Layouts
- single wall
- parallel
- L-shaped
- wet + dry zones
- compartmented
Rooms · Chapter 2
Bathrooms
A bathroom is more than tile and fittings. It's layout, measurements, water, drainage, waterproofing, air and light, all working together in a small, wet room.
2.1
The bathroom family tree
A bathroom is a combination of layout, measurements, services, materials and details that all have to work together, in the wettest room in the house.
Most bathroom failures are water you never see.
- 1Rain head
- 2Niche
- 3 panel
- 4Linear
- 5Flush plate
- 6Wall-hung
- 7
- 8Mirror
Functions
- bathing
- washing + grooming
- storage
- air + light
Services
- hot + cold supply
- + traps
- electrical + lighting
- water heater
Fixtures
- + vanity
- shower
- tub
- + faucets
- accessories
Materials
- tile
- stone
- paint
- moisture-resistant wood
- metal
Maintenance
- easy-clean surfaces
- that slope right
- a that runs
- access for repairs
Comfortable dimensions make a big difference in everyday use
- height about 32–36″
- seat height 15–19″
- shower head about 80″
- 30″ clear in front of fixtures
Plan the hidden parts first.
2.2
Which bathroom layout works?
The right layout depends on the space, how many people use it and what functions you need. These are the common ones and when they work best.
Put the plumbing on as few walls as you can.
Single wall
- all fixtures share one plumbing wall
- cheapest to build
- works in long, narrow rooms
Classic 5 × 8 full bath
- the standard American hall bath
- 60″ tub/shower across the end
- and side by side
KEEP IN MINDTight but proven; follow the clearances.
Parallel
- fixtures on two facing walls
- good for medium rooms
- keeps wet and dry sides apart
L-shaped
- uses corners efficiently
- tucks the shower away
- small to medium rooms
Wet + dry zones
- shower behind or a wall
- the rest of the room stays dry
- easier to clean
Wet room
- whole floor and
- no curb, no door
Powder room (half bath)
- and only
- no shower, so less
- a place for a statement sink or mirror
Family bath
- built for several users
- double eases mornings
- more storage
Primary bath
- separate tub and shower
- often a private room
- feels open and calm
Two zones (recommended)
Keep the shower separate. The rest of the room stays dry, safer and easier to clean.
Compartmented
in its own room: 30 × 60″ minimum under the IPC (the IRC sets none), NKBA 36 × 66″.
Before choosing a layout
- where the existing and stack are
- the door swing
- window position for light and air
- who uses it, and when
- whether a tub matters for resale
Plumbing location drives cost more than size.
2.3
Bathroom dimensions you should know
Typical and recommended dimensions for comfortable use. Code is the minimum; NKBA is the better number. Actual sizes depend on the space, the users and accessibility needs.
Comfort lives in the extra few inches.
Around the toilet
Decide before rough-in- 15″ center to side (code), 18″ good
- 21″ in front (code), 30″ good
Sink + vanity
Decide before rough-in- center to side wall: 15″ code, 20″ good
- two : 30″ center to center minimum
- vanity height 32–36″ typical (NKBA: 32–43″)
- 21″ clear in front (code), 30″ good
Shower
Decide before framing- code: 900 sq in, no side under 30″
- good: 36 × 36″ or larger
- 24″ clear in front (code), 30″ good
Shower heights
Decide before rough-in- head about 80″ (custom for tall users)
- controls 38–48″ (NKBA)
Door
Decide before framing- 32″ door, more for accessibility
- swing clear of fixtures
- outward or pocket doors help small rooms
Movement space
- 30″ clear at each fixture
- 60″ circle for a wheelchair
Mirror
- center about 60–65″ off the floor
- bottom a few inches above the
Accessories
- paper holder: 26″ high, 8–12″ ahead of the bowl
- towel bar: about 42–48″
- robe hook: about 66–70″
Shower niche
Decide before framing- fits a stud bay: about 14½″ wide
- 12–24″ tall
- about 3½″ deep in a 2×4 wall
KEEP IN MIND it continuously and the sill toward the shower.
A quick ergonomic check
- fixture clearances met?
- door clears everything?
- enough room to dry off?
- controls reachable from outside the spray?
- grab-bar blocking in the walls?
- suits every user?
Use these numbers as a guide, not a rule.
2.4
Bathroom services and systems
A bathroom works when every service is planned together: water supply, drainage, waterproofing, ventilation, electrical, lighting and hot water. Each one hides in the walls, floor or ceiling.
Plan every service at the design stage.
