A schedule of rates in construction contracts is a pre-negotiated price list that assigns a fixed cost to every unit of labor, material, or task, so the parties pay based on the quantities actually built rather than a single lump sum agreed up front. Each line item pairs a task or material with a unit of measurement — cubic yard, linear foot, hour — and a locked-in price. The total contract value is not known until the work is measured and complete.
This arrangement, sometimes called a unit-price or re-measurement contract, suits projects where the full scope is uncertain at signing: maintenance programs, infrastructure rehabilitation, work behind existing walls or underground, and indefinite-delivery arrangements where an owner expects a stream of small projects over a fixed term.
How It Differs From a Lump-Sum Contract
In a lump-sum contract, the contractor commits to one total price for a defined scope. If actual quantities come in lower, the contractor keeps the difference; if they run higher, the contractor absorbs the loss. A schedule of rates flips that risk. Unit prices are locked in, but the overall payment adjusts as quantities are measured on site. Neither party knows the final cost until the work is done, and the owner carries the exposure to quantity overruns in exchange for pricing transparency on each component.
What Goes Into the Schedule
Each line item describes a discrete task or material, paired with a unit and a price. Concrete might be priced per cubic yard, electrical conduit per linear foot, painting per square foot, skilled labor per hour. The prices are fully burdened: a single unit rate typically absorbs the base wage or material cost, payroll taxes, workers’ compensation premiums, employee benefits, equipment wear, and an allocation for overhead and profit. The rate a client sees on the schedule is well above the raw cost of the underlying input.
Beyond the recurring task items, most schedules include separate lines for one-time or project-wide costs:
- Mobilization and demobilization — transporting equipment to the site, setting up temporary offices, installing fencing, and securing permits before the first billable task begins. Owners often cap this line at 5 to 10 percent of the total contract value.
- Preliminary items — site surveys, traffic management, temporary utilities, and environmental protections that apply to the project as a whole.
- Provisional sums — allowances for work that cannot be fully defined at tender time, such as unforeseen ground conditions, held in reserve and released only when needed.
Where the Rates Come From
Some markets rely on published rate books that act as a common pricing language. The UK’s National Schedule of Rates, published for over 30 years, is a pre-priced list of typical maintenance tasks used across public and private sectors to value repairs and maintenance work.1Society of Construction and Quantity Surveyors. National Schedules of Rates Tenderers receive the base rates and adjust them by a percentage to reflect their own overhead, profit, and regional cost factors.2Gordian. Gordian Releases 2025/2026 UK National Schedule of Rates The United States has no single equivalent, but agencies and estimators often benchmark unit prices against published cost databases such as RSMeans, which provides unit, assembly, and square-foot pricing across residential and commercial categories.3RSMeans. 2026 Residential Cost Data CD
When specialized work falls outside any published list — unusual finishes, proprietary systems, site-specific remediation — the parties develop a bespoke schedule from scratch. These custom documents are common in private development where the scope is too unique for off-the-shelf pricing to mean much.
Bidding on a Schedule of Rates
During tender, the client issues the schedule with item descriptions and estimated quantities but no prices. Each bidder inserts its own unit price for every listed item. Because the quantities are estimates, the contractor is committing to a rate per unit without knowing exactly how much of each item will ultimately be installed. The client then extends each bidder’s unit prices by the estimated quantities and compares the totals side by side.
The format is common in federal indefinite-quantity contracts, where agencies contract for an unknown number of small projects over a fixed period at defined unit prices for each category of work.4Acquisition.GOV. Federal Acquisition Regulation Part 16.504 – Indefinite-Quantity Contracts Progress payments on federal construction work are then made monthly based on approved estimates of work accomplished that meet the contract’s quality standards.5Acquisition.GOV. Federal Acquisition Regulation 52.232-5 – Payments Under Fixed-Price Construction Contracts
The Unbalanced-Bid Problem
The bid-comparison process has a well-known vulnerability. Because the client’s quantities are estimates, a contractor can manipulate its unit prices to gain an advantage. A bid is considered mathematically unbalanced when some items carry nominal prices while others are inflated, so that each item does not carry its proportionate share of total cost plus profit.6Federal Highway Administration. Rejection of Unbalanced Bids
Two tactics are typical. Front-loading means overpricing work performed early in the project and underpricing later items, which effectively hands the contractor an interest-free loan from the client’s early overpayments. Quantity gambling means overpricing items the contractor expects to overrun the estimate and underpricing items likely to underrun; if the guess is right, profit on overruns swamps the loss elsewhere.
A materially unbalanced bid — one that creates reasonable doubt the apparent low bidder will actually deliver the lowest total cost — can be rejected outright.6Federal Highway Administration. Rejection of Unbalanced Bids Federal policy requires unit bid items to be evaluated for reasonable conformance with the engineer’s estimate, and extreme variations should be flagged before any contract is awarded.
