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Cost Plus vs Fixed Price in Construction

Cost Plus vs Fixed Price in Construction

Starting a construction project requires choosing the right type of contract. A contract is a legal agreement between the project owner and the contractor that defines the project’s scope, timeline, and payment terms. The two common types are cost-plus and fixed-price contracts, each suitable for different situations.

The proper contract is crucial for project success, affecting cost control, flexibility, and final quality. A well-chosen contract ensures the project stays on budget, meets deadlines, and delivers desired results. Conversely, the wrong contract can lead to unexpected expenses, delays, and disputes.

Cost Plus vs Fixed Price Agreements

Cost-plus and fixed-price contracts are prevalent in construction. Cost-plus contracts pay the contractor for actual costs plus a fee, offering flexibility for changes in scope or design. While, fixed-price contracts set a price for the entire project upfront, providing cost certainty but less flexibility if changes are needed.

Let’s examine the details of what distinguishes cost-plus and fixed-price agreements and weigh the pros and cons of each.

What are Cost-Plus Contracts?

A cost-plus contract is an agreement in which the project owner pays the contractor for all actual project costs plus an additional fee. This type of contract is popular when the project scope isn’t fully defined, allowing for flexibility and adjustments as needed.


The two main elements of a cost-plus contract are the actual cost and the contractor’s fee.

Actual Cost

The actual cost includes all expenses related to the project. This can cover materials, labor, equipment, and any other fees that arise during construction. The project owner agrees to repay the contractor for these costs, covering all necessary expenditures.

Contractor’s Fee

In addition to the actual costs, the contractor earns a fee for their work. This fee can be fixed or a percentage of the total costs. The contractor’s fee compensates them for their time, effort, and expertise in project management.

Variations of Cost-Plus Contracts

There are different types of cost-plus contracts to fit various needs.

One variation is the cost-plus-fixed-fee contract. In this agreement, the contractor receives a fixed fee regardless of the project’s total cost. This setup clearly explains the contractor’s earnings from the start.

Another variation is the cost-plus percentage fee contract. Here, the contractor’s fee is a percentage of the total project costs. If the project costs increase, the contractor’s fee also increases. This type offers more incentive for the contractor to manage the project efficiently.

Benefits of Cost-Plus Contracts in Construction

Flexibility in Project Scope and Design Changes

Cost-plus contracts offer flexibility. Since the owner pays for all actual costs, they can change the project scope or design without renegotiating. This is useful when the final design still needs to be thoroughly planned. Owners can add features or change aspects without causing significant disruptions.

Lower Risk for Contractors

These contracts reduce financial risk for contractors. They get refunded for all actual costs, so they don’t have to worry about underestimating expenses. This extra payment verifies contractors won’t lose money if the project costs more than expected, allowing them to focus on quality without cutting corners.

Potential for Higher Quality Work

Cost-plus contracts can lead to higher-quality work. Contractors are compensated for actual costs and receive an additional fee, so they will likely use high-quality materials and skilled labor. There is no incentive to save money by choosing cheaper options, resulting in a better overall outcome.

Drawbacks of Cost-Plus Contracts in Construction

Less Cost Predictability for Buyers

Cost-plus contracts make it hard for buyers to predict the total project cost. The final amount depends on actual expenses, so setting a firm budget at the start is tough. If unexpected issues arise or the project scope changes, costs can quickly add up, causing stress for budget-conscious buyers.

Requires Detailed Tracking and Documentation

Contractors must keep accurate records of labor, materials, and other costs. This provides transparency and justifies expenses to the project owner but adds an administrative burden that can be time-consuming and complicated.

Potential for Higher Total Costs

Contractors, repaid for all expenses, have less incentive to keep costs down. They might choose higher-quality or more expensive options without budget concerns. While this can improve quality, it can also increase the overall project cost for the buyer.

What are Fixed-Price Contracts

A fixed-price contract is an agreement where the project owner and contractor agree on a set price for the entire project before work begins. The contractor completes the project for a lump sum payment, regardless of the actual costs during construction.

How DO They Work?

In a fixed-price contract, the project owner pays a predetermined amount for the entire project. This lump sum covers all costs, including materials, labor, and other expenses. The contractor manages these costs and completes the project within the agreed-upon budget.

If the project costs more than the lump sum, the contractor absorbs the extra fees. If it costs less, the contractor benefits from the savings.


It involves the lump sum payment, with variations to fit different project needs.

Firm Fixed Price

In a firm-fixed-price contract, the lump sum is set in stone. No matter what happens during the project, the contractor gets the agreed amount. This offers transparent cost predictability for the project owner.

Fixed Price with Incentive

The contractor can earn additional money to complete the project early or under budget. This encourages efficient work and cost control while providing high-quality outcomes.

