The Basics of Cost-Plus Contracts: A Comprehensive Guide

Zack Beveridge
April 9, 2024
best practices

Cost-plus contracts are a common arrangement in the construction industry, offering flexibility and transparency for both contractors and clients. In this comprehensive guide, we'll delve into the fundamentals of cost-plus contracts, including how they work, their benefits, key considerations for all parties involved, the legality of cost-plus contracts in states like California, and the distinction between cost-plus and time & material (T&M) contracts.

Understanding Cost-Plus Contracts

A cost-plus contract is an agreement in which the owner agrees to pay for all of a project's expenses, including the cost of labor, materials, and related expenses. These contracts also include provisions where owners agree to pay a percentage that covers the builder's overhead and profit.

Typically, the owner accepts more risk than the builder under a cost-plus contract, as the owner could end up paying much more for a project than the originally estimated cost. Different types of cost-plus contracts provide varying levels of risk to owners:

Cost Plus Fixed Fee: These contracts include a fixed fee to cover the builder's profit and overhead, in addition to coverage for variable costs such as materials and labor.

Cost Plus Fixed Percentage: The owner is responsible for paying for the cost of materials and labor for a project, along with a fixed percentage of this amount to account for the builder's profit and overhead.

Cost Plus with Guaranteed Maximum Price: Owners can generate savings through this type of contract because they pay for a project's associated costs and a fixed fee up to a specified maximum amount. This incentivizes builders to keep their expenses within the margin created by the guaranteed maximum price to maximize their own profits.

Benefits of Cost-Plus Contracts

Cost-plus contracts offer enhanced transparency, a key advantage for both contractors and clients. By reimbursing the contractor for actual costs incurred, these contracts provide clear visibility into project expenses, minimizing the potential for disputes over costs. Furthermore, cost-plus contracts afford flexibility to accommodate changes in project scope or unforeseen challenges, enabling seamless adaptation to evolving needs without major delays or cost overruns. With builders having greater flexibility in managing project costs, there's a greater probability of realizing the owner's vision for the project.

Key Considerations for Contractors in California

For contractors in California, navigating the landscape of cost-plus contracts demands acute attention to legal stipulations and consumer protection statutes. Particularly stringent are the regulations outlined by the Contractors State Licensing Board (CSLB), which vigilantly safeguards consumers against contractor malpractice. The CSLB, alarmed by instances of unauthorized work, overpayments, and project abandonment, enforces strict adherence to the Home Improvement Contract (HIC) laws. These laws dictate that HICs for residential projects exceeding $500 must meticulously detail aspects such as contract price, commencement and completion dates, work descriptions, deposit amounts, insurance disclosures, and obligatory warnings.

To ensure compliance, contractors must meticulously draft contracts, dedicating considerable space—sometimes up to six pages—to meet California's legal standards. The contractual language must adhere to specific formatting guidelines, with critical information required to be typed in boldface type and certain warnings mandated to be verbatim. Moreover, the contract's total sum must be expressed in dollars and cents, with progress payments outlined explicitly, referencing completed work and materials supplied.

Consequences for failing to comply with these rigorous regulations can be severe, potentially resulting in license revocation, criminal prosecution, or contract nullification at the homeowner's discretion. The CSLB wields authority to issue citations for non compliant contracts, levying fines of up to $5000.

Of note is the prohibition against time and materials (T&M) and cost-plus contracts in California for home improvement projects. Despite some confusion within the industry, these contract types violate HIC laws by failing to specify the total contract amount, commencement and cessation dates, and a firm payment schedule. The CSLB explicitly denounces such contracts as illegal, emphasizing the risks they pose to homeowners who may lack transparency regarding project costs, progress payments, and work completion.

In navigating the complex legal landscape of home remodeling contracts in California, contractors must exercise diligence to ensure compliance with HIC laws. Ignorance or oversight can result in costly repercussions, underscoring the necessity for contractors to obtain comprehensive understanding and adherence to regulatory statutes. By prioritizing legal compliance and adopting best practices, contractors can mitigate risks and safeguard both their reputation and clients' interests.

Time & Materials Contracts

In contrast to cost-plus contracts, time and materials contracts establish an hourly or daily rate for builders to work on a project. Owners also typically agree to pay for the cost of materials and other associated project expenses.

These contracts are usually useful for smaller projects or when owners can't accurately ascertain the scope of work necessary to complete a project. Price or project duration caps are often included in these contracts to limit how long a project can go on or how much it can cost the owner, incentivizing builders to complete the job within a specific timeframe or budget.

Understanding the differences between cost-plus and time & materials contracts is crucial for both contractors and clients when selecting the appropriate contract type for a construction project. Each type offers its own advantages and considerations, depending on the project's scope, complexity, and budgetary constraints.


Cost-plus contracts can be an effective tool for managing construction projects, providing flexibility, transparency, and shared risk between contractors and clients. By understanding how cost-plus contracts work, considering the benefits and key considerations involved, and ensuring compliance with relevant laws and regulations, both contractors and clients can enter into agreements with confidence, knowing that they have a framework in place to navigate the complexities of construction projects effectively.