Describe the room you actually have
A 5 × 8 ft rectangle contains 40 sq ft, approximately 3.72 m². That describes the footprint, not the amount of work. Record the ceiling height, door swing, window, tub or shower, toilet and vanity. Note which walls and finishes will remain and whether another bathroom is available during construction.
Give bidders a measured sketch and a list of products or selection allowances. Explain whether the existing tub stays, the bathing area is rebuilt, or the room becomes a shower-only bathroom. Keeping fixtures in the same places can avoid some relocation work, but it does not establish that the existing drains, wiring, ventilation or substrate are suitable for the new installation.
Read national spending figures with their definitions
The 2026 Houzz Bathroom Trends Study reports a 2025 median of $18,000 for major remodels of bathrooms under 100 sq ft. Its spending pages draw on the separate Houzz & Home Study; the bathroom-features survey of 1,619 Houzz users is a different sample. “Major” in that report means at least the shower was upgraded. These are historical participant results, not October 2026 bids for a 40 sq ft room.
Use that distinction when comparing an online number with your proposal. A project replacing a vanity and painting walls cannot be compared directly with one opening the bathing area and renewing the waterproofing. Ask which operations, products, taxes and owner expenses are included before deciding whether an offer fits your needs.
Request a complete room rather than a tile price
| Part of the job | What the proposal should explain |
|---|---|
| Protection and removal | Access route, dust separation, removed items and disposal |
| Plumbing | Fixtures retained or moved, connections, valves, drain assessment and tests |
| Electrical and exhaust | Lighting, receptacles, fan, duct route and required inspections |
| Substrate and water management | Condition assessment, preparation and compatible bathing-area assembly |
| Finishes and handover | Tile extents, paint, trim, sealants, cleanup and operating checks |
A fan that makes noise is not proof that moist air leaves the building. The DOE/PNNL bathroom fan guide calls for exhaust outdoors, rather than into an attic or concealed space. Ask the installer to confirm the duct route and performance appropriate to the project. A new decorative grille alone does not resolve a disconnected or unsuitable duct.
A worked budget for one defined scope
| Item | Amount |
|---|---|
| Design, measurement and defined checks | 900 |
| Protection, demolition and disposal | 1,650 |
| Defined plumbing work and connections | 3,600 |
| Electrical work and exhaust package | 2,100 |
| Subfloor, backing and substrate preparation | 2,400 |
| Bathing-area waterproofing, surround and tile work | 4,800 |
| Tub, vanity, toilet and selected fittings | 3,300 |
| Painting, trim and final cleanup | 1,250 |
| Work and products subtotal | 20,000 |
| Permit allowance, final planning amount | 600 |
| Temporary household arrangements | 450 |
| Chosen contingency: 15% of work subtotal | 3,000 |
| Total funding for this example | 24,050 |
The $20,000 work subtotal becomes $24,050 after permits, household costs and contingency. The 15% reserve is an editorial choice for the example, not a required industry percentage. Known water damage belongs in a separately described and priced repair once investigated. A reserve does not make an excluded structural or remediation project part of the agreement.
Compare a layout change on the same basis
Suppose a second design adds a quoted $1,200 for drain relocation, $800 for rebuilding affected wall areas and $500 for additional finishing. These invented additions total $2,500 and do not overlap the original allowances. Work becomes $22,500. At the same chosen reserve rate, contingency becomes $3,375. Keeping the other two allowances unchanged gives $26,925: $2,875 above the first funding plan.
That comparison is useful only while its assumptions hold. If the new layout affects structure, access or permit charges, those differences need investigation and new prices too. Ask the designer and relevant trades to confirm workable clearances and service routes before treating the second drawing as buildable. The room’s small area does not waive local requirements.
Measure buying quantities separately
For a purchasing exercise, suppose the room is exactly 40 sq ft and a 2.5 × 5 ft tub occupies 12.5 sq ft. Assume the remaining 27.5 sq ft receives floor tile, including beneath a wall-hung vanity. Choosing a 12% cutting allowance gives 30.8 sq ft. With 10.5 sq ft per box, two boxes provide only 21 sq ft; three provide 31.5. The dimensions, packaging and cutting allowance are example assumptions, not a takeoff for every bathroom.
Wall tile, niches, returns, pattern alignment and the waterproofing system need their own takeoff. Confirm finished coverage with the installer before ordering. Record who buys each item and whether delivery, matching trim and replacement of damaged pieces are included. Do not add an owner-purchased vanity again inside a contractor’s fixture allowance.
Resolve local approvals and the start conditions
Seattle’s permit guidance illustrates why a room label is insufficient: construction and trade requirements depend on what changes. In Seattle, plumbing permits are administered through Public Health — Seattle & King County; that is a local example, not the arrangement for every U.S. city. Ask the authority for your property which permits and inspection stages apply.
Tax also needs a location and contract basis. California’s construction tax guidance distinguishes materials, fixtures and contract types; applying one sales-tax percentage to every U.S. remodel total would be misleading. In a pre-1978 home, discuss paint-disturbing work with an appropriately lead-safe contractor using EPA guidance before demolition.
- Approve the scope, selections and allowance basis.
- Confirm permits, responsibility for inspections and access to another bathroom.
- Check product availability and the contractor’s prerequisites before agreeing to demolition.
- Keep the current quote, approved changes and payments together.
- At the final walkthrough, review operation, visible finishes, inspection records and maintenance instructions.
Sources and scope
- Houzz Research — 2026 U.S. Bathroom Trends Study
- U.S. DOE / Pacific Northwest National Laboratory — Bathroom exhaust fans
- Seattle Department of Construction & Inspections — Do you need a permit?
- Public Health — Seattle & King County — Plumbing and gas piping permits
- California Department of Tax and Fee Administration — Construction contractors: industry topics
- U.S. Environmental Protection Agency — RRP program: consumers
Sources reviewed on 18 October 2026. Dollar amounts are USD. Worked budgets, reserves and scheduling examples are editorial illustrations, not local bids, national price averages or prescribed allowances. State and city examples are identified; requirements depend on the property, contract and jurisdiction.