Guides

What Is a Labor Rate Build-Up (LRBU)? A Guide for Construction Contractors

Updated Jul 12, 2026

If you price time-and-materials work in construction — any T&M work, in any sector — there is one number your whole job rides on: the billable labor rate — what one hour of one trade actually costs your client. It doesn't matter whether that hour belongs to a pipefitter on an industrial change order, an electrician on a service call, or a carpenter on a remodel that went T&M the moment the walls came open. A labor rate build-up (LRBU) is the calculation that produces that number: it starts from the bare wage and stacks on everything an hour really costs you — benefits, payroll taxes, insurance, overhead — then adds your markup, with separate results for straight time, overtime, and double time.

Estimators have done this math forever, usually in a spreadsheet tab nobody else can follow. But the term itself is rarely written down, and the mechanics are full of traps that quietly move real money. This guide defines the LRBU properly and walks one dollar all the way through a real build-up.

In this guide:

• The short answer
• Why T&M work lives or dies on it
• The anatomy of a build-up
• A worked example, penny by penny
• Why the overtime rate is not 1.5× the straight-time rate
• Margin vs. markup — the finalize step
• The five mistakes that move real money
• From wages to rate sheet

The short answer

A labor rate build-up is a layered calculation — a column of costs, summed the way an estimator's tape would run it:

Run once per pay tier — straight time (ST), overtime (OT), double time (DT) — because, as we'll see, the layers do not all scale together when the wage goes to premium pay. The output is the rate sheet you attach to a T&M contract or change order: one defensible billable rate per craft, per tier.

Why T&M work lives or dies on it

T&M pricing shows up in far more of construction than the contracts that say "time and materials" on the cover:

• Change orders — on every delivery type. Even a pure lump-sum contractor lives on T&M rates, because changed and added work is priced from a labor rate sheet when the scope can't be pre-measured. Industry analyses put change orders at 10–15% of total contract value on major projects, and past 25% on troubled ones — that slice of the job is priced by your build-up, not your bid. (Pricing change orders on T&M — caps, force account, mid-job steps — is its own guide.)
• Service and maintenance work. The electrician's or mechanical contractor's "shop rate" on a service ticket is an LRBU by another name — a wage, its burdens, truck and tooling overhead, and margin folded into one billable hourly number.
• Renovation and remodel. Hidden-condition work goes T&M precisely because nobody can fix a price for what's behind the wall; the rate sheet is agreed before demolition starts.
• Force account and emergency work. On public projects the owner often dictates the shape of the build-up — several state DOTs publish fixed fringe and markup structures for force-account labor and audit against them line by line.

On a lump-sum bid, a labor-rate error hides inside your number and you simply make less than you thought. On T&M work the rate itself is the contract. It gets negotiated up front, printed on the change order or service agreement, and — on public force-account work and big audited sites especially — checked later by someone whose job is to find the padding.

That cuts both ways:

• Set the rate too low — forget a burden, use last year's benefit rates — and you eat the difference on every hour, for the life of the job.
• Set it too high in a way you can't defend — a blanket multiplier, a double-counted deduction — and the auditor strikes it, or the client's estimator beats you up in negotiation and takes your credibility with it.

A single change order might be a crew of six for a month — call it 1,000 hours — and change orders come in strings, not singles: across a job they can add up to 10,000 T&M hours or more. At that scale a $1/hour error is a $10,000 error, and a bad overtime convention (we'll quantify one below) is several times that.

The anatomy of a build-up

Every build-up has the same skeleton. What varies — by agreement, by state, by your insurance program — is the numbers and the bases.

Sum the layers and you have your hourly cost — what the hour costs you before profit. The finalize step (below) turns cost into the billable rate.

A worked example, penny by penny

Here is a real build-up shape, using a union carpenters agreement: base wage $46.28, a $1.86/hour wage-attached addition, and $15.93/hour in benefit contributions. Burdens: FICA 6.2% + Medicare 1.45% + FUTA 0.6% + SUI 4.75% (13.0% total) on taxable wages; WC 4.75% + GL 4.5% (9.25%) on the straight-time taxable base per the insurance program; $0.65/hour flat for PPE, tools, and training. Finalize: 15% margin on cost. (The percentages are illustrative — your SUI and WC rates are your own. Open-shop math is identical in shape: swap the trust-fund contributions for your per-hour health-plan, retirement, and PTO costs.)

Components shown rounded to cents for readability; the cost and rate rows are computed on the unrounded values and quantized once, at the end. Do the same in your own sheet — rounding every intermediate line drifts the total.

First, notice the scale of what sits on top of the wage: this crew's straight-time hour costs $75.43 against a $46.28 wage — 63% over, before any profit. That gap is why pricing labor at "the wage plus a little" systematically underbills, in any sector: the burdens are not a rounding error, they are a third of the cost. (To run this math on your own numbers, use the free three-tier calculator in the fully burdened labor rate guide.)

