Episode 163 of the Construction Accounting Podcast with George Ghazarian, CPA · 7 min 27 sec · Published 26 June 2026

You moved work offsite to get speed, quality and repeatability. The books never changed. They still look like a site-build project, and the margins they report are probably wrong.

Modular is construction plus manufacturing. This is how to structure cost codes, inventory, work in process and revenue recognition so a modular job tells you the truth while it is still running.

What you’ll learn

  • Why modular construction is really construction plus manufacturing
  • Where traditional job costing hides modular profit leaks
  • How to structure factory, logistics and field cost codes
  • When revenue recognition depends on transfer of control
  • How inventory and WIP accounts should handle finished modules

The Work Moves Before the Site Looks Busy

Traditional site-build accounting follows the jobsite. Materials show up at the property, labor works there, subs work there, and costs build as the building goes up. Modular breaks that mental model.

A large share of the work happens before the site looks busy at all. You can have hundreds of thousands of dollars of labor and material sitting inside a factory before a module ever touches the jobsite. Is that cost inventory? Contract work in progress? Job cost? Overhead? If you cannot answer that clearly, your job reports are not telling the truth.

Two Production Centers, One Cost Report

Normal job costing runs on a few basic buckets: labor, materials, subcontractors, equipment, overhead, change orders. Modular creates two production centers with completely different economics.

The factory has direct production labor, material issued from inventory, production supervisors, shop rent, utilities, forklifts, tooling, quality control, waste, rework and downtime. The field has foundations, site prep, transport, craning, setting, connections, MEP tie-ins, finishes and punch work. Smash all of that into one job-cost report and you cannot see where profit is made or lost. Maybe fabrication is profitable and install is killing you. Maybe install is clean and factory rework is destroying the margin. One gross margin number will never tell you which.

The Factory Is Not a Jobsite

A jobsite usually belongs to one project. A factory may support several at the same time. Crews move between modules, materials get bought in bulk, and supervisors oversee multiple production lines. That means manufacturing-style controls have to be layered into your construction accounting: bills of material, labor tracked by job and module and operation, inventory controls, a plant overhead rate and variance tracking — while you still carry construction WIP and revenue recognition on top.

Revenue Recognition Gets Harder, Not Easier

On a site build, progress is visible: foundation poured, framing up, rough-in done. In modular the building may be 60 percent complete inside a factory while the site still looks empty. So when do you recognize revenue?

That depends on the contract. Does the customer control the module while it is being built? Do you have an enforceable right to payment? Does title transfer during production, at shipment, at delivery, or after installation? Are you creating contract WIP, or building inventory you still control? Recognize too early and you overstate income. Recognize too late and profit looks worse than reality. Either way the owner makes decisions on bad numbers.

Stop Coding Material Straight to the Job

Buying material and immediately coding it to a job works on a site build, where it is delivered and installed quickly. In modular, material may sit in the plant, get used across several jobs, or go into a module that does not ship for weeks or months.

So separate raw material inventory, work in process, finished modules and job cost. Expense everything at purchase and profit gets crushed early and bounces back later, which makes the numbers useless for estimating, bonding, banking, tax planning and management decisions. Your books should show what happened, not just where the receipts landed.

A Five-Phase Cost Code Structure

  • Design, engineering and preconstruction
  • Factory production: direct labor, direct material, plant overhead, quality control, factory rework
  • Logistics: freight, escorts, permits, storage, cranes, rigging, insurance in transit
  • Site and installation: foundations, utilities, setting modules, structural tie-ins, MEP hookups, exterior closure, punch list
  • General conditions and project management

Build that structure before the job starts, not after. Keep factory labor separate from field labor instead of running one blended rate. Track material from purchase to inventory to WIP to installed cost. Build a plant overhead rate and apply it consistently, because rent, utilities, supervisors, equipment and quality control have to land somewhere — and if they do not land in job cost, every job looks more profitable than it really is.

What Bad Modular Accounting Actually Costs

Four things go wrong. You bid badly, because you do not know your real factory cost and you underprice the next job. You run short on cash, because billing milestones do not match factory cash outflows and you end up financing the customer’s project. Your margins lie, because overhead and rework were never assigned properly. And your tax and financial reporting cannot be trusted, which becomes a problem when a bank, a bonding company or the IRS starts asking questions.

Write contracts whose billing milestones, transfer of control, title, retainage and storage terms match the accounting. Then review modular WIP monthly. Not quarterly, not at tax time. Modular is not simpler accounting. It is more disciplined accounting, and where the discipline is missing, modular becomes a margin trap.

The short version

  • Modular creates two production centers: the factory and the field
  • Separate raw inventory, work in process, finished modules and job cost
  • Build a plant overhead rate or every job looks more profitable than it is
  • Never run one blended labor rate across factory and field work
  • Contract terms and transfer of control drive when modular revenue is recognized
  • Review modular WIP monthly, not quarterly and not at tax time

Want this applied to your numbers?

We are a CPA firm built for construction contractors. If you want to know what this looks like against your actual profit, salary and job mix, we will run it with you.

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This episode is general information about how these rules work, not advice for your situation. Tax law changes and the right answer depends on your entity, your income and your circumstances. Talk to a CPA before acting on it.