Scheduling for Subcontractors

The schedule runs the job. If you don't understand it, you're flying blind — reacting to phone calls instead of planning your work. This guide covers everything a specialty trade sub needs to know about construction scheduling, from reading the CPM to protecting yourself on delay claims. Written from the sub's chair, not the GC's.

Bottom Line

If you can't read the schedule, you can't defend your position when things go sideways. And they always go sideways.

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Table of Contents

1. Reading a CPM Schedule
2. Understanding Float
3. Look-Ahead Schedules
4. Delay Documentation from the Sub's Perspective
5. Schedule of Values Strategy
6. Front-Loading
7. Acceleration
8. Schedule Updates and Recovery Schedules

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Reading a CPM Schedule

What Is CPM?

CPM — Critical Path Method — is a scheduling technique that maps every activity on the project, links them together with logical relationships, and calculates the longest path through the network. That longest path is the critical path, and it dictates the project completion date.

As a sub, you don't need to build the CPM. But you absolutely need to read it. The GC's scheduler built it, the owner's consultant reviews it, and your activities are buried somewhere inside it. If you can't find your work and understand how it connects to the rest of the project, you've already lost leverage.

How to Read a Gantt Chart

Most CPM schedules are displayed as Gantt charts — horizontal bar charts with time on the x-axis and activities listed vertically.

Element	What It Means
Bars	Duration of an activity. Longer bar = longer duration.
Diamonds	Milestones — zero-duration markers for key dates (substantial completion, inspections, owner deadlines).
Red/orange bars	Typically critical path activities — zero float.
Blue/green bars	Non-critical activities — they have float.
Arrows/lines between bars	Logic ties (dependencies) connecting activities.
Dashed lines	Often represent the data date or progress line.
Percent-complete shading	Filled portion of the bar shows how much work is done.

Predecessors and Successors

Every activity in a CPM schedule is linked to at least one other activity through a logic tie:

• Predecessor: The activity that must happen before yours can start (or finish).
• Successor: The activity that depends on yours being done.

The four relationship types:

Type	Abbreviation	Meaning	Example
Finish-to-Start	FS	A must finish before B starts	Rough-in before drywall
Start-to-Start	SS	A must start before B starts	Ductwork and piping starting together
Finish-to-Finish	FF	A must finish before B finishes	Commissioning finishes with testing
Start-to-Finish	SF	A must start before B finishes	Extremely rare — almost never used

Lags and leads: A relationship can have a lag (delay) or lead (overlap). An FS+5d relationship means the successor starts 5 days after the predecessor finishes. Watch for negative lags (leads) — they compress the schedule and may mean the GC expects you to overlap work that shouldn't overlap.

P6 vs. MS Project vs. Asta Powerproject

Software	Common On	What You'll See
Oracle Primavera P6	Large commercial, heavy civil, federal	Industry standard. Outputs to PDF or XER files. Complex.
Microsoft Project	Small-to-mid commercial, TI work	Simpler. GCs email you .mpp or PDF exports.
Asta Powerproject	Some international GCs, specialty firms	Less common in the US. Similar output.

You'll almost never open the native file yourself. You'll get a PDF printout, a Bluebeam session, or a view in a project management platform. What matters is that you can read the bars, find your activities, and trace the logic. Don't let the software intimidate you — the concepts are the same across all three.

Why You Can't Just Ignore the Schedule

Here's what happens when subs don't read the schedule:

• You show up and the area isn't ready. You eat the mobilization cost.
• The GC compresses your duration in an update and you don't catch it until you're behind.
• You miss a contractual milestone and the liquidated damages clause kicks in.
• You can't prove a delay claim because you never tracked your planned dates versus actual.
• Another trade stacks on top of you because the schedule said you'd be done — and you didn't object.

Sub's Rule

Get a copy of the baseline schedule at project start. Save it. Compare every update against it. That baseline is your anchor in any dispute.

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Understanding Float

Total Float vs. Free Float

Total float is the amount of time an activity can slip without delaying the project completion date. Free float is the amount of time an activity can slip without delaying any successor activity.

