Types of Construction Contracts: A Practical Guide for Firm Leaders

The 7 Types of Construction Contracts at a Glance

The seven primary types of construction contracts are lump sum (fixed price), cost-plus, time and materials (T&M), unit price, guaranteed maximum price (GMP), design-build, and integrated project delivery (IPD). Incentive clauses can overlay several of these types to align performance goals. Each type allocates risk differently between owner and contractor.

The American Institute of Architects (AIA)¹ publishes standard forms for the most common types. The table below maps each contract type to its risk profile, best use case, and corresponding AIA form.

The risk spectrum runs from low contractor risk (T&M, cost-plus) through medium (unit price, GMP) to highest contractor risk (lump sum). Understanding where each type falls on that spectrum is the starting point for selection.

Now let's look at each type in detail— starting with the most common.

Lump Sum (Fixed Price) Contracts

In a lump sum contract, the contractor agrees to complete the project for a predetermined fixed price and bears all cost overrun risk. The owner gets budget certainty. The contractor keeps any savings. It's the most familiar contract type in construction— but familiarity doesn't make it the right choice for every project.

According to the AIA¹, the standard form for lump sum agreements is A101-2017. The structure is straightforward: a fixed price for a defined scope, with the contractor absorbing any cost overruns. In a lump sum contract, the contractor retains savings below the fixed price²— a critical distinction from GMP contracts, where savings go to the owner.

When lump sum works well:

• Scope is 95%+ defined with complete drawings
• Competitive bidding is the priority
• Owner wants maximum budget certainty
• Project is straightforward with low change likelihood

When to avoid lump sum:

• Scope is still evolving or design is incomplete
• Project conditions are uncertain (renovation, site unknowns)
• High probability of change orders— each one becomes a negotiation

Cash flow is the simplest under lump sum. Billing follows milestone-based draws, and the accounting is clean. But that simplicity comes at a price: the contractor is incentivized to cut corners when margins get tight. And every change order becomes a conversation about money.

When scope isn't fully defined, cost-plus contracts shift the risk equation.

Cost-Plus Contracts and Variations

Cost-plus contracts reimburse the contractor for actual project costs plus a fee, shifting most financial risk to the owner. The three common variations— fixed percentage, fixed fee, and fixed fee with guaranteed maximum price— offer progressively more cost control.

The AIA's A102-2017¹ covers cost-plus contracts with or without a GMP cap. Here's how the three variations compare:

Cost-plus is the right structure when scope is genuinely uncertain. Renovation work, evolving designs, and projects where the owner prioritizes quality over a fixed price tag all fit here. The tradeoff is real: documentation-intensive billing can delay payments compared to lump sum, and the owner bears the cost risk unless a GMP cap is applied.

One detail that matters for your accounting team: billing on cost-plus contracts follows actual cost incurrence, not the milestone-based draws common with lump sum. In practical terms, cash flow is less predictable— your CFO will want to plan for that difference.

The important thing to remember is that cost-plus isn't one contract type— it's three. And the GMP variation behaves differently enough to deserve its own close look.

Guaranteed Maximum Price (GMP) Contracts

A GMP contract sets a cost ceiling where the contractor absorbs any costs above the maximum price³. The owner retains savings below the cap. That single difference from lump sum— where the contractor keeps savings— changes how both parties approach the project.

GMP is technically a cost-plus variant, but it behaves differently in practice. Open-book accounting means the owner sees actual costs in real time. That transparency builds trust. And because the contractor absorbs overruns above the cap, there's a built-in incentive to manage costs efficiently.

This isn't a niche structure. According to DBM Team's analysis⁴, the Top 400 largest general contractors use construction manager at risk (CMAR)— which typically includes a GMP component— on 36% of their projects. The Top 25 use it on 47%.