Pros of Fixed-Price Contracts in Construction

Predictable Costs

The project owner and contractor agree on a set price before the project starts. This means the project owner knows exactly how much the project will cost, even if unexpected issues arise.

Simplified Billing

With one lump sum payment, there is less paperwork and fewer invoices to manage. This reduces confusion and makes it easier for both parties to track expenses.

Cost Control Incentives

Since contractors agree to a set price, they have a solid incentive to stay within budget. Suppose they complete the project for less than the agreed amount. In that case, they keep the savings, motivating efficient and top-level work.

Cons of Fixed-Price Contracts in Construction

Higher Risk for Contractors

Fixed-price contracts pose a higher risk for contractors. They must complete the project for a set price, covering unexpected costs. This can be financially risky, especially if unplanned issues arise.

Less Flexibility

The fixed price makes changes to the project scope or design difficult. Adding new features or modifying the design usually requires renegotiating the contract, which can delay the project and increase costs.

Potential for Lower Quality Work

Some contractors might cut corners to stay within budget, leading to lower-quality work. They may choose cheaper materials or rush the work to save money. This can result in a finished project that doesn’t meet the desired standards, compromising quality for cost control.

For understanding of How to do elemental cost analysis in construction.

Comparing Cost-Plus vs Fixed-Price Contracts

Cost Control and Predictability

Cost-plus and fixed-price contracts differ in cost control and predictability. In cost-plus contracts, the project owner covers all actual costs plus an additional fee, leading to less predictable final costs. Fixed-price contracts offer more predictable costs since the price is set from the start, making budgeting more accessible for the project owner.

Flexibility and Scope Changes

Flexibility is a crucial difference between these contracts. Cost-plus contracts allow more flexibility in scope and design changes without renegotiation. This is useful for evolving projects. Fixed-price contracts offer less flexibility, as changes usually require renegotiation, which can delay the project and add costs.

Risk Distribution Between Buyer and Contractor

Risk distribution varies between contracts. In cost-plus contracts, the project owner assumes more risk by covering all costs, which can lead to higher expenses if issues arise. Fixed-price contracts place more risk on the contractor, who must cover any unexpected costs. These contracts offer more cost certainty for the project owner but financial risk for the contractor.

Impact on Project Timeline and Quality

The contract type affects the project timeline and quality. Cost-plus contracts can lead to longer timelines due to flexibility for changes, potentially resulting in higher quality work since contractors aren’t pressured to cut corners. Fixed-price contracts, while offering cost control, can sometimes result in lower quality if contractors cut corners to stay within budget. They can also lead to faster completion as contractors are motivated to finish on time to avoid extra costs.

Decision Between Fixed Price and Cost Price for Construction Projects

Evaluation of the following factors is beneficial:

Risk Assessment

Start by assessing the likelihood of project scope changes. A cost-plus contract might be better if the design needs to be thoroughly planned or frequent changes are expected. This contract allows for adjustments without significant issues. If the scope is clear and unlikely to change, a fixed-price contract offers cost predictability and less risk of unexpected expenses.

Cost Control

Consider the level of cost control and transparency needed. Cost-plus contracts require detailed tracking of all expenses, providing transparency. If you need this level of monitoring and can manage the paperwork, a cost-plus contract works well. Fixed-price contracts simplify cost control with an agreed total price upfront, reducing the need for constant oversight.

Contractor’s Experience and Track Record

A contractor with a strong history of completing projects on time and within budget suits a fixed-price contract, handling financial risks effectively. If the contractor is known for managing complex projects with frequent changes, a cost-plus contract is more suitable, leveraging their experience with flexible project scopes.

Evaluating Project Requirements and Constraints

Start by evaluating your project requirements and constraints. Understand the project scope, timeline, and budget. A fixed-price contract might be best if the scope is clear and the budget tight. A cost-plus contract could be more suitable if the scope is flexible or uncertain. Consider any specific constraints like time limits or unique materials.

Consult with Construction and Legal Professionals

Seek advice from construction and legal professionals. Construction experts can explain the practical implications of each contract, while legal professionals ensure the terms protect your interests. Consulting with these experts can prevent problems and ensure smooth project execution.

Negotiating on Terms

Clearly define the project scope, payment terms, and responsibilities. If you have a low tolerance for financial risk, a fixed-price contract with clear cost limits might be best. If flexibility is more important, ensure your cost-plus contract allows for necessary changes without excessive costs. Negotiating favorable terms helps ensure the project runs smoothly and meets your expectations.


Choosing a suitable contract is crucial for a successful construction project. We explored cost-plus and fixed-price contracts, highlighting their benefits and weaknesses. Cost-plus contracts offer flexibility and potential for high-quality work but can be unpredictable in cost. Fixed-price contracts provide cost predictability and more straightforward billing but come with higher risk for contractors and less flexibility.

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