Example: You have a 10-day activity to install VAV boxes on the 3rd floor. It's scheduled to start June 1 and finish June 14. The next activity (duct insulation by another sub) doesn't start until June 28. Your total float might be 10 days. Your free float is also 10 days if there's nothing else constrained by your finish.

Now imagine an owner milestone on July 15 that the critical path passes through. If activities between you and that milestone eat up the slack, your total float could be different from your free float.

Why Float Matters to Subs

Float is your breathing room. When you have float:

• You can absorb minor delays without consequences.
• You have flexibility on crew scheduling.
• You're not on the critical path (usually a good place to be).

When float hits zero, you're critical. Every day you slip, the project slips. That's when the phone calls start and the GC's PM is in your trailer asking about manpower.

Who "Owns" the Float?

This is one of the most fought-over questions in construction scheduling. There are three positions:

1. The project owns the float — Most common contractual language. First party to use it gets it.
2. The GC owns the float — Some GC contracts include language giving the GC exclusive use of float. Read your subcontract.
3. The sub owns the float — Almost never recognized contractually, but you should argue for it on your activities.

Trap to Watch For

Many subcontracts contain a clause that says something like: "Subcontractor shall not be entitled to a time extension unless Subcontractor's work is on the critical path." This effectively lets the GC consume all your float with their own delays and then hold you to the original dates. Flag this clause during contract review.

How GCs Use Float Against Subs

Common tactics:

• Resequencing your work in a schedule update to consume your float, then claiming you're critical when you slip.
• Adding GC-controlled activities (inspections, coordination) as predecessors to your work, eating float.
• Issuing schedule updates that shift your activities earlier without a corresponding change order, creating a de facto acceleration.
• Batching updates quarterly instead of monthly so float erosion is hidden until it's severe.

Float Erosion

Float erodes throughout a project. A healthy 15 days of float at month 2 can become zero by month 6, even if you've done nothing wrong. Other trades slip, the GC adds logic ties, and the owner adds scope — all of it eats float.

Track your float monthly. When you see it dropping, send a letter: "We note that our total float has decreased from 15 days to 3 days between the July and September updates. This erosion is not caused by [your company]. We reserve all rights to time extensions should our work become critical due to delays by others."

Negative Float

Negative float means the project (or a milestone) is already projected to finish late. If you see negative float on your activities:

• The project is behind schedule.
• Someone is going to be asked to accelerate — possibly you.
• The GC may issue a recovery schedule.
• Do not ignore it. Document your position immediately.

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Look-Ahead Schedules

2-Week and 3-Week Look-Aheads

The master schedule is a strategic tool. The look-ahead is tactical. Most GCs issue a 3-week look-ahead (sometimes 2-week) at every weekly coordination meeting. It shows:

• What activities should start and finish in the next 2-3 weeks
• Crew and area assignments
• Material delivery dates
• Inspection dates
• Constraints (permits, RFIs, submittals not yet approved)

What to Watch For

Review every look-ahead your GC issues. Specifically check:

1. Your activity durations — Did they shorten your duration from the baseline? A task that was 10 days is now showing as 7 days. That's a red flag.
2. Start dates that moved up — If your start moved earlier without your agreement, that's a directed acceleration. Push back in writing.
3. Missing predecessors — If the look-ahead shows your work starting but the area isn't going to be ready (ceiling grid not in, walls not framed), raise it now. Don't wait until you show up with a crew and can't work.
4. Overlapping trades — If three trades are shown in the same area during the same week, it's going to be a mess. Raise the stacking issue.
5. Inspection holds — If an inspection is required before you can start and it's not shown, flag it.

How to Flag Unrealistic Durations

When the look-ahead shows durations you can't hit:

1. Mark up the look-ahead with your realistic durations.
2. Send it back in writing: "We reviewed the 3-week look-ahead dated [date]. Activity [name] shows a duration of 5 days. Based on our crew size of [X] workers and the scope of work in this area, a realistic duration is 8 days. Please revise."
3. Attend the coordination meeting and state it verbally — but always follow up in writing.
4. If they don't revise it, send a CYA letter confirming you raised the issue and the GC proceeded with the unrealistic duration.

