Bathroom Layouts: Floor Plans for Powder, Hall and Primary Baths

A bathroom layout is mostly decided by things you cannot see: where the drain and vent run, which way the floor joists go, and how much room the code requires around each fixture. Get those right and the finishes are the easy part. This page walks through the common floor plans for powder rooms, hall baths and primary suites, and separates what Washington code requires from what designers recommend.

Start with the wet wall

The cheapest layout is usually the one that keeps the toilet, sink and tub or shower on their existing drains. Each fixture needs a drain sized for it, a trap, and a vent within a set distance, so moving a fixture means opening floors and walls to rebuild that path. Moving a sink a short distance along the same wall is often simple. Moving a toilet across the room is not, because its drain is large and needs a steady slope that the floor framing has to allow.

Before you draw anything, find out:

• Which wall carries the existing drain stack and vent, and whether it continues up from or down to another floor.
• Which way the floor joists run under the room, and whether the space below is a crawl space you can reach or a finished ceiling.
• Where the existing fan ducts out, and whether it reaches outdoors at all.

If the layout you want needs fixtures moved, read moving bathroom plumbing before you commit to it.

Code minimums versus designer guidelines

Washington uses the Uniform Plumbing Code with state amendments, and those amendments set the fixture spacing for a house. The National Kitchen & Bath Association (NKBA) publishes planning guidelines that ask for more room. The NKBA figures are recommendations, not code, and its own "code requirement" notes are based on the model International Residential Code plumbing chapters, which Washington does not use. The figures below are the ones that shape a floor plan.

The full plumbing rules, including the shower door opening and threshold, are on bathroom plumbing code in Washington. Washington's plumbing code also says grab bars and paper holders do not count as obstructions for clearance purposes.

Powder room layouts

A powder room holds a toilet and a sink and nothing else. There are two basic arrangements:

• Side by side on one wall. The toilet and sink share a wet wall, and the room only has to be wide enough for the toilet's side clearance, the sink and the gap between them. This suits a narrow room and keeps plumbing simple.
• Facing each other. The toilet and sink sit on opposite walls. The room has to fit both fixtures plus the clear space in front of each, which is where the 21-inch minimum and the 30-inch guideline matter most. It often needs a shallow vanity or a wall-hung sink.

Door swing is the usual problem in a powder room. If a swinging door would hit the toilet or sit in the clear space, a pocket door often solves it. More on these small rooms is on powder room remodels.

The 5 by 8 hall bath

The classic hall bath in tract houses of many eras is roughly five feet by eight feet. The standard plan puts a 5-foot alcove tub across the short end and the toilet and vanity side by side along one long wall, all on one wet wall. It works because every fixture shares the same plumbing run and the door opens onto the open floor between them.

Ways to improve it without moving the drain:

• Swap the tub for a walk-in shower on the same drain location. Washington allows a smaller drain in a tub-to-shower swap only in narrow conditions, with the building official's approval.
• Choose a shallower or wall-hung vanity to widen the walkway.
• Use glass instead of a curtain so the room reads as one space.

Where the room is truly tight, the ideas on small bathroom ideas show which changes gain real space.

Larger hall and family baths

A hall bath of 8 by 10 feet or so allows zoning: the vanity near the door, the toilet out of the direct sightline from the hallway, and the tub or shower at the far end. With the extra width you can fit two sinks, but check the NKBA's 36-inch centerline guideline and the space for an outlet within reach of each sink before you assume a double vanity fits.

Primary suite layouts

Primary bathrooms usually separate into three zones: a vanity zone, a wet zone with the shower and, if you keep one, the tub, and a toilet room or a toilet set behind a partial wall. Common patterns:

• Wet room. Shower and freestanding tub share one glassed, fully waterproofed area, with the vanity outside it. It is compact and visually open, but the whole wet area has to be built as a shower.
• Split plan. The vanities run along one wall and the shower and tub sit opposite, with the toilet in its own room at one end.
• Two vanities on separate walls. Each person gets a full vanity and mirror without sharing a counter.

Plan the fan, lights and outlets with the layout

Washington does not allow a window to substitute for a bathroom fan. Every bathroom and toilet room needs mechanical exhaust ducted outdoors, at 50 cfm intermittent or 20 cfm continuous. The Home Ventilating Institute suggests placing exhaust points over or near the shower or tub and in an enclosed toilet room, so a separate toilet room in a primary suite usually means a second fan or a second pickup. The code details are on bathroom ventilation code.

Lights and outlets follow the layout too. The electrical code requires a receptacle within 3 feet of each sink and keeps receptacles out of the tub and shower area, and Washington adds its own rules for light fixtures near tubs and showers. Those rules are on bathroom electrical code.

Seeing the layout before it is built

Floor plans are hard to read, and a few inches matter in a bathroom. At JDI Construction our bathroom designer, Denise Lacquement, plans the layout and prepares a 3D design layout so you can see the clearances, door swing and sightlines before anything is ordered. You can look at finished floor plans in our bathroom projects, read our earlier article on bathroom layouts, or start with bathroom remodeling in Vancouver, WA.