Key advantages for owners:

• Budget certainty with a hard cap
• Visibility into actual costs (open-book)
• Savings below the cap stay with the owner
• Some GMP contracts include shared savings clauses as an incentive

Key advantages for contractors:

• Less competitive bidding pressure than lump sum
• Collaborative relationship with owner
• Shared savings clauses reward efficient execution

GMP works best for large projects where scope is mostly defined but not 100% complete. The owner gets a budget ceiling with flexibility underneath it.

For smaller tasks or emergency work, T&M and unit price contracts offer different trade-offs.

Time & Materials (T&M) and Unit Price Contracts

Time & Materials (T&M)

Time and materials contracts pay for actual labor hours plus materials at agreed rates, making them ideal for work where scope is genuinely unknown. T&M is the go-to for emergency repairs, investigations, and exploratory work— situations where defining scope upfront would cost more than the work itself.

The structure is simple. Labor hours multiplied by agreed rates, plus materials cost with typically a 10–30% markup³. The owner bears most of the risk unless a "not-to-exceed" clause is included, which effectively converts it to a capped T&M.

T&M is best for:

• Emergency repairs and disaster response
• Investigation and assessment work (what's behind that wall?)
• Small tasks where formal bidding costs more than the work
• Pre-construction services and feasibility studies

Cash flow moves fast under T&M. Billing cycles are short and the documentation burden is lighter than cost-plus. And disputes are rare— when rates are agreed upfront, there's less to argue about.

Unit Price Contracts

Unit price contracts pay a fixed rate per measured unit of work— cubic yards of concrete, linear feet of pipe, tons of asphalt. The risk is split: the owner bears quantity risk (how many units are needed), while the contractor bears per-unit cost risk.

This structure dominates civil and infrastructure work. Highway paving at a fixed rate per lane-mile. Utility installation priced per linear foot. The risk is shared proportionally⁵: actual quantities may differ from estimates, but the rate per unit holds firm.

Billing is based on field measurements, which means quantity surveyors play a critical role. Unit price contracts are straightforward in concept— but underestimating quantities can turn a profitable project into a loss, while overestimating inflates the bid and costs you the job.

For projects where speed and single-point accountability matter, design-build and IPD take a fundamentally different approach.

Design-Build and Integrated Project Delivery (IPD)

Design-Build

Design-build contracts place design and construction under a single entity, eliminating the traditional separation between architect and contractor. The owner deals with one team, one contract, one point of accountability. And the market is moving in this direction— fast.

According to DBIA's 2025 Data Sourcebook⁶, a joint study with FMI Corporation⁷, design-build is projected to account for nearly 50% of all U.S. construction spending by 2028. The performance data explains why: design-build projects are delivered 102% faster⁶ than traditional design-bid-build, with 3.8% less cost growth⁶. That's a $2.6 trillion bet the industry is making on single-entity delivery.

Meanwhile, design-bid-build's share is falling to roughly 15%⁷ of construction spending. The AIA standard form for design-build is A142-2014¹.

Design-build works best for fast-track projects, overlapping design and build phases, and owners who want a single point of accountability.

Integrated Project Delivery (IPD)

IPD goes further. It brings the owner, designer, and contractor into a single multi-party agreement with shared risk and shared reward. The AIA standard form is A195-2008¹.

The results are compelling. HDR completed approximately 32 IPD projects over seven years, achieving cost savings of roughly 12.8%⁸. And according to DocumentCrunch⁵, IPD projects report a success rate exceeding 98% against established performance measures.

But IPD requires something most contract types don't: genuine trust between all parties before the project begins. The Lean Construction Institute⁹ identifies three prerequisites— owner commitment, team buy-in, and Lean training.

Beyond these seven core types, incentive contracts add a performance layer that can improve outcomes under any structure.

Incentive Contracts: The Performance Overlay

Incentive contracts aren't a standalone type. They layer onto GMP, cost-plus, or T&M contracts to align financial rewards with performance targets— schedule bonuses, shared savings, quality milestones. Done right, they're the closest thing construction has to a win-win clause.