Pull Planning and Last Planner System

Pull planning is a collaborative scheduling technique where the team works backward from a milestone to define what needs to happen, in what order, by whom. Instead of the GC pushing a schedule down, the trades pull the schedule by committing to what they can reliably deliver.

Last Planner System (LPS) basics:

• The "last planner" is the foreman or superintendent who actually directs the work — not the PM sitting in the office.
• Each week, you make commitments: "We will complete [task] by [date]."
• Commitments are tracked. Percent Plan Complete (PPC) measures reliability.
• When a commitment fails, the team identifies the root cause and addresses it.

If your GC uses pull planning, take it seriously. It's one of the few scheduling processes that actually gives subs a voice. Show up prepared, make honest commitments, and track your own PPC.

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Delay Documentation from the Sub's Perspective

Types of Delays

Delay Type	Who Caused It	Time Extension?	Delay Damages?
Excusable, Compensable	Owner or GC	Yes	Yes
Excusable, Non-Compensable	Force majeure, weather	Yes	No
Non-Excusable	You (the sub)	No	No (and you may owe LDs)
Concurrent	Both parties	Depends on jurisdiction	Usually no

How to Document Delays Daily

Your daily report is your most important scheduling defense document. Every single day, document:

• Crew size and hours: How many workers, what shift, actual hours worked.
• Work performed: Specific areas and tasks completed. "Installed 12 VAV boxes in rooms 301-312" is useful. "Worked on 3rd floor" is not.
• Delays encountered: Be specific. "Could not access rooms 315-320 due to drywall framing incomplete by [GC/other sub name]." Include the impact: "Lost 4 man-hours waiting for area."
• Weather conditions: Temperature, precipitation, wind. Note if weather stopped or slowed work.
• Material deliveries: What arrived, what's late, what's damaged.
• Visitors and directions: Note any verbal directions from the GC superintendent, owner's rep, or inspector. "GC superintendent Jones directed us to move to 4th floor and return to 3rd floor next week."

Documentation Standard

Write your daily reports as if a lawyer will read them in three years. Because they might. Stick to facts. Skip opinions. Be specific about who, what, where, when, and how long.

Time Impact Analysis Basics

A Time Impact Analysis (TIA) is a schedule analysis technique that demonstrates how a specific delay event affected the project completion date. It works by:

1. Taking a snapshot of the schedule just before the delay event.
2. Inserting a "fragnet" (fragment network) representing the delay.
3. Running the CPM calculation to see if the completion date moves.
4. The difference in completion dates is the delay impact.

As a sub, you probably won't build TIAs yourself. But you need to understand them because:

• Your delay claim will be evaluated using one.
• The GC will present their own TIA that minimizes your claim. You need to be able to challenge it.
• Having good daily documentation feeds directly into a credible TIA.

Notice Requirements

Almost every subcontract has a notice requirement for delays. Common requirements:

• Written notice within 48 hours or 72 hours of the delay event.
• Notice must identify the cause of the delay and the anticipated impact.
• Failure to give timely notice can waive your right to a time extension and delay damages.

Set up a system. The moment a delay occurs, your foreman should notify the PM. The PM sends written notice the same day or next day. Don't wait until the weekly meeting. Don't assume the GC knows about it. Put it in writing.

Delay Letters

A delay notice letter should include:

1. Date and project reference
2. Contract and subcontract reference
3. Description of the delay event — What happened, when it started.
4. Cause of the delay — Who is responsible.
5. Impact on your work — What activities are affected, crew impacts, out-of-sequence work.
6. Anticipated duration of delay — Best estimate.
7. Reservation of rights — "We reserve all rights to time extensions and delay damages per [contract section]."
8. Request for direction — "Please advise how you wish us to proceed."

Send it via the contractually required method (usually email with a copy to the project correspondence log). Keep a log of all delay notices with dates and responses.

Protecting Your Rights

Three things that kill delay claims:

1. No contemporaneous documentation. If you didn't document it at the time, it didn't happen.
2. Late or missing notice. Courts and arbitrators enforce notice provisions. "But they knew about it" is not a defense.
3. Continued performance without reservation. If you just keep working through a delay without objecting, you may waive your claim. Always reserve your rights in writing.

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Schedule of Values Strategy

What Is the SOV?

