Coffee Shop Tenant Improvement: What Must Be on the Plans Before You Issue the Permit
A permit application for a 2,400-square-foot coffee shop tenant improvement in a strip mall arrives with three sheets: a floor plan, a single-line plumbing riser, and a water heater cut sheet. The plan shows a hand sink, a prep sink, a three-compartment sink, a mop sink in a closet, two single-occupant restrooms, and one floor drain. The existing 4-inch building drain and 1-inch water service are marked "existing to remain." There is no fixture-unit calculation, no vent routing above the ceiling, no sewer-invert elevation, and no gas piping shown for a six-burner range and two ovens that the mechanical sheet lists at 320,000 Btu/h. The grease interceptor is noted as "50 GPM, sized by supplier." The contractor wants to begin under-slab work Monday.
1. Sort the missing information into (a) items that must appear on approved drawings before permit issuance and (b) items that may be accepted as deferred submittals. Justify each placement.
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Must be on the drawings before issuance - these are design-basis items the reviewer personally verifies:
- Fixture-unit / drainage load calculation and the resulting pipe sizes. Without it there is no way to confirm the 4-inch building drain can absorb the new load.
- Vent routing, including the stack through the roof, its size, termination, and any air admittance valves. A riser alone does not show trap-arm distances or vent connections.
- Sewer invert elevation. This determines whether the under-slab work needs a backwater device and whether the interceptor can drain by gravity.
- Gas piping layout and sizing for the 320,000 Btu/h connected load. Gas is a plan-review item, not a product to be deferred: the reviewer checks sizing method, developed length, sediment traps, shutoffs, and connector lengths. Concealing it under-slab without review is the exact failure the review exists to prevent.
- Water heater installation details - relief discharge route and termination, drain pan and drain, combustion air/venting, and expansion control. A cut sheet proves the product exists, not that it is installed legally.
Generally acceptable as deferred - the grease interceptor itself, as a listed manufactured unit sized by its manufacturer, provided the sizing data and the sewer-use authority's approval accompany it and the connecting piping is shown on the plan. Similarly, a listed fire-suppression hood system.
Rule of thumb: defer products and listed assemblies, never the sizing and routing logic of the system.
2. The designer argues that the grease interceptor is performance-specified and therefore needs no sizing data. How do you respond, and what do you require to close the item?
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Performance specification changes who does the sizing, not whether sizing exists. "50 GPM" is a flow rating of a box, not a statement that the box is adequate for this kitchen.
Require:
- The sizing calculation using a recognized method (fixture-capacity/retention-time or the manufacturer's published sizing for the fixture count), signed by the responsible designer.
- The discharge point of contact. The interceptor's acceptability is usually governed by the sewer-use authority or health agency, not the plumbing AHJ. Their approval, or a documented statement that none is required, closes the loop.
- Gravity drainage and venting of the interceptor, plus its accessibility for pumping and the two-compartment arrangement if required locally.
- The invert elevations proving the interceptor can be set below the fixtures and above the sewer.
If the provided calculation shows the 50 GPM unit is undersized for the connected fixtures, the item is a correction, not a deferral. State the deficiency in writing with the code section and the required resubmittal.
3. The contractor requests permission to rough in the restrooms and the under-slab drain while the gas piping is still being designed. What is your administrative response, and what conditions would you attach?
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A partial or phased permit is discretionary with the AHJ, not an entitlement. If you grant it, grant it explicitly and in writing:
- Define the approved phase by drawing, area, and system. Bathroom rough-in and vents may proceed only if the fixture-unit calculation and vent routing for those fixtures are already approved.
- Withhold the under-slab scope. The under-slab work includes the building drain and the interceptor location, both dependent on the open items (invert, interceptor sizing). Approving concrete-encasement work before those are resolved is how rework happens.
- Gas piping stays outside the approved scope and may not be concealed. Any installation performed outside the permit scope is subject to a stop-work order and removal.
- Tie the certificate of occupancy to the full scope. A phased permit does not create a phased occupancy.
- Confirm licensing and seals. Verify the plumbing contractor's license and that the drawings carry the seal required by state law for the project size.
Put all of this in an inspection record or correction notice so the file shows the conditions, not just the verbal approval.