Then read down the OT column and notice what moved and what didn't. The wage went up 50%. The payroll burdens followed it, because they attach to the check. The benefit contributions did not move — $15.93 per hour worked, at any tier. Neither did WC/GL (straight-time-rated program) nor the $0.65 of consumables. That asymmetry is the single most important fact about labor rate build-ups, and it is why the next section exists.

Why the overtime rate is not 1.5× the straight-time rate

The most common shortcut in T&M pricing is to build the straight-time rate honestly and then multiply it: OT = ST × 1.5, DT = ST × 2. Run that against the honest math — same crew, same hour:

+$13.60 per overtime hour you can't defend — and the same shortcut on double time bills $177.48 against an honest $150.27: +$27.21/hr. (Straight time matches by definition: $88.74 either way.)

The multiplier overstates this OT rate by $13.60 an hour, because it scales the layers that don't scale — the $15.93 of benefits, the straight-time-rated insurance, the consumables — right along with the wage. Acceleration and out-of-sequence work make change orders OT-heavy — run 1,500 OT hours through that shortcut and it's over $20,000 of rate sheet you cannot defend in an audit. And before the audit ever happens, it's a quoted OT rate a sharp client-side estimator will pick apart in negotiation — or an uncompetitive number that loses you shift work and weekend scopes you'd have won at the honest rate.

The direction can even flip. In an agreement where more of the package rides the check and the burdens are mostly percentages, the blanket multiplier can come in under the honest OT rate — and now you're donating the difference. The multiplier isn't conservative or aggressive; it's just wrong, in whichever direction your cost structure points. Build each tier from its own wage. (That settles what an OT hour bills; which hours are OT — daily caps, 4×10s, Sundays, holidays — is schedule math, worked with real weeks in Overtime & Double-Time Math.)

Margin vs. markup — the finalize step

Cost becomes a billable rate by one of two conventions, and they are not interchangeable:

• Margin on cost: rate = cost ÷ (1 − margin). The example above: $75.43 ÷ 0.85 = $88.74. A 15% margin means 15% of the rate is yours.
• Markup lines: rate = cost + a stack of percentages, each on a stated base — overhead as a percentage of total cost, profit as a percentage of the base wage, a 20% markup on the tier wage, whatever your contract or your book says. 15% markup on the same cost gives $86.75 — two dollars an hour less than the 15% margin number.

Neither is more correct; what matters is that your rate sheet, your contract language, and your math all say the same thing. "15%" with the convention left unstated is a $2/hour ambiguity — per hour, per craft, for the life of the job.

The five mistakes that move real money

1. Billing premium tiers by multiplier. Covered above. The flat layers don't scale; build each tier from its own wage.
2. Double-counting the package. If you work under a union agreement, the rate sheet publishes a bolded total package: wage plus employer contributions. They also list employee-side deductions — dues check-off percentages, vacation withheld from the wage, market-recovery deductions. Those come out of the wage, which means they're already inside it. Add them on top and you've billed them twice; an auditor who knows the agreement will find it in minutes. (Reading the schedule correctly is its own skill — see Union Schedule A, explained.)
3. Taxing the trust funds. Payroll burdens apply to what rides the paycheck — the wage and its taxable additions — not to benefit contributions paid into funds. Run 13% over the whole package and you've invented roughly $2/hour of phantom burden in the example above.
4. Letting WC and GL scale with premium pay. If your program rates overtime at straight-time equivalent, computing WC on the OT wage overstates the OT rate — same failure as the multiplier, smaller dose. Mirror your actual policy.
5. Stale rates. Union agreements step on scheduled dates, health plans renew mid-year, workers' comp gets re-rated, and your SUI rate resets every January. A build-up is only as good as its effective date — date your rate sheets, and re-run them when anything underneath moves.

From wages to rate sheet

None of this math is exotic — it's six layers and a division. What makes it dangerous is where it usually lives: a spreadsheet with the conventions in one estimator's head, the effective dates unmarked, and the OT column secretly a =B4*1.5.

This is the problem CrewMix was built around. You define the build-up once — your burdens, your bases, your finalize convention — and it prices every trade's ST, OT, and DT honestly, from each tier's own wage, with the full layer-by-layer breakdown preserved as the audit trail. Your wages can come from anywhere: a union Schedule A (the AI import reads the wage and contribution tables straight off the PDF), a prevailing-wage determination, or your own payroll numbers typed in directly — either way, the LRBU builder shows every rate recomputed live as you set your burdens. Rates are snapshotted into each estimate, so a later rate change never silently reprices signed work.

However you build yours — spreadsheet or software — build it in layers, label the bases, date it, and never let a multiplier near the premium tiers.