The Schedule of Values is your payment blueprint. It breaks your contract amount into line items that you bill against each month. A well-structured SOV improves your cash flow. A poorly structured one means you're financing the GC's project.

How to Structure SOV for Cash Flow

Think of your SOV as a cash flow tool, not just a billing requirement. Principles:

1. Break work into phases that match the construction sequence. If the project goes floor-by-floor, your SOV should too. This lets you bill as each floor completes, not at the end.

2. Separate material from labor. If you're procuring expensive equipment (rooftop units, switchgear, transformers), make those separate line items. You can bill for stored materials before installation.

3. Include mobilization. A mobilization line item (typically 3-5% of contract) lets you bill at the start of the project to cover your startup costs: trailers, tools, initial manpower, shop drawings.

4. Add submittals and shop drawings as a line item. Engineering and coordination work happens early. Get paid for it early.

5. Include demobilization. A small line item (1-2%) for demobilization at the end covers your closeout costs.

Mobilization and Material Storage Line Items

Mobilization: Bill it on your first pay application. It covers the real cost of getting set up on site. Most GCs will accept 3-5% for mobilization. Some contracts cap it or disallow it — read the subcontract.

Material stored: If you're procuring equipment weeks or months before installation, add line items for "Material Stored" by equipment type. Bill when the material hits the job site (or a bonded warehouse). You'll typically need:

• Proof of delivery (bill of lading, delivery ticket)
• Proof of storage (photos, warehouse receipt)
• Insurance certificate covering stored materials
• Transfer of title documentation (sometimes required)

Balancing SOV Across the Project

The goal is a billing curve that keeps you cash-positive throughout the project, not just at the end. Avoid:

• Back-loading: Putting too much value at the end. You'll finance the project for months and chase final payment.
• Extreme front-loading: Billing more than the value of installed work. The GC will reject pay apps and you'll lose credibility.
• Lumping: One line item for $2M of work. You can't bill partial completion easily. Break it up.

A good test: At any point during the project, the percentage billed should roughly match the percentage of work installed, plus a small margin for early-phase items (mobilization, submittals, stored materials).

GC Pushback

If the GC rejects your SOV, negotiate — don't just accept their version. Their version will be back-loaded to protect their cash flow at the expense of yours. Come prepared with a rationale for each line item value.

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Front-Loading

What Is Front-Loading?

Front-loading is the practice of assigning higher dollar values to early-phase SOV line items so you bill more money in the first few months of the project. It's not fraud — it's a cash flow strategy. But there's a line between smart billing and over-billing.

Why Subs Do It

• Cash flow: Subcontracting is a cash-intensive business. You're paying labor weekly, materials on 30-day terms, and getting paid by the GC on 60-90 day cycles. Front-loading bridges that gap.
• Risk mitigation: If the project goes sideways or the GC has payment problems, you've already collected more than you would under a perfectly linear billing curve.
• Retainage recovery: With 5-10% retainage held, you're already behind on cash flow. Front-loading partially offsets retainage drag.

How Much Is Too Much?

Rules of thumb:

Front-Loading Level	Risk Level	GC Reaction
5-10% ahead of installed value	Low	Usually accepted
10-20% ahead	Moderate	May get questions
20%+ ahead	High	SOV rejected or pay app reduced

The AIA G702/G703 pay application format includes a column for "% Complete" — the GC's PM and the owner's rep will compare your billed percentage to what they see installed on site. If you're billing 40% complete and the work looks 20% complete, expect a pencil reduction.

Risk of Over-Billing

If you over-bill significantly and then the project is terminated or you're removed:

• The GC will calculate the value of installed work.
• If you've been paid more than the installed value, they'll claim an overpayment.
• Your retainage may not cover the difference.
• In a dispute, over-billing weakens your credibility on every other claim.

Balancing Front-Loading with Project Phases

The safest way to front-load is to assign realistic but favorable values to early activities:

• Submittals and engineering: Value these at 8-12% of contract. The actual cost of engineering may be lower, but the argument that "engineering drives the project" is defensible.
• Mobilization: 3-5% is standard and rarely questioned.
• Rough-in phases: Value rough-in slightly higher than trim/finish. More labor-intensive work happens during rough-in.
• Testing and commissioning: Keep these values low. They happen at the end, and you want minimal dollars at risk during closeout when the GC holds all the leverage.