DocumentCrunch⁵ categorizes incentive clauses as an overlay mechanism rather than a separate contract family. Mastt's analysis¹⁰ identifies several common structures:

• Fixed-price incentive (FPIF): Shared savings/overruns against a target cost
• Cost-plus incentive (CPIF): Fee adjusts based on actual vs. target cost
• Schedule-based: Bonuses for early completion, penalties for delays
• Performance-based: Tied to quality metrics, safety records, or sustainability targets

Incentive contracts work best for complex infrastructure, time-sensitive projects, and renovation work where innovation or creative problem-solving adds value. A GMP contract with a 50/50 shared savings clause below the cap is one of the most common examples.

Knowing the options is step one. The harder question: how do you choose?

How to Choose the Right Contract Type

Choose a construction contract type based on five factors: how well-defined your scope is, how much budget certainty you need, your risk tolerance, your timeline urgency, and the trust level between owner and contractor. This five-factor framework— drawn from Mastt's selection methodology¹¹— gives you a repeatable decision process rather than gut instinct.

Here's a scenario. You're a $15M general contractor bidding on a hospital expansion with 80% design completion and a tight timeline. The scope is mostly defined but not fully locked. Fast-track matters. Design-build with a GMP cap likely fits— combining speed with cost protection for the owner.

But change the variables. If that same project has 100% drawings and three competing contractors, lump sum makes more sense. If it's a renovation with unknowns behind every wall, cost-plus gives you the flexibility to handle what you find.

Contract type shapes behavior. It doesn't replace good relationships, clear communication, or competent project management. Both are true. The contract sets the structure— the people make it work.

As your firm takes on more diverse project types, the full spectrum of contract options becomes a strategic toolkit— worth exploring before the next bid lands on your desk.

Change orders are where contract type theory meets project reality.

How Change Orders Work Under Different Contracts

Change order risk varies dramatically by contract type. In a lump sum contract, every change order adds cost on top of the fixed price. In cost-plus, changes are absorbed into actual costs. In GMP, changes erode the owner's savings cushion.

The stakes are real. 35% of construction projects face at least one major change during execution¹². And scope creep accounts for nearly 80% of cost overruns¹²— making the contract's change order provisions one of the most consequential clauses in the agreement.

The AIA defines a change order¹³ as a written instrument signed by the owner, contractor, and architect. Change orders typically fall into four categories¹⁴: lump sum, zero cost, T&M, and unitary cost.

Here's how change orders play out under each contract type:

The contract type you choose determines how painful changes will be. If you're expecting a clean, change-free project, any type works. If changes are likely— and they usually are— your contract type needs to account for that reality.

Construction contracting is also shifting. A few recent trends are worth tracking.

Key Trends: Standard Forms, Regulatory Changes, and AI Tools

Three trends are reshaping construction contracting in 2026: the evolution of standard forms from AIA and ConsensusDocs, new state-level legislation affecting contract terms, and AI tools that are cutting contract review time in half.

Standard Forms: AIA vs. ConsensusDocs

The AIA produces over 200 contract templates¹ used throughout the construction industry. But they're not the only option. ConsensusDocs, endorsed by 40+ organizations including the AGC¹⁵, offers an alternative that many contractors consider more balanced between owner and contractor interests.

Knowing which standard form to start from matters. AIA contracts lean slightly owner-favorable. ConsensusDocs aim for a more neutral starting point. Your attorney should advise— but understanding the difference gives you better leverage in negotiations.

Regulatory Shifts

State legislatures are tightening contract provisions. One example: New York's Prompt Payment Act amendment, effective December 19, 2025¹⁶, makes retainage provisions exceeding 5% void and unenforceable in private construction contracts. That's a significant shift for firms operating in New York.

The signal is clear. Regulatory environments are evolving, and standard contract templates may not reflect current law. Check your jurisdiction before relying on any boilerplate.

