How Drawing Review Caught $375K in Clashes at a Pennsylvania Plant

A Bridge Crane, Rack Storage, and Joists Carrying $375,000 in Conflicts

A general contractor was preparing to build a manufacturing facility in Pennsylvania. The plant had a production bay with an overhead bridge crane, high-piled rack storage under ESFR sprinklers, process piping, heavy rooftop equipment, and a row of loading docks. The drawing set ran 1,200 pages.

Every one of those systems depends on another discipline's sheets. The crane lives on the structural and equipment sheets, so the mechanical and fire protection engineers rarely look at it. The sprinkler design was delegated and issued later than the rest of the set.

On a plant, each of those gaps shows up after the steel, the duct, or the pipe is already hung. The contractor wanted them on paper before buyout.

Helonic Found $160,000 in ESFR Obstructions and $80,000 Under the Crane

The contractor uploaded the full 1,200-page PDF set and specifications. Helonic compared the crane, joist, and roof framing data on the structural sheets with the mechanical, plumbing, fire protection, and electrical layouts, and checked each against the specs and the governing codes.

The most expensive finding was ESFR sprinkler obstructions. The spec called for ESFR heads over rack storage. NFPA 13 requires added sprinklers below obstructions wider than 24 inches, and the mechanical plans ran wide rectangular ducts across the storage area at deflector level, with cable tray beside them. The sprinkler drawings showed no heads below either one, and the rack heights on the equipment plan went past the sprinkler design basis. The contractor priced the field fix at about $160,000.

The second was the bridge crane envelope. The crane data required clear space above the rail for the bridge and trolley. The main supply duct and a sprinkler main both crossed the bay below that line. Helonic flagged it in the first pass. Rerouting the duct trunk after it is hung was estimated at about $80,000.

The third was process piping hung at joist midspan. The structural notes allowed concentrated loads only at joist panel points, and the hanger spec said the same. The plans hung a chilled water main and a compressed air header on trapezes at a spacing that landed at midspan on most joists, with each hanger carrying a few hundred pounds. That meant joist reinforcement or a new support frame, an RFI, and a structural review cycle, about $60,000.

The fourth was rooftop equipment on standard joists. A heavy rooftop unit sat with its curb straddling a joist line, with no dunnage or special-design joists on the roof framing plan. A duct curb opening also cut through a joist. The contractor put that at about $50,000.

The fifth was piping in the electrical room. NEC 110.26(E) keeps the dedicated space above switchgear, panelboards, and MCCs clear of foreign piping. The plumbing plans ran a roof drain leader and a domestic water line across the room that held the main switchboard and the MCC lineup. Storm piping runs by gravity and is hard to move after rough-in, about $25,000.

The sixth repeated at every dock. A unit heater, its flue, a light fixture, and conduit sat in the high-lift track zone of the overhead doors. The contractor priced each door at about $3,000 to relocate after install.

See how to review construction drawings, AI for construction drawings, 2D clash detection, bay area mixed-use drawing review, phoenix hospital drawing review, and portland apartment drawing review.

More Than $375,000 in Rework Moved Into the Drawings

The contractor sent all six findings to the design team as RFIs, each with the sheets and the conflicting values marked.

The duct and sprinkler main were raised out of the crane envelope or rerouted around the bay. The process piping hangers moved to joist panel points. The roof framing picked up dunnage and reinforced joists under the rooftop unit.

The storm and water lines were rerouted around the electrical room. The sprinkler designer added heads below the wide ducts and tray, and the design basis was reconciled with the rack heights. The dock equipment moved out of the door tracks.

Together, the six findings came to more than $375,000 in field rework kept on paper: $160,000 for the ESFR obstructions, $80,000 for the crane envelope, $60,000 for the joist hangers, $50,000 for the rooftop unit, $25,000 for the electrical room, and $3,000 for each dock door.

“Our 42-inch supply duct was drawn right through the crane envelope, and the sprinkler main was even lower. Nobody had caught it because the crane only lived on the structural sheets. Helonic found it in the first pass. That's a reroute we would have done after everything was already hung.”

Frequently asked questions