How Drawing Review Caught Plumbing Gaps on a Minneapolis Preschool

Child-Toilet Rough-In, Outdoor Air, and Floor Drains on 86 Sheets

A mechanical and plumbing engineering firm was sealing a one-story preschool in Minneapolis. The set was 86 sheets. Classrooms, a kitchen, and child toilets shared the same wing.

The plumbing rough-in for the child toilets landed inside the casework zone on the architectural elevations. The HVAC schedule listed outdoor air for the classrooms that did not match the diffuser callouts on the plan. Kitchen floor drains sat beside the equipment, not under the sinks the food-service plan showed.

Those three items are a field core, a rebalance, and a saw-cut slab if they wait until the toilets and the kitchen equipment are set.

Helonic Listed 214 Issues Before the Permit Submittal

They uploaded the permit PDFs. Helonic compared the toilet rough-in with the casework, the outdoor-air schedule with the classroom plan, and the floor drains with the kitchen equipment layout.

It listed 214 issues. The ones that repeated were the toilet rough-in inside the casework, the HVAC outdoor-air mismatch, and floor drains off the equipment plan.

The rough-in clash was the one that would have come back as a permit correction. The drains would have been a slab cut.

See school construction drawing review, Minnesota plan review requirements, plumbing coordination guide, how to respond to plan check comments, schedule verification, and the California K-12 review.

214 Issues, $90,000 Caught Before Permit

The engineers moved the toilet rough-in clear of the casework, matched the outdoor-air number to the plan, and shifted the floor drains under the sinks before issue.

They put the avoided field work at $90,000. That was core drilling the toilet wall and cutting the kitchen slab after the pour.

The building department commented on the kitchen hood make-up air. It did not comment on the rough-in or the floor drains.

The outdoor-air mismatch was a schedule that disagreed with the plan it described. Across 1,000+ drawing packages Helonic has reviewed, about 7 in 10 had at least one broken cross-reference, a callout pointing to a detail or sheet that does not match. See how much time construction teams lose searching for information.

Minnesota Plumbing Code, Ventilation Rules, and the $90,000 Caught Before Permit

Minneapolis enforces the Minnesota State Building Code, a statewide code that adopts the International Building Code with state amendments. Plumbing is governed by the Minnesota Plumbing Code, which is based on the Uniform Plumbing Code.

Classroom outdoor air is set under the Minnesota Mechanical Code and ventilation standards such as ASHRAE 62.1. The schedule number is what the balancer sets the system to. If the schedule and the diffuser callouts disagree, the system is balanced to one and inspected against the other.

Kitchen drains fall under the plumbing code and the health department's food service review. Food prep sinks usually drain through an indirect connection to a floor sink, which is why the drain has to sit where the equipment plan puts the sink.

Child toilets add another layer. Fixture heights and spacing for young children differ from adult fixtures, so the rough-in has to match the child-height layout on the architectural elevations and clear the casework.

“The toilet rough-in sat in the casework, the outdoor air did not match the schedule, and the floor drains missed the sinks. Helonic caught those on 86 sheets before we submitted.”

Minneapolis Preschool Drawing Review: Questions and Answers