- 1GFCI outlet
- 2Trap
- 3Shower
- 4
- 5 fan
- 6Duct to outside
- 7Vent
- 8 stack
Water supply
- ½″ lines to most fixtures
- ¾″ trunk lines
- 80 psi max static (code)
- a shutoff at every fixture
Drainage
- every fixture has a trap
- to the stack
- vented, so traps don't siphon
Waterproofing
- under tile in wet areas
- tile and grout are not waterproof
Ventilation
Decide before rough-in- fan: 50 CFM minimum (code, unless the room has 3 sq ft of window , half of it openable); a fan is always better
- ducted outdoors, never into the attic
- a timer or humidity sensor
Lighting + electrical
Decide before rough-in- GFCI on all bathroom outlets
- a 20 A circuit for bathroom outlets
- an outlet within 3 ft of each
- damp- or wet-rated lights near the shower
How water moves through a bathroom
- Street or well
- Main shutoff
- Water heater
- Hot + cold lines
- Fixture stops
- Fixtures
- Traps
- Drain + vent stack
Key points to remember
- plan all services at design
- coordinate plumbing, electrical and tile drawings
- use quality and fittings
- proper and access panels
- keep services in walls and ceilings
- follow local code and maker instructions
- test everything before closing up
A bathroom is a system, not a room.
2.5
Waterproofing in bathrooms
Waterproofing protects the structure from water damage. Tile and grout are not waterproofing; they're the finish. A real membrane, careful detailing and testing are essential in showers.
Tile is the finish. The membrane is the protection.
- 1
- 2Shower walls, full height
- 3Shower floor
- 4Shower
- 5Turned up all walls
- 6Whole floor
Where to waterproof
Decide before tile + floors- shower walls: full height (code: nonabsorbent finish to at least 6 ft)
- the entire shower floor
- tub walls with a shower head
Floor layers
- tile
- thinset
- mortar bed
- subfloor
Wall layers
- tile
- thinset
- cement or foam backer board
- studs
Critical details
- floor-to-wall corners
- pipe and penetrations
- connection
- niche, bench and curb
Liquid-applied
- painted on in coats
- seamless, good around details
- meets ANSI A118.10 when listed
Sheet membrane
- bonded with thinset
- consistent thickness
- pairs with matching
Traditional pan liner
- PVC or CPE liner over a pre-
- the old-school mud shower
- needs clear weep holes at the drain
Flood test
- plug the , fill toward the curb
- wait 24 hours, check below (code minimum is 15 minutes)
- before any tile goes down
Cement board ≠
It won't rot, but water passes through it. It still needs a membrane.
Grout ≠ a seal
Grout is porous. Sealer slows staining; it doesn't stop leaks.
Key points to remember
- the whole shower floor and walls
- the floor toward the drain
- use one system, start to finish
- seal every corner and penetration
- flood-test before tile
- hire an experienced installer
Test it before you tile it.
2.6
The plumbing behind the wall
A bathroom needs supply and drainage, with the right fittings and pipe sizes. Good plumbing gives steady pressure, easy maintenance and no leaks.
Every concealed valve needs a way back in.
- 1Shower head
- 2Shower
- 3Tub spout
- 4Tub
- 5Stop valves
- 6Drain arm
- 7Closet bend
- 8Stack + vent
Shower valve
- one mixes hot and cold
- pressure-balance or thermostatic
- prevents scalding when someone flushes
Concealed vs exposed
- concealed: the US norm, clean look
- exposed: clawfoot tubs, retrofits
KEEP IN MINDConcealed needs an access panel or careful planning.
PEX
- the most common new supply pipe
- flexible, fewer joints
- resists freezing damage
Copper
- proven, long-lasting
- rigid, soldered joints
- costs more than PEX
CPVC
- plastic, hot and cold rated
- solvent-welded joints
PVC / ABS drains
- plastic , waste and vent
- light and easy to work
KEEP IN MINDOlder homes have cast iron drains and galvanized supply; galvanized rusts from the inside.
Typical sizes in a house
| Pipe | Size | Serves |
|---|---|---|
| Supply to a fixture | ½″ | sinks, toilet, shower |
| Supply trunk | ¾″ | the bath group |
| Sink drain + trap | 1¼″ | bathroom sink |
| Tub drain + trap | 1½″ | bathtub |
| Shower drain + trap | 1½″ min (2″ typical) | shower |
| Toilet drain | 3″ | toilet |
Important points
- plan the layout before framing
- quality pipe and fittings
- good pressure, especially for showers
- access to and tanks
- test for leaks before closing walls
- coordinate with electrical, and tile
Plumb it once. Plumb it right.
2.7
Drainage, floor slope and traps
Proper drainage keeps a bathroom dry, hygienic and long-lasting. The shower floor slopes to the drain, and every fixture has the right trap.
Water only goes where the slope sends it.
Shower floor slope
Decide before tile + floors- ¼″ per foot minimum
- ½″ per foot maximum (code)
- use smaller tiles on a center
Point drain
- the most common
- works with small tiles
- four-way
Linear drain
- one-way , so large tiles work
- clean modern look
- good for curbless showers
Tile-insert drain
- blends into the floor
- minimal look
KEEP IN MINDPrecise installation; hard to service.
P-trap
- holds a water seal against sewer gas
- 2″ minimum seal
- on every , tub and shower
Curbless shower
- no step into the shower
- floor recessed or built up
- best for aging in place
KEEP IN MINDPlan at framing: the subfloor has to drop.
S-traps ≠ allowed
S-traps, drum traps and bell traps are prohibited in new US work. are the exception: their trap is built in.
No floor
Most US bathrooms have no floor drain outside the shower. A leak goes straight to the ceiling below.