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Acceleration

Directed vs. Constructive Acceleration

Directed acceleration is when the GC (or owner) explicitly tells you to speed up. They issue a directive: "Complete the 3rd floor mechanical rough-in by March 15 instead of April 1." This is straightforward — you accelerate, you track costs, you submit a change order.

Constructive acceleration is more dangerous and more common. It happens when:

1. You experience an excusable delay (not your fault).
2. You request a time extension.
3. The GC denies or ignores the request.
4. The GC insists you meet the original completion date.
5. You're forced to accelerate to meet a deadline you should have been given more time to meet.

Constructive acceleration is recoverable — but only if you document it properly.

Documenting Acceleration

Whether directed or constructive, document everything:

• The directive or circumstances: Save the email, RFI response, meeting minutes, or verbal direction (confirmed in writing).
• Your acknowledgment with reservation: "We acknowledge your direction to accelerate. We reserve all rights to recover acceleration costs per [contract section]."
• Daily tracking of acceleration costs:
  • Overtime hours and premium rates
  • Additional crew members (names, classifications, hours)
  • Added equipment
  • Material expediting charges
  • Extended supervision
  • Lost productivity from crowding and stacking

Overtime Costs

Overtime is the most common acceleration method and the most expensive per unit of production.

Work Schedule	Labor Cost Premium	Productivity Loss (After Week 1)
5 x 10s	1.25x base rate	10-15%
6 x 10s	1.50x base rate	15-25%
7 x 10s	1.75x base rate	25-40%
Double shift	2.00x base rate	15-20% per shift

Productivity loss is cumulative. After 2-3 weeks of sustained overtime, your workers are fatigued, mistakes increase, rework goes up, and net production per dollar drops sharply. The mechanical contractors association (MCAA) and electrical contractors association (NECA) publish productivity loss studies — reference them in your acceleration cost claims.

Crew Stacking

Stacking means putting more workers in the same area than the space can efficiently support. It's an acceleration technique that has severe diminishing returns:

• Two crews in an area designed for one don't produce double the output — they produce maybe 1.4x at best.
• Workers wait for tools, materials, and access.
• Safety incidents increase.
• Quality drops because supervision is spread thin.

If the GC directs stacking, document the crew counts by area with photos. Track productivity (units installed per man-hour) and compare to your baseline production rate. The delta is your stacking loss claim.

Calculating Acceleration Costs

Your acceleration cost claim should include:

1. Direct labor premium: Overtime hours x premium rate above straight time.
2. Productivity loss: Measured or estimated using industry studies (MCAA, NECA, BLS data).
3. Additional supervision: If you added a foreman or superintendent to manage the accelerated work.
4. Equipment: Added lifts, welding machines, etc.
5. Material expediting: Rush delivery charges, premium pricing for faster lead times.
6. Extended general conditions: If acceleration extends your overall presence on site.
7. Markup: Per your contract — typically 10% overhead and 10% profit on acceleration costs.

Notice Requirements for Acceleration

Before incurring acceleration costs, notify the GC:

"Per your directive dated [date] to complete [scope] by [accelerated date], we are implementing acceleration measures including overtime and additional manpower. We will track all acceleration costs and submit them as a change order. Our estimated acceleration cost is $[amount]. We reserve all rights under the contract."

If it's constructive acceleration, the letter is different:

"Our request for a [X]-day time extension dated [date] has been denied/not responded to. You continue to require completion by the original date of [date] despite the excusable delay described in our notice dated [date]. We are being constructively required to accelerate. We will track all acceleration costs and reserve all rights to recover them."

Critical Timing

Send the notice BEFORE you start accelerating. If you accelerate first and notify later, the GC will argue you voluntarily chose to work overtime.

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Schedule Updates and Recovery Schedules

How Schedule Updates Work

The GC (or their scheduler) issues schedule updates on a regular basis — typically monthly. Each update:

1. Progresses the schedule to the data date (usually the end of the prior month).
2. Actual start and finish dates are entered for activities that started or completed.
3. Remaining duration is updated for activities in progress.
4. New activities may be added (change order work, added scope).
5. Logic changes may be made (resequencing, new dependencies).
6. The CPM is recalculated, producing new early/late dates and float values.

