You bid the second floor at normal production. Then the GC compressed the schedule, and now drywall, mechanical, and sprinkler are all working the same bay your rough-in crew is in.
Nobody is stopped. Everybody is slower. That is the stacking of trades labor impact electrical contractors absorb without ever filing a delay claim, because the job is not delayed — your crew is just getting less done per hour in a room that has too many people in it.
Then the invoice or the change request lands, and the GC asks why the east wing took 340 hours. If your answer is a timesheet total, you lose. If your answer is eleven dated daily entries showing crew size, who else was in that bay, and what got installed, you get paid.
If you bill time and material, stacking does not cost you the hours — it costs you the argument. Every one of those 340 hours is billable. But the owner was not standing in that bay, and a line reading 340 hours reads as padding when the same wing ran 8 hours a circuit last month and 12 this month. Nothing in a timesheet total explains the difference, so the discount you give to keep the relationship comes straight out of work your crew actually performed.Take the two halves of this article according to your contract. The daily record and the square-feet-per-worker sizing serve both — on T&M they explain the invoice, on fixed price they size the claim. The notice letter and the measured mile are for fixed-price scope, where you eat the overrun unless you go get it.
This is the whole method — the density arithmetic, the measured mile, the daily record, and a notice letter you can copy. No purchase required to use any of it.
What Stacking of Trades Looks Like on an Electrical Job
Stacking of trades is more crews working the same physical area than the area was planned for. The productivity loss happens while everyone is working, not while anyone is waiting on a schedule.
On electrical scope it shows up in a handful of predictable ways.
Above the ceiling. Your conduit and cable tray share the same plenum as duct, sprinkler main, and plumbing. Whoever gets there second works around the first. Rough-in blocked by finish trades. Sheetrock closes a wall before you have your boxes set and your homeruns pulled, so you come back and cut. Trim waiting on grid. Devices, fixtures, and terminations queue behind ceiling grid and drywall that are being installed in the same room you are standing in. Remobilization. You work an area, get pushed out, and come back three times. Every return costs setup, layout re-verification, and material handling that the bid paid for once. Ladder and lift conflicts. Two trades competing for the same overhead access point means one crew stands there.None of that is a delay. Nothing on the schedule slipped. You just burned more hours per circuit than you bid, and the hours are real.
How Much Productivity Does Stacking of Trades Cost?
Published research puts the productivity loss anywhere from zero to about 50%, depending on how much floor space each worker has — roughly no loss at about 191 net square feet per worker, and roughly 50% loss at about 90. Awad S. Hanna's article "The Stacking of Trades" (Electrical Contractor magazine, August 2004) plots percent lost efficiency against square feet per worker, from data collected on electrical projects by the Construction Engineering and Management program at the University of Wisconsin-Madison.
That model applies to projects in the range of about 2,000 to 150,000 man-hours, and to worker densities between 90 and 191 square feet per worker. Outside that range, treat it as a rough indicator, not a number to put in a claim.
The article carries the full curve as a printed graph. The table below is a straight-line reading between its two published endpoints, so you can look up an approximate value without it.
| Net sq ft per worker (all trades in the area) | Approximate lost efficiency |
|---|
| 191 or more | 0% |
| 180 | 5% |
| 170 | 10% |
| 160 | 15% |
| 150 | 20% |
| 140 | 25% |
| 130 | 30% |
| 120 | 35% |
| 110 | 40% |
| 100 | 45% |
| 90 | 50% |
Read that table honestly. It is linear interpolation between two published endpoints, not a reproduction of Hanna's curve, and it is a sizing tool — not evidence.
There is a second published reference point. The Mechanical Contractors Association of America publishes labor factors for conditions that impact productivity, and lists stacking of trades at roughly 10% for minor, 20% for average, and 30% for severe impact. Pull the current MCAA bulletin before you quote a factor in a change request, because these tables get revised.
Both sources estimate. Neither one measures your job. The measurement comes from your own records, which is the next section.
Example Arithmetic: Sizing the Impact on One Wing
Here is the density calculation run end to end. Every input is visible so you can swap in your own numbers.
| Input | Example value | Where it comes from |
|---|
| Gross work area | 2,400 sq ft | Second-floor east wing, off the floor plan |
| Less unusable space | 500 sq ft | Stair core plus stored ductwork |
| Net work area | 1,900 sq ft | 2,400 minus 500 |
| Workers in that area, all trades | 15 | 4 electricians, 6 drywall, 3 mechanical, 2 sprinkler |
| Net sq ft per worker | 127 | 1,900 divided by 15 |
| Approximate lost efficiency | 32% | Between the 130 and 120 rows above |
| Crew hours in that area | 352 | 4 electricians, 8 hrs, 11 working days |
| Estimated impacted hours | 113 | 352 times 0.32 |
| Rate used for sizing only | $95/hr | A round number for this example, not a recoverable rate |
| Order of magnitude | $10,735 | 113 hours times $95 — a sizing figure, not a claim amount |
On T&M this is hours you can bill but must be able to explain. On a fixed-price subcontract, what you can actually recover is set by the change-order pricing and markup language in your contract, not by your T&M bill rate.
