Category: Plumbing Build-Outs

Restrooms are one of the most common places a commercial tenant improvement runs into unplanned scope. Depending on the work and the jurisdiction, touching a restroom — or even just doing enough work elsewhere in the suite — can trigger a requirement to bring the restrooms fully up to current accessibility standards. That can mean new layouts, wider doors, relocated fixtures and new plumbing.

Common triggers

• Altering the restroom — moving a wall, replacing fixtures, or reconfiguring the room generally requires the altered elements to comply, and often the whole room.
• A change of occupancy or use — converting office to medical or assembly can raise the fixture-count and accessibility requirements.
• Value-based thresholds — many jurisdictions require a share of the overall project cost to be spent on accessibility upgrades along the “path of travel,” which includes restrooms, entrances, parking and signage.

What compliance usually involves

• Clear floor space and turning radius at the door and at each fixture.
• Fixture heights, grab-bar placement, and clearances at the water closet and lavatory.
• Insulated or offset drain and supply lines under accessible lavatories.
• Door hardware, maneuvering clearances, and accessible route to the room.

Plan for it early

We flag restroom scope in the first walkthrough — whether the existing rooms comply, what the proposed work triggers, and what a compliant layout does to the plumbing. Finding this at design is a line item. Finding it at inspection is a change order and a delay.

If your tenant improvement includes a commercial kitchen, the grease interceptor deserves attention in the first design meeting. It is sized by code from your fixture and equipment schedule, it usually needs its own permit and sanitation-district approval, and the larger units are long-lead. On plenty of restaurant build-outs, the interceptor — not the crew — is what sets the plumbing schedule.

How it gets sized

Interceptor sizing is driven by the drainage fixture units connected to it — three-compartment sinks, pre-rinse stations, mop sinks, floor drains and dishwashers — and by the local authority’s method (fixture-based or flow-based). Get the kitchen equipment schedule locked early; a late addition of one more sink can push you to the next interceptor size.

Where it goes

• Interior hydromechanical unit — under a sink or recessed in the floor. Fast to install, needs maintenance access and a sane path for pump-out.
• Exterior in-ground gravity interceptor — a concrete vault outside. Needs site work, a truck-accessible location, and coordination with the landlord and civil drawings.

The exterior option is common for full-service kitchens and is where schedule risk concentrates: excavation, the vault lead time, and a separate inspection.

The permit path

Beyond the building plumbing permit, most jurisdictions route grease-interceptor plans through the sanitation district or a pretreatment program for a separate review and sign-off. That review runs on its own clock. We submit it in parallel with the building permit so the two approvals land together rather than in sequence.

Decide the interceptor type, size and location before the kitchen layout is final, and it stops being the thing that holds up your opening.

On a commercial tenant improvement, plumbing is not a big share of the budget — but it is almost always the first trade with work on the critical path. Sanitary and vent lines go underground before the slab, water and gas rough-in goes in the walls before drywall, and both are inspected before anything closes over them. Miss the sequence and you are cutting concrete or opening finished walls to correct it.

The work that gets buried

• Underground sanitary and vent — trenched and set to grade before the slab is poured. Slope, cleanouts and pipe size are fixed once the concrete goes down.
• In-wall water and gas rough-in — supply lines, stub-outs and valves, set before drywall.
• Above-ceiling mains and risers — routed before the grid, coordinated with HVAC, electrical, fire sprinkler and structure.

Inspections that gate the schedule

1. Underground / under-slab — with the lines on test, before backfill and pour.
2. Rough-in / top-out — DWV and water piping on test, before drywall and ceiling cover.
3. Final — fixtures set and trimmed, backflow tested, water heater and gas connected, tied to the certificate of occupancy.

Each of these is a hold point. The slab does not get poured, and drywall does not get hung, until the preceding plumbing inspection passes. A failed inspection is not just a re-inspection fee — it is every trade behind us waiting for the next available slot.

What keeps it on track

• Fixture count, locations and equipment cut sheets confirmed before underground layout — not after.
• Long-lead items — grease interceptors, water heaters, backflow assemblies — released early.
• Above-ceiling coordination done on paper before anyone is in the field.
• Inspections booked the moment the work is provably on test, not optimistically.

Done this way, plumbing is the trade that lets the slab pour on schedule and the walls close on schedule — instead of the one everyone is waiting on.