What to Review in Every Update

When you receive a schedule update, check these items before the next coordination meeting:

1. Your activity dates: Did your start or finish dates change from the prior update? If so, why?
2. Your durations: Did the GC shorten any of your activity durations? This is a common and insidious tactic — they compress your duration to absorb delays elsewhere.
3. Your logic ties: Were new predecessors added to your activities? Were existing ties removed? Logic changes affect your float and sequencing.
4. Your float: Compare float values to the prior update. If your float decreased, understand why. If someone else's delay consumed your float, document it.
5. Critical path changes: Did any of your activities move onto the critical path? If so, you're now exposed to liquidated damages risk.
6. Out-of-sequence progress: Are activities shown as progressing out of the planned sequence? This can distort the CPM calculation.
7. Constraints: Were any constraints added to your activities (mandatory start/finish dates)? Artificial constraints can hide float and distort the schedule.

Monthly Discipline

Assign someone on your team to review every schedule update. Don't just file it. Compare it to the baseline and the prior update. If you find changes that affect your work, respond in writing within 7 days: "We have reviewed Schedule Update #[X] and note the following concerns..."

Recovery Schedules

A recovery schedule is requested when the project is behind schedule. The GC (or owner) will direct you to submit a plan showing how you'll get back on track. This typically involves:

• Increased manpower
• Extended work hours
• Resequencing of activities
• Additional equipment
• Weekend or shift work

Before you submit a recovery schedule, understand the implications:

• If you submit a recovery schedule showing overtime and added crews, you may be conceding that the delay is your responsibility.
• If the delay was caused by others, respond with: "The delay to our work is caused by [cause]. A recovery schedule by [your company] is not appropriate. We request a time extension of [X] days and reserve all rights."
• If you do need to recover your own delay, submit a realistic plan. Overpromising on recovery and then failing to deliver makes everything worse.

Fragnet Inserts

A fragnet (fragment network) is a small group of schedule activities that get inserted into the master schedule to represent a change, delay, or recovery plan. As a sub, you may be asked to provide:

• Fragnets for change order work (new activities, durations, and logic ties to existing work).
• Fragnets for delay events (showing the impact of a delay on your work and successors).
• Fragnets for recovery plans (showing how you'll accelerate or resequence).

When building a fragnet, include:

• Activity IDs that follow the schedule's coding structure
• Realistic durations based on your crew and production rates
• Logic ties to existing activities (identify specific predecessor and successor activity IDs)
• Resource loading if the schedule is resource-loaded
• A narrative explaining the fragnet and its basis

As-Built Schedule Documentation

The as-built schedule is the final record of when activities actually happened. It's critical for delay claims, dispute resolution, and lessons learned. To build a defensible as-built:

• Track actual start and finish dates for every activity, every day. Your daily reports are the primary source.
• Keep your own schedule markup. Don't rely solely on the GC's updates. Mark up a copy of the baseline schedule with actual dates using a different color.
• Photograph progress weekly. Date-stamped photos tied to specific schedule activities are powerful evidence.
• Save every schedule update the GC issues. Each update is a snapshot in time. The series of updates tells the story of the project.
• Maintain a delay log. A simple spreadsheet: date, delay event, cause, responsible party, duration, notice sent (Y/N), reference documents.

Don't Lose Your Records

Projects end, people change jobs, laptops get wiped. Archive your project schedule documentation on a company server or cloud storage at project completion. Delay claims and disputes can surface years after the project closes. If you can't produce your records, you can't prove your case.

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Key Takeaways

1. Read every schedule you receive. Baseline, updates, look-aheads — all of them.
2. Track your float. When it erodes, send a letter.
3. Document delays in real time. Daily reports, photos, notices.
4. Structure your SOV for cash flow. Don't let the GC back-load your billing.
5. Front-load intelligently. Stay within defensible limits.
6. Never accelerate without written notice and cost tracking.
7. Review every schedule update for changes to your dates, durations, and logic.
8. Archive everything. The project file you keep today wins the claim three years from now.