That is example arithmetic, not a claim about your job. Its purpose is to tell you whether the condition is worth documenting, before you spend two weeks documenting it.
If the number comes back small, note it and move on. If it comes back like the example above, start the record today.
Why These Labor Impact Claims Get Denied
Most stacking claims die for one of three reasons, and none of them are about whether the impact was real.
No contemporaneous record. A claim built from memory after the job closes reads as a story. The GC has a story too, and theirs comes with a schedule attached. Late notice. Nearly every subcontract requires written notice within a stated number of days of the event. Miss it and the math never gets read. One lumped number. "The east wing overran by 340 hours" is a total, not evidence. The GC cannot tell overrun from bad estimating, and neither can you.The fix for all three is the same daily record, and it has to exist while the condition is happening. There is no way to reconstruct it later that survives scrutiny.
What Your Foreman Writes Down That Day
Five fields, one line, at the end of the shift. This is the entire mechanism, and it is worth more than any analysis you buy afterward.
- Date and hours — actual in and out, not a rounded total.
- Who — your crew size in that area, by name.
- Where — the specific area. Floor, wing, room numbers, or bay grid.
- Who else was in that area — the other trades and roughly how many of each.
- What got done, and what stopped it — installed quantity against planned, and the specific blockage.
A record that says 8.77 hrs proves nothing. It survives payroll and loses every argument after that.
A record that says this ends the argument:
Thu 7:02a–3:48p — 4 men, 2nd flr east wing, bays E4–E9. Sheetrock (6) and mechanical (3) in the same bays all day. Pulled and terminated 6 of 18 planned circuits. Lost about 2h20m waiting on ceiling access above E6.
That is one line a foreman can write on a clipboard in under two minutes. It carries crew size, area, competing trades, production against plan, and the specific loss.
The obstacle is real: electricians do not write narrative reports, and a form that asks for a paragraph comes back blank. Ask for one line about what got done and who was in the way, and you get it — because the crew understands that line is what stops a customer or a GC from chiseling them on work they actually performed.
Where you keep it matters less than whether it exists. A printed daily field report on a clipboard works. So does a phone photo of that sheet, texted to the office nightly. So does a time tracking app that asks "what did you work on?" at clock-out and prints the dated notes next to the hours — FieldTimesheet does that part, though you still add the other-trades headcount and area yourself, because no time clock knows how many drywall hands were in your bay. The free T&M Billing Backup Kit includes a printable daily field report if you want to start on paper tomorrow.
Whatever you use, the note has to be written the same day, by the person who was there.
How a Measured Mile Works, and What It Needs From You
A measured mile compares your own crew's production during a clean period against the same crew's production during the impacted period, on the same scope. It is the method claims analysts prefer because it uses your job as its own control.
AACE International's Recommended Practice 25R-03, on estimating lost labor productivity, treats the measured mile as the preferred approach when the data supports it. It beats industry factor tables because it is your actual production, not an average.
Here is the comparison, with example numbers.
| Period | Crew | Hours | Circuits complete | Hours per circuit |
|---|
| Baseline week (area clear) | 4 electricians | 160 | 20 | 8.0 |
| Impacted week (4 trades in area) | 4 electricians | 160 | 13 | 12.3 |
The difference is 4.3 hours per circuit. Across the 13 circuits completed in the impacted week, that is about 56 hours of lost production for that week alone, or roughly a 35% productivity drop.
That 35% lands near the density table's 32%, which is worth noticing but is not corroboration. The density estimate is a sanity check on the measured mile, not a second proof — both run on your headcount and your area, so they are not independent. Only the measured mile goes in the package.
To run this you need four things your daily record already has: the date, the crew, the area, and a countable unit of work completed. Circuits, devices, fixtures, feet of tray, panels — pick one unit and count it every day.
Be straight about the limits. A measured mile on a large claim is expert work, and a consultant or attorney will run the analysis. Your job is to produce inputs clean enough that the analysis is possible at all.
Written Notice: The Clock That Kills Claims Before the Math Matters
Send written notice as soon as you identify the condition, not when you price it. Your subcontract states the window in days, it is usually short, and it usually starts at the event rather than at the invoice.
Pull your subcontract and find the notice article before you need it. Then send something like this.
[Date]>
To: [GC project manager], [GC company]
Re: [Project] — notice of labor impact, second-floor east wing. Subcontract [#], Article [#] (Notice).>
This is written notice under the subcontract that our labor is being impacted by trade congestion in the second-floor east wing beginning [date].>
Since [date], drywall, mechanical, and sprinkler crews have worked the same bays as our rough-in crew. Our daily reports for [date range] record crew size, other trades present in the area, and work completed each day. Copies are attached.>
Production in that area has moved from [X] hours per circuit to [Y] hours per circuit, same crew and same scope. We are tracking the added hours separately as of [date].>
We are not stopping work and we are not requesting a schedule change. We are preserving our right to recover the added labor cost, and we will submit a priced change request when the impact ends or on [date], whichever comes first.>
Please advise whether the area can be sequenced so fewer trades work it at one time.>
[Name], [Title]
Two things that letter does deliberately. It attaches the record instead of promising one, and it asks for a fix — which makes it a coordination request rather than an opening threat.