Important notes
- the shower floor to the drain
- right trap size for each fixture
- every trap vented
- drain location set before tile layout
- no flat spots or back slopes
- access to clean the drain
Slope, trap, vent: in that order.
2.8
Tile and stone in a bathroom
Wet floors need grip, and showers need tile and stone that handle water. Tile types, stone and setting have their own chapter.
Wet floors need grip.
Where to use which
- shower walls: porcelain, glazed ceramic or sealed stone
- shower floor: mosaic or textured porcelain
- main floor: porcelain or stone, wet DCOF 0.42+
- accent wall: anything that suits dry areas
Tile in a bathroom
- porcelain or mosaic on wet floors
- glossy and tile on walls only
- epoxy or urethane grout in showers
Stone in a bathroom
- honed, leathered or flamed on floors
- polished on walls and tops only
- seal it; use gentle cleaners
Before you order
- slip rating on every floor tile
- tile size vs slope
- the right grout for wet areas
- seal natural stone
Glossy goes on the wall, never the shower floor.
2.9
Toilets and flushing systems
A toilet is more than the bowl you see: the flush, the installation and the water supply all affect performance and upkeep. It has its own chapter.
Toilets have their own chapter
- anatomy and every part
- types: two-piece, one-piece, wall-hung, upflush
- code vs good clearances
- rough-in and the flange
- costs and lifespans
2.10
Shower areas and fittings
The shower needs the right slope, waterproofing, drain and fittings to work well. The head, valve, enclosure and accessories decide comfort and upkeep.
Put the controls where you can reach them dry.
Wall-mounted head
- the most common
- easy to install
- many styles
Rain head
- a soft, overhead flow
- needs a ceiling or long arm
- best in larger showers
Hand shower
- flexible, great for cleaning
- helps kids and older users
- on a slide bar or holder
Body sprays
- spa feel
- needs volume and pressure
- larger showers
Shower valves
- code requires an anti-scald : pressure-balance, thermostatic or a combination
- limit stop set to 120°F max
Frameless glass
- clean, open look
- 3/8″ tempered is common
- makes the room feel bigger
KEEP IN MINDHeavier; needs solid blocking and good hardware.
Framed glass / curtain
- more affordable
- easier to install
- curtains suit tub-showers
Niche
- recessed niche: sizes on the dimensions spread
- keep it off the exterior wall
Bench
- 17–19″ high, about 15″ deep
- the top to drain
- great for shaving and aging in place
Grab bars
- install blocking now, bars later
- rated to carry body weight
- 33–36″ high is typical
Shower seals
- sweeps and seals stop leaks
- replace when they harden
Important points
- anti-slip tile on the floor
- to the drain
- every surface
- pick fittings for your water pressure
- plan niches and blocking early
- to stop mold
- or curtain to contain spray
A great shower is planned before the wall closes.
2.11
Comfort, air and extras
Small additions make a bathroom better every day. Most need power or blocking planned early.
The fan is the most important fixture you'll never look at.
Exhaust fan size
- code: 50 CFM minimum
- guideline: about 1 CFM per sq ft for rooms up to 100 sq ft
- a near the shower and in a room
Fan control
- humidity sensor switch
- timer that runs it after you leave
Heated floor
- electric mat under tile or stone
- its own circuit and thermostat
Towel warmer
- hardwired or plug-in
- blocking and power before tile
Mirrors + cabinets
- recessed medicine cabinets need a stud bay
- lit need a box behind
Bidet seat
- outlet beside the
- hot water line if the bidet needs it
Before drywall
- sized and ducted outside
- outlets for , , warmer
- blocking for everything
- heat mat circuit
Comfort is wired in.
2.12
Bathroom team, timeline and cost
A good bathroom is the result of a well-coordinated team. Each trade has a specific role, and the order of work matters.
Coordinate the trades, or pay for rework.
Designer / architect
- layout and space planning
- materials and fixtures
- coordinates the trades
General contractor
- schedules and manages the job
- demolition, framing, drywall
- pulls the permit
Plumber
- supply and
- and fixtures
- pressure and leak tests
Electrician
- , lights and outlets
- GFCI and circuits
- heated floors,
Tile setter
- and flood test
- tile, stone and grout
- and finish
Inspector
- rough plumbing and electrical
- shower pan, where required
- final sign-off
Ballpark cost, 2026 US (replace with your bids)
| Project | Range | Note |
|---|---|---|
| Powder room refresh | $5,000–15,000 | no shower, little plumbing |
| Hall bath, 5 × 8 full remodel | $15,000–35,000 | tub/shower, tile, vanity |
| Primary bath | $35,000–80,000+ | separate shower and tub |
| Contingency | 10–15% | always, in older homes more |
Typical order of work (full bath)
- Design + permit · 2–4 wks
- Demo + framing · 2–5 days
- Rough plumbing + electrical · 1 wk
- Inspection
- Waterproofing + flood test · 2–4 days
- Tile · 1–2 wks
- Fixtures + trim · 3–5 days
- Final inspection
Important points
- work with licensed trades
- finalize every spec before demo
- with a warranty
- pull the permit
- plan the slope
- budget a contingency
- walk the final for leaks and finish
The best bathrooms are planned twice and built once.