Measuring Work and Getting Paid
Once construction starts, payment depends on physically verifying what was built. A quantity surveyor or site engineer inspects completed work and measures the actual quantities installed during the billing period. Notes taken during these inspections are used to assess the approximate quantity and value of partially completed items.7Royal Institution of Chartered Surveyors. Interim Valuations and Payment Verified quantities are multiplied by the corresponding unit prices from the schedule to produce the interim valuation. Install 500 feet of cabling at $10 per foot and the payment application reflects a $5,000 charge for that item, with no negotiation over value.
The proper method is to value, on each occasion, the total amount of work completed since the project started, then subtract what has already been paid. That cumulative approach catches errors that would slip through if each month were valued in isolation.7Royal Institution of Chartered Surveyors. Interim Valuations and Payment
Retainage
Most contracts withhold a percentage of each progress payment as retainage, a financial cushion that protects the client if the contractor fails to finish or correct defective work. The typical range is 5 to 10 percent. On federal construction contracts, the contracting officer may retain up to 10 percent of progress payments if satisfactory progress has not been achieved, and must release the withheld funds promptly once all contract requirements are complete.5Acquisition.GOV. Federal Acquisition Regulation 52.232-5 – Payments Under Fixed-Price Construction Contracts When progress is satisfactory, the payment should be authorized in full without retention. As the project nears completion, retainage is often reduced.
When Quantities Swing Hard
Unit prices assume a certain volume of work. When actual quantities deviate dramatically from the estimates, the economics behind those prices can break down, because fixed costs like mobilization and supervision get spread differently across a much larger or smaller scope.
Federal construction contracts handle this with a variation-in-estimated-quantity clause. When the actual quantity of a unit-priced item varies more than 15 percent above or below the estimate, either party can demand an equitable adjustment to the contract price. The adjustment applies only to the portion that exceeds 115 percent or falls below 85 percent of the original estimate.5Acquisition.GOV. Federal Acquisition Regulation 52.232-5 – Payments Under Fixed-Price Construction Contracts Standard AIA general conditions take a different approach, allowing adjustment whenever the quantity change is large enough that applying the original unit prices would cause “substantial inequity” to either side, a more flexible but less predictable standard.
If a contract lacks a clear variation-in-quantity clause, the contractor is stuck with the agreed rate regardless of volume. That can create incentives to cut corners when quantities overrun or to drag out work when they underrun.
Pricing Scope Changes
Design changes, unforeseen site conditions, and client-requested additions are inevitable. The schedule gives both sides a ready-made pricing tool. If new work resembles an existing line item, the pre-agreed rate applies to the additional quantities, and the project keeps moving. A change order adding 200 more linear feet of the same ductwork already on the schedule is priced at the same per-foot rate.
When a variation involves work that doesn’t match any existing item, parties typically derive a fair rate by analogy to the closest comparable items, adjusting for differences in complexity or materials.
Constructive Changes
Not every scope change comes through a signed order. Sometimes an owner’s representative gives verbal instructions on site, or issues drawings that quietly expand the contractor’s obligations. Under the constructive change doctrine, a contractor who performs work beyond the contract minimum at the direction of the owner — even without a formal change order — can recover the additional cost. The contractor must prove the work exceeded the original scope and that the owner or its agent required the performance, whether by words or conduct.6Federal Highway Administration. Rejection of Unbalanced Bids Voluntary work doesn’t qualify. An existing schedule of rates simplifies valuation of these claims because applicable unit prices are already agreed. Documentation is the critical step; contractors who don’t track extra work in real time often can’t prove entitlement later.
Price Escalation on Long Projects
A schedule locked in at signing can become stale over a long project. Material prices shift, labor markets tighten, fuel costs move. Multi-year contracts typically address this with a price escalation clause tied to a recognized economic index. Common choices include the Producer Price Index for construction inputs and the Consumer Price Index for broader cost-of-living changes. Contracts may also reference sector-specific benchmarks like the Engineering News-Record construction cost indices or RSMeans regional modifiers.
The mechanics vary. A typical clause triggers when the relevant index moves beyond a defined threshold, often 3 to 5 percent, during a specified period, and adjusts unit rates proportionally. Many clauses include a cap on increases and a floor to protect the contractor from being forced to absorb deflation beyond a set limit. The base period, adjustment frequency (monthly, quarterly, or annually), and the formula for the new price all need to be spelled out to avoid ambiguity. Contracts without an escalation clause effectively force the contractor to gamble on future costs, which tends to inflate initial pricing as a hedge.
Records You Need to Keep
Because payment under this structure depends on measured quantities rather than a fixed price, documentation matters more than in most other contract types. Every payment should trace back to a verified measurement, a specific line item, and an approved rate.
On federal contracts, the retention requirements are explicit. Contractors must keep all books, documents, accounting procedures, and supporting evidence available for at least three years after final payment.8Acquisition.GOV. Federal Acquisition Regulation Subpart 4.7 – Contractor Records Retention If a contractor misses the deadline for submitting final indirect cost rate proposals, the retention period extends automatically, one extra day for each day the submission is late.
Even outside the federal context, keeping detailed records of site measurements, payment applications, change orders, and rate adjustments is essential. Disputes over quantities or rates can surface months or years after the work is finished, and the party with better documentation almost always has the stronger position.