Owner-Builder Basement Bath: What the Inspector Will Want to See
A homeowner in a Front Range Colorado town is finishing a basement and adds a bathroom with a water closet, lavatory, and a 36 by 60 inch shower. The house has a 4-inch cast-iron building drain under the slab and a 3-inch vent stack in an interior wall. The owner lives in the home and has pulled an owner-builder permit. He cut a wye into the building drain, ran 3-inch to the water closet, 1-1/2-inch to the lavatory, and 2-inch to the shower, laid at 1/8 inch per foot on the 3-inch and 1/4 inch per foot on the 2-inch. Because the ceiling below the stack is finished, he vented the lavatory with an air admittance valve inside the vanity cabinet instead of running a vent to the stack. He has already backfilled the slab patch and set the shower surround, and calls Friday afternoon for inspection because he wants to hang drywall Saturday.
1. What will the inspector expect to see at rough-in, and what happens to the drywall plan?
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Rough-in inspection is a before-concealment inspection. The drywall plan is the problem, not a scheduling detail.
What the inspector expects:
- All DWV and water piping exposed and complete to the point of connection, including the wye cut into the building drain, the slab penetration, and every joint that will be buried.
- A test of the DWV system - typically a water test to 10 ft of head, or, where the AHJ permits, a 5-psi air test held for the required period. The test must be witnessed.
- A test of the water distribution system at working pressure or higher for the specified duration.
- Venting complete - the inspector will follow the vent path to open air, and an AAV or a capped-off stub will stop the inspection there.
- Protection and support - pipe hangers, sleeving at the slab, and no pipe where a nail plate is needed.
Because the slab is already backfilled and the surround is set, the owner will likely be required to expose the concealed work before it can be approved. Drywall cannot go up first; if it does, the inspector can require it to come down. Advise the owner to call for the inspection with the work open, and to expect a re-inspection fee for the second trip.
2. Is the air admittance valve arrangement acceptable? What will the inspector likely require?
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Probably not as installed, and the reasoning is more important than the rule citation.
- An AAV is a vent of last resort, not a substitute for a vent system. It admits air but does not relieve positive pressure, so the drainage system still needs at least one vent to open air; here that exists via the 3-inch stack, which is a point in the owner's favor.
- The battery of fixtures matters. A water closet, lavatory, and shower in one bathroom are commonly wet-vented through the lavatory. Wet venting depends on a dry vent protecting the wet-vented branch. An AAV typically cannot serve as the dry vent at the head of a wet-vented group, so the inspector will likely require a real vent from the lavatory (or the group) to the stack. That is the finding that sinks the ceiling argument.
- Accessibility and listing. Where an AAV is permitted, it must be installed per its listing, remain accessible for replacement (the vanity cabinet counts only if it is not sealed shut), and be the correct size for the trap it serves.
- Slope is not the issue. One-eighth inch per foot is acceptable on 3-inch and larger drains, and 1/4 inch per foot on the 2-inch shower drain is correct - the owner got that part right.
The practical answer: cut the ceiling and run a vent, or create an accessible chase. Do not ask the inspector to bless a workaround that the drainage design does not support.
3. The homeowner's brother-in-law, an unlicensed handyman, offers to set the fixtures and make the final gas connection for cash. What are the permit and licensing issues?
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Several separate problems, and the plumber should say so clearly and in writing:
- The permit is an owner-builder permit. It allows the owner-occupant to do the work on his own single-family residence; it is not transferable to a hired helper. Once someone is paid to perform plumbing work, the work falls outside that exemption.
- Colorado licenses plumbers through the state plumbing board, and plumbing work for hire must be performed by or under the supervision of a licensed plumber working for a licensed contractor. Many jurisdictions also require a local registration on top of the state license.
- The permit must name who is doing the work. Changing from owner to contractor generally requires notifying the building department; the plumbing contractor typically pulls the permit for the work they perform.
- Gas work is not a handyman job. The final connection carries the same permit and inspection requirement as the rest of the work, and an unpermitted, uninspected gas connection is exactly the scenario that produces a CO or leak claim with an insurer who declines coverage.
- The final inspection will cover fixture setting, the gas connection, and the water heater if it is involved. Fixtures set before the final inspection should be accessible and correct - improper setting can force removal.
Frame the advice around the homeowner's exposure: unpermitted work discovered at resale, and insurance denial after a loss, is a far larger cost than the handyman's savings.