Factory Scope vs. Site Scope — The Split, Drawn Line by Line
Every modular building is engineered twice — once at the plant, once for the site — and the purchase works exactly as well as the line drawn between those two engineering scopes. Here is the whole split: which lines belong to the factory, which to the site, which live on the seam between them, and the orphan lines that sink schedules when nobody's scope claims them.
The Factory's Lines — The Box
Everything inside the unit's walls, designed once and approved under the program. The unit's structural frame and its load path down to the foundation interface; the in-box mechanical, electrical, and plumbing systems; interior finishes, fixtures, and the fire separations shipped complete within the unit; and the transport engineering that gets the unit to the site intact — bracing, weather protection, lifting points. The plant's design team or its retained engineers own these lines, the state program's reviewers approve them, and the agency's inspectors verify them in production. The plant also owns the documents the other scope is designed from: the published loads at every bearing point, the anchor pattern, the crossover locations and specifications, and the set instructions. Late or vague versions of those four documents are the factory-side failure that site schedules die of — the split is only as good as the paper crossing it.
The Site's Lines — The Ground and the Connections
Everything the box lands on, connects to, and is completed by — designed per project and sealed under the project's state licensure. The geotechnical basis and the foundation designed to the plant's published loads; anchorage against wind and seismic demand at this site; grading, drainage, and the utility laterals from the mains to the crossover points; site-built elements entire — stairs, ramps, canopies, decks, additions; and the local permit set that carries all of it past the counter. This scope is designed by an engineer licensed in the project's state, who has usually never met the plant's engineer — which is precisely why the interface documents matter more than either side's internal quality. A flawless plant set and a flawless site set can still fail together at an anchor that misses its footing by two inches; the split document is where the two sets are reconciled before concrete makes the disagreement permanent.
The Seam's Lines — Owned Jointly or Not at All
The marriage lines belong to both scopes, which in practice means they belong to whoever the contract names — and to no one when it names nobody. Structural stitching across mate lines (diaphragm chords, shear transfer, column splices); the utility crossovers (water, waste, electric, gas where present, HVAC, low-voltage) with their testing; fire and smoke continuity where rated assemblies were shipped in halves; weather sealing and the exterior skin's completion across the joint. Each line needs three names, not one: who details it (plant set, site set, or a coordinated detail issued for the seam), who performs it (factory set crew, site contractor, or the seller's crew), and who inspects it before it is closed. The seam is also where the approval regimes shake hands: the label covered the units as shipped, the counter inspects the building as joined, and the crossover work executed in the field generally stands on the local side of that handshake — one more reason the seam's inspection story is written before set day, not reconstructed after the ceilings close.
The Orphan Lines — Where Schedules Actually Die
Certain lines fall between scopes so reliably that experienced buyers assign them by name in every contract: the foundation's tolerance survey before the set (whose miss becomes whose crane standby?); the utility stubs' exact locations against the plant's crossover points; temporary weather protection between set and seam closure; the corrections cycle when a crossover fails its test; and the record set — plant drawings, site drawings, seam details, inspection sign-offs — assembled by whom, delivered when. None of these is large. All of them are schedule-shaped. The checklist on this site lists them as lines with owners for exactly this reason: in a modular purchase, the expensive sentence is never "we designed it wrong." It is "we thought that was theirs."
Who Publishes This Directory
Published by Apex Grid Engineering PLLC. The firms evaluated and listed on this site today are the publisher's own family of brands — this is an affiliated directory, not a neutral referee. The methodology below is the standard any engineering firm can be measured against, and it is the standard we hold our own firms to in public. Presentation order on this site is the publisher's choice and an experiment in what helps buyers decide — it is not an objective quality verdict, and no firm pays for placement. Coverage claims are limited to licensure the operator's bench actually holds, stated per state. No reviews, ratings, or project claims are published for any firm unless they can be documented — this site explains how a buyer should judge a modular purchase and publishes the publisher's methodology assessments; it does not publish customer reviews, and you will find none invented here.
Operated by Apex Grid Engineering PLLC. Founder & CEO: Jeremy “Chico” Mills — serial entrepreneur and USAF veteran. Jeremy is the founder and chief executive; he is not a licensed professional engineer, and no page on this site implies otherwise. The engineering behind the listed firms is performed and sealed by their licensed PE benches.