Prevailing Wage vs Union Wage: What's the Difference?

Definitions: Prevailing Wage vs Union Wage

Although the two terms often get used interchangeably, they are not the same thing.

Prevailing wage is a government-set minimum hourly wage (plus fringe benefits) for a specific construction classification in a specific geographic area. It is determined by the U.S. Department of Labor (or state equivalents like the California DIR) through wage surveys and is the legal floor for workers on covered public projects.

Union wage is the hourly wage (plus benefits) negotiated between a labor union and an employer (or employer association) through a collective bargaining agreement (CBA). It is a private contractual rate that applies to workers covered by that CBA.

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How Prevailing Wages Are Determined

The U.S. Department of Labor conducts wage surveys by county and construction type (Building, Heavy, Highway, Residential) and publishes the results as wage determinations on SAM.gov. The DOL surveys contractors, asking them to report wages paid to each classification on recent projects. The methodology:

• If a majority (over 50%) of surveyed workers in a classification earn the same rate, that rate is the prevailing wage
• If no single rate has a majority, the DOL uses the weighted average of all reported rates
• Surveys are updated periodically, with new determinations published on SAM.gov

Learn more in our guide on how to find and apply prevailing wage determinations, or look up rates now with our prevailing wage lookup tool.

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How Union Wages Are Determined

Union wages are the product of collective bargaining between a labor organization and either an individual employer or an employer association. Key characteristics:

• Negotiated on multi-year cycles (typically 3 to 5 years)
• Apply only to workers covered by the CBA
• Include detailed classifications, wage scales, and fringe contribution schedules
• Often include scheduled annual increases
• Enforced through grievance procedures under the CBA, not the DOL

Union rates reflect what the union and the employer have agreed to pay. They are typically higher than non-union rates in the same market because unions have negotiated leverage and include richer benefit packages.

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When Prevailing Wages Match Union Rates

In many metropolitan areas, the prevailing wage is identical to the union rate. This happens when a majority of surveyed workers in that classification are union members, because the 50%+ rule awards prevailing wage status to the single most common rate. In practice:

• In most major East Coast and West Coast metros, the prevailing wage for trades like Electrician, Plumber, and Ironworker often exactly matches the local union rate
• In heavy union markets like NYC, Chicago, and Los Angeles, prevailing wage determinations essentially mirror the corresponding union CBA
• Fringe benefit rates also track union benefit schedules in these markets

This alignment means that in union-dominant markets, non-union contractors working on federal projects effectively pay union-scale wages even if their workers are not union members.

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When Prevailing Wages Differ From Union Rates

Prevailing and union rates often diverge in:

• Lower-union-density markets: In southern and rural markets, the weighted-average prevailing wage can be substantially lower than any local union scale
• Certain trades: Laborer classifications often have lower union density than Electrician/Plumber, leading to gaps
• Small counties: When DOL survey response is thin, prevailing wages may draw from non-union rates
• Mid-year union increases: When a CBA's scheduled increase pushes union rates past the frozen federal determination

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Worked Comparison Example

Here's a realistic comparison for an Electrician in two different markets in 2026:

New York County, NY (union-dense market):

• IBEW Local 3 union rate: $62.75 base + $41.30 fringe = $104.05 total
• Federal prevailing wage (Davis-Bacon): $62.75 base + $41.30 fringe = $104.05 total
• Match — prevailing wage mirrors union scale

Greenville County, SC (lower-union-density market):

• IBEW Local 776 union rate: $38.50 base + $22.15 fringe = $60.65 total
• Federal prevailing wage (Davis-Bacon): $28.40 base + $9.85 fringe = $38.25 total
• Gap of $22.40/hr — union rate exceeds prevailing wage

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What Happens When Union Shops Do Federal Work

A union-signatory contractor working on a Davis-Bacon project must:

• Continue paying union wages and making union benefit contributions per the CBA
• Verify that union rates meet or exceed the applicable prevailing wage determination
• Submit WH-347 certified payroll like any other contractor
• Report the actual rate paid (usually union scale) in Column 6A of the WH-347

Because union rates usually meet or exceed prevailing wage, union shops rarely have to adjust their pay practices on federal work. Their compliance risk centers on proper reporting, classifications, and fringe fund documentation rather than underpayment.

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What Happens When Non-Union Shops Do Prevailing Wage Work

Non-union contractors on federal projects must:

• Look up the applicable prevailing wage determination before bidding
• Pay every worker at least the prevailing base rate
• Either pay the fringe rate in cash or make equivalent contributions to a bona fide benefit plan
• Ensure their regular non-federal pay scale does not drag their federal work below prevailing wage

For non-union shops, prevailing wage work often means temporarily paying higher rates than their standard scale. This is why bid estimates for federal work must carefully account for prevailing wage rates: bidding with your standard scale and then paying prevailing wage is a path to losing money on the project.

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Compliance Implications by Scenario

• Union shop, private work: Union CBA applies, no Davis-Bacon
• Union shop, federal work: Pay union rate (which typically meets prevailing wage), submit WH-347
• Non-union shop, private work: Market rates apply, no Davis-Bacon
• Non-union shop, federal work: Must pay prevailing wage (base + fringe), submit WH-347
• Non-union shop, federally-assisted state project: Higher of state prevailing wage or federal wage applies

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