Bathrooms are small rooms with a lot of trades in them. That is what makes them easy to underbid: one missed line, such as the exhaust duct, the GFCI or the safety glass, and the margin is gone. The fix is to estimate the job as a checklist of line items, take off a quantity for each, and price each one for your market. Below is the checklist Ask Donnie's estimator works from, grouped by trade, with the code sections that add or shape lines.
Start with scope and the permit
Write down what is staying, what is moving and what is new before you count anything. Moving a toilet, a drain or a circuit changes the plumbing and electrical lines more than any finish choice does. Under the model IRC, altering a plumbing, mechanical or electrical system generally needs a permit (R105.1), and your local building department sets the actual list, so carry permit and inspection lines unless you have confirmed otherwise.
Demolition and prep
- Remove fixtures, tile, drywall and flooring in the scope.
- Protection for the floors and rooms you walk through.
- Debris loading and haul-off.
- An allowance or exclusion for what you may find behind the walls: rot, old wiring, failed subfloor.
Rough plumbing
- Supply lines (for example PEX) to each fixture, with shutoffs.
- Drain, waste and vent piping (for example PVC DWV).
- A trap for each fixture. The IRC requires every fixture to be separately trapped, within 24 inches vertically of the fixture outlet (P3201.6).
- Toilet flange, and relocation work if the layout moves.
- Shower valve and the shower pan or base.
Layout rules belong in the estimate, not just the plan. A toilet needs at least 15 inches from its centerline to any side wall, partition or vanity, and 30 inches center to center from an adjacent fixture (P2705.1). A shower needs at least 900 square inches of interior area with no dimension under 30 inches (P2708.1). If the existing room cannot meet those, the layout change becomes framing and plumbing lines.
Electrical and ventilation
- At least one receptacle within 36 inches of the outside edge of each sink basin (E3901.6).
- GFCI protection for the bathroom receptacles (E3902), by a GFCI device or breaker.
- The circuit feeding the bathroom, if the scope adds or replaces it.
- Lighting fixtures and switches.
- Exhaust fan rated at least 50 cfm intermittent or 20 cfm continuous (M1507.4), plus the duct run and the exterior termination. The exhaust has to go outdoors, not into the attic or a soffit.
Walls, floor and finishes
- Framing repairs, blocking for grab bars and accessories, and any wall changes.
- Backer board and waterproofing at the tub or shower.
- Drywall suited to a bathroom, taped and finished.
- Floor and wall tile, setting materials, grout and trim pieces.
- Paint.
Fixtures and glass
- Toilet.
- Vanity, top, lavatory sink and faucet.
- Tub, shower unit or tiled shower, and trim kit.
- Shower door or enclosure. Glazing in a tub or shower enclosure with its bottom edge less than 60 inches above the standing surface must be safety glazing (R308.4.5), and so must a window in that zone.
- Mirror, accessories and hardware.
Close out the number
- Permit, inspections and any plan fees.
- Cleanup and final punch list.
- Overhead and profit on top of the direct costs.
- Allowances for owner-selected finishes, stated as allowances.
- Exclusions, written down, so nobody assumes they were included.
Each line gets a quantity from your takeoff and a unit price for your market and your crew. A bid built this way can be read line by line, and if the owner changes a selection you can reprice that one line instead of the whole job. The code sections here follow the model IRC, and states and cities amend it, so confirm with your local building department before you finalize the scope.
The lines that sink a bathroom bid are the ones nobody sees at the walkthrough: the fan duct to the outside, the GFCI, the safety glass and the trap arm. Put them on the list every time.