Send it to the person named in the subcontract for notices, and keep proof of delivery. An email to a project manager who is not the notice recipient is not notice.
Electrical Ways to Pull Hours Out of a Crowded Area
Some of this you can do even after the stacking has started. Document it either way, because mitigation you paid for is recoverable too.
Prefab off site. Assemblies built in the shop remove crew hours from the congested area entirely. Log the shop hours separately so the shift shows up in the record. Resequence within your own scope. Move to a floor or wing that is clear and come back. Track the remobilization hours as their own line, because they are a direct cost of the stacking. Second shift on the tight areas. Working the crowded bay when nobody else is in it converts a density problem into a premium-time problem, which is easier to price. Coordination drawings for the plenum. If above-ceiling congestion is the constraint, a coordinated overhead drawing settles who goes where before three crews find out in person. Bank material at the point of use. Congested areas make material handling expensive. Staging closer cuts travel that nobody bid.Every one of these has a cost. Put that cost in the record on the day you incur it, or it disappears into the same lump the GC will question later.
Start Documenting at Half Complete, Not When the Argument Starts
The same Hanna article reports a survey of NECA member contractors that asked them to assign stacking across four quartiles of a project's duration. They put nearly half of it in the final quartile and almost a third in the third quartile. Stacking is a late-schedule condition.
That gives you a trigger instead of a judgment call. At roughly 50% complete on any job with more than a couple of trades, turn on the daily area record whether or not anything looks wrong.
It costs a foreman one line at the end of the shift. If stacking never happens, you have a clean production history that makes your next bid better and your job costing honest.
If it does happen, you already have the one thing that cannot be created after the fact. The same dated, specific record that wins this argument with a GC is what settles a T&M invoice dispute with an owner, and it is the same data that makes job costing for electricians mean something. You are not keeping three records. You are keeping one.
If you want to see what that record looks like when it is printed as backup for a customer, there is an annotated sample billing packet you can read without signing up for anything.
Frequently Asked Questions
What is stacking of trades in construction?
Stacking of trades is more crews working in the same physical area than the area was planned to hold. Everyone keeps working, but each crew gets less done per hour because of congestion, competing access, and interference.
How much productivity do electrical contractors lose to trade stacking?
Published research by Awad S. Hanna at the University of Wisconsin-Madison — "The Stacking of Trades," Electrical Contractor magazine, August 2004 — puts the loss near zero at about 191 net square feet per worker and near 50% at about 90 square feet per worker, for projects between roughly 2,000 and 150,000 man-hours. MCAA's labor-factor bulletin lists stacking of trades at roughly 10% minor, 20% average, and 30% severe. Both are estimates — your own production records are the measurement.
How do I calculate square feet per worker on my job?
Take the gross area your crew is working, subtract space nobody can work in (stair cores, shafts, stored material), then divide that net area by the total headcount from all trades in that area on that day. Count everybody, not just your crew.
Is stacking of trades the same thing as a delay claim?
No. A delay claim is about time — the schedule slipped. A stacking or disruption claim is about productivity — the schedule may be fine, but your crew burned more hours per unit of work while they were working. They are different claims with different proof, and mixing them weakens both.
Does trade stacking matter if I bill time and material?
Yes, but differently. On T&M the hours are billable, so stacking does not cost you the labor — it costs you the invoice argument, because the total looks inflated and nothing in a timesheet explains why. The same dated daily record that supports a fixed-price claim is what keeps a T&M invoice from getting discounted.
What should my foreman write down when the area is overcrowded?
Date and actual hours, crew size and names, the specific area, which other trades were in that area and roughly how many, and installed quantity against planned with the specific blockage named. One line per day is enough if it contains all five.
Do I have to give the GC written notice before I can recover labor impact costs?
Almost always, and the window is short. Your subcontract names the notice article, the number of days, and who the notice goes to. Send it when you identify the condition, not when you price it, and keep proof of delivery.
Can I claim stacking of trades if my timesheets only show total daily hours?
It is much harder. Total hours prove you spent money; they do not prove why. Without crew, area, other trades present, and completed quantity by day, there is nothing to run a measured mile against and nothing to separate impact from estimating error.
Who is responsible for stacking of trades, the GC or the subs?
Coordination and sequencing of the trades is normally the general contractor's responsibility under most subcontract forms, but responsibility depends on your specific contract language, including any no-damage-for-delay or coordination clauses. Read your subcontract, and if real money is involved, have a construction attorney read it too.