibility are allocated between parties, directly impacting project cost control, flexibility, and legal exposure.

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