When a developer or owner sits down to negotiate project delivery, one of the most consequential decisions involves the contract structure. A cost plus construction contract is one of the most commonly discussed alternatives to a fixed-price arrangement, and it tends to generate questions around risk, transparency, and how costs are controlled. Understanding how cost plus agreements work, what they include, and where they perform best helps owners make informed decisions before any trade is hired or a project schedule is committed.
What Is a Cost Plus Construction Contract?
In a cost plus contract, the owner pays the actual cost of labour, materials, equipment, and subcontracts – the direct project costs – plus a defined fee or markup that compensates the contractor or construction manager for services and overhead. The cost component is open-book and documented through invoices and certified trade accounts, while the plus is either a fixed fee or a percentage agreed to upfront. This structure differs fundamentally from a lump sum contract, in which the contractor assumes all cost risk in exchange for a fixed price that embeds profit and contingency into the number.
Cost plus arrangements are most common on projects where scope is not fully defined at the time of engagement, where design is still evolving, or where the owner wants direct control over subcontract procurement. They are also a natural fit for phased delivery, where early site work begins before the complete design package is available.
What Costs Are Included?
The cost component of a cost plus contract typically covers all direct expenditures tied to project execution: subcontractor trade costs including labour and materials, equipment rental and operation, temporary facilities such as site trailers and fencing, permits and municipal fees, testing and inspection costs, and in some structures, wages for onsite supervision personnel. What should be explicitly excluded are home office overhead, duplicate general conditions items, and any costs not tied to the specific project.
Clear definitions of reimbursable costs are essential before signing. Disputes in cost plus contracts often arise not from the plus component but from disagreements about what counts as a legitimate cost. A well-structured agreement will specify cost categories, documentation requirements, and exclusions with enough precision that both parties are aligned before construction begins.
How the Fee or Markup Is Structured
The plus in a cost plus arrangement takes two common forms: a percentage of total construction cost or a fixed fee negotiated at the outset. A percentage-based fee – which mirrors the structure described in more detail in the post on construction management fees – compensates proportionally to the project’s scale, but can create an incentive to allow costs to grow if not paired with strong owner oversight and audit rights. A fixed fee eliminates that incentive and provides absolute cost certainty on the management component regardless of whether the overall project comes in under or over estimate.
Some owners prefer a hybrid approach combining a fixed fee for pre-construction and procurement with a percentage for active construction once scope is better understood. The right structure depends on how much cost definition exists at the time of signing and how much budget flexibility the owner requires going into the build.
Managing Risk and Scope in a Cost Plus Project
The primary trade-off in a cost plus arrangement is that the owner absorbs the cost risk a general contractor would carry under a lump sum structure. If market conditions shift or subcontractor bids come in above estimate, those costs flow directly to the owner. Rigorous tracking of construction change orders becomes especially important in a cost plus project, because scope growth is a direct cost to the owner rather than a negotiation with a fixed-price contractor.
A disciplined approach to construction risk management – identifying and pricing risk before work begins – reduces the likelihood of cost surprises mid-build. Owners working under a cost plus structure should require regular budget reconciliations and insist that their construction manager flag scope changes before costs are committed rather than after.
Cost Plus vs. Lump Sum: Choosing the Right Structure
Cost plus contracts tend to be the right choice when scope is incomplete or evolving, when fast-track delivery is required before design is finalized, or when the owner wants maximum transparency and direct control over trade procurement. Lump sum structures make more sense when design is fully developed and the owner’s priority is transferring cost risk in exchange for price certainty.
In practice, many commercial and multi-family projects across the Okanagan use a construction management model that captures the transparency of cost plus while adding professional procurement discipline. The construction manager acts as the owner’s agent, procuring trades competitively and passing costs through at actual value rather than inside a fixed markup.
How Team Construction Approaches Cost Plus Contracts
At Team Construction Management, we bring open-book cost management to every project we oversee, giving owners full visibility into trade costs, budget performance, and scope decisions from procurement through handover. If you are evaluating contract structures for an upcoming commercial or multi-family development in Kelowna or across the Okanagan, contact our team to discuss how the right delivery model can protect your budget from day one.
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