AI Tools for Contract Review

AI tools can now reduce construction contract review time by 50% or more¹⁷— flagging risky clauses, missing terms, and non-standard language that human reviewers might miss under deadline pressure. Several platforms focus specifically on construction:

• [Document Crunch](https://www.documentcrunch.com/blog/how-to-use-ai-for-contract-management): Construction-specific AI risk analysis across AIA and ConsensusDocs standards¹⁸
• Mastt: AI construction contract review starting at $150/month per project
• [LegalOn](https://www.legalon.ai/): Supports AIA and ConsensusDocs template comparison
• Spellbook: Pattern recognition across similar agreements

Here's what these tools actually do well: clause extraction, risk assessment, and detecting non-standard language. They're excellent at the first pass. What they can't do is negotiate, interpret jurisdiction-specific nuance, or make the strategic judgment calls that experienced attorneys handle.

AI augments expertise here. It doesn't replace it. The firms that use these tools effectively pair them with human review— letting AI handle the volume work so attorneys can focus on the judgment calls. That's the kind of workflow where an AI implementation partner can help construction firms move faster without cutting corners.

If you're exploring how AI fits into your broader operations, the best AI tools for business extend well beyond contract review.

Conclusion

Contract selection is a strategic decision that shapes risk allocation, cash flow, change order exposure, and project outcomes. The firms that get this right don't just know the definitions— they match the contract type to the specific realities of each project.

Most firms default to one or two contract types out of habit. That's understandable. But in a $2.2 trillion U.S. construction market¹⁹, the difference between the right contract type and the familiar one can mean millions in unnecessary risk exposure.

Use the five-factor framework: scope definition, budget certainty, risk tolerance, timeline urgency, and the relationship between parties. Evaluate contract type on a project-by-project basis. And consult your construction attorney before finalizing any contract structure— this guide informs your strategy, but it doesn't replace legal counsel.

If navigating contract decisions alongside AI automation and operational efficiency feels like a lot to manage, you're not wrong. Dan Cumberland Labs helps construction firms integrate AI tools into workflows like contract management, scheduling, and project delivery— so you can focus on building.

For firms exploring where AI fits into broader operations, the AI decision framework for founders is a practical next step.

Frequently Asked Questions

What is the most common type of construction contract?

Lump sum (fixed price) contracts are the most widely used, particularly for projects with well-defined scopes. The contractor agrees to a fixed price and bears all cost overrun risk, while the owner gets maximum budget certainty. The AIA A101-2017¹ is the standard form.

What is the difference between lump sum and GMP?

The key difference is who keeps the savings. In a lump sum contract, the contractor retains any savings below the fixed price. In a GMP contract, the owner retains savings below the cost ceiling.² That single distinction changes how both parties approach cost management throughout the project.

What is a cost-plus contract in construction?

A cost-plus contract reimburses the contractor for actual project costs plus a fee¹. The fee can be structured as a fixed percentage of costs, a flat dollar amount, or a fixed fee with a guaranteed maximum price cap. It's best for projects where scope is uncertain or evolving.

When should you use a time and materials contract?

T&M contracts are best for work where scope is genuinely unknown— emergency repairs, investigation and assessment work, or small tasks where defining scope upfront would cost more than the work itself³. Always consider adding a not-to-exceed clause to limit the owner's exposure.

What is integrated project delivery (IPD)?

IPD is a multi-party contract where the owner, designer, and contractor share both risk and reward through a single integrated agreement⁹. It requires established trust between all parties and is best suited for complex projects like hospitals and research facilities. The AIA A195-2008¹ is the standard form.

References

1. 1. learn.aiacontracts.com
2. 2. hansen-rice.com
3. 3. procore.com
4. 4. dbmteam.com
5. 5. documentcrunch.com
6. 6. dbia.org
7. 7. fmicorp.com
8. 8. hdrinc.com
9. 9. leanconstruction.org
10. 10. mastt.com
11. 11. mastt.com
12. 12. k38consulting.com
13. 13. learn.aiacontracts.com
14. 14. billd.com
15. 15. agc.org
16. 16. andersonkill.com
17. 17. spellbook.legal
18. 18. mastt.com
19. 19. fmicorp.com