Here's a practical guide for single-user restrooms, built around the 2010 ADA Standards.
Recommended configurations
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Single wet wall, side-by-side (best baseline)
Toilet and lavatory both on the rear wall, door on the opposite wall. Roughly 7'-6" × 8'-0" with an in-swinging door. One plumbing wall, simple framing, and the easiest layout to keep compliant.
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Back-to-back mirrored pair (best when you need two or more rooms)
Two of Layout 1, flipped, sharing one plumbing chase. This is usually the lowest cost per room.
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Lavatory on the side wall (L-shape)
Toilet on the rear wall and the lavatory on the wall opposite the toilet's side wall. It fits a narrower, deeper footprint, around 6'-6" × 9'-0". It costs a little more because the lavatory branch turns the corner. It also needs care so that neither the lavatory nor the door swing intrudes on the 60" toilet clearance.
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Family/companion room
About 8'-0" × 10'-0" or larger, with a fold-down changing station and sometimes a second, child-height lavatory. Put it on the same wet wall or stack as the other restrooms.
ADA Clearance Requirements
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Toilet
Clearance around the water closet must be at least 60" measured perpendicular from the side wall and at least 56" measured perpendicular from the rear wall, and no other fixtures or obstructions may sit within it. That clearance may overlap the fixture itself, its grab bars, tissue dispensers, accessible routes, other fixtures' clear floor space, and the turning space. This is why the lavatory's 30×48 space can overlap, but the lavatory itself cannot.
Centerline 16–18" from the side wall.
Seat height is 17" min to 19" max, measured to the top of the seat.
The side grab bar is 42" long minimum, located no more than 12" from the rear wall, and extends at least 54" from the rear wall.
The rear grab bar is at least 36" long, extending at least 12" from the toilet centerline on one side and 24" on the other. The 24" extension goes toward the open side.
Both bars mount 33–36" above the floor to the top of the gripping surface. The gap between the wall and the grab bar is 1½".
Flush control goes on the open (transfer) side.
The toilet paper dispenser sits 7–9" in front of the bowl, with the outlet 15–48" above the floor.
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Lavatory and accessories
Rim no higher than 34". Knee clearance at least 27" high. Toe clearance at least 9" high. 30×48 forward approach.
Insulate or shield exposed hot water and drain pipes.
Faucets must work without tight grasping or twisting. Lever or sensor faucets both qualify.
Mirror over the lavatory: bottom of the reflecting surface no higher than 40".
Coat hook and dispensers within the 15–48" reach range.
Keep a 60" turning circle, or a T-turn within a 60" square. Knee space under the lavatory can count toward the turning space.
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Door
32" minimum clear width with the door open 90°, which means a 36" leaf in practice.
Pull-side maneuvering space (front approach): 60" deep, plus 18" beyond the latch.
Push-side maneuvering space: 48" deep, plus 12" beyond the latch if the door has both a closer and a latch.
The door may not swing into any fixture's clear floor space. Exception: in a single-user room, it can if a separate 30×48 space is provided beyond the arc of the door swing.
Hardware 34–48" above the floor and operable with one hand. The privacy lock must meet the same requirement.
Opening force no more than 5 lbf on interior doors. Threshold no more than ½". Closer takes at least 5 seconds to move from 90° to 12°. Smooth surface on the bottom 10" of the push side.
Additional Requirements in California
If the project is in California (CBC 11B): CBC 11B adds requirements beyond the ADA. It requires a 60"-wide by 48"-deep maneuvering space in front of the water closet, beyond the ADA clearance. A door may swing into that added space. It also narrows the toilet centerline to 17–18". If you design to 17½", the layout satisfies both standards.
Piping to Minimize Cost and Maximize Efficiency
The biggest cost lever is fixture adjacency. Every fixture on one wall, and every room on one chase or stack, means less piping and fewer penetrations.
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Layout and routing
Mirror rooms back to back and stack them floor to floor so they share one waste/vent stack and one supply riser. Locate the group near the building's main stack to keep slab trenching and horizontal runs short.
Wet-vent the toilet through the lavatory drain where your plumbing code allows it (IPC and UPC/CPC both do, with conditions). That can eliminate a separate toilet vent.
Keep trap arms within code length limits so you don't need extra vents. Put a cleanout at the end of each horizontal run.
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Fixture choices
Floor-mounted tank toilets cost the least. They need no carrier and fit a 2×6 wet wall, and they don't need the large supply line a flushometer does.
Wall-hung toilets need a carrier and a deeper chase of about 10–12". They cost more but clean easier, so they're worth it mainly in high-traffic public rooms.
Use a wall-hung lavatory with an offset grid drain or offset P-trap. This preserves the 27" knee clearance and makes pipe insulation simple.
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Water and energy
Keep hot-water developed length short; IPC caps it at about 50 ft. For a remote room, a point-of-use tankless or mini-tank heater is often cheaper than a long recirculation loop.
Public lavatories need tempered water through an ASSE 1070 mixing valve. Specify 0.5 gpm aerators and 1.28 gpf toilets; in California, CALGreen requires 1.28 gpf.
Floor drains are optional in single-user rooms. Skipping one saves the drain, the trap primer, and the slab work.
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In-wall coordination
Install solid blocking for the grab bars (250 lbf rated) before closing the wall.
Keep the vent, flush valve, and supply stops out of the grab bar mounting zones and the 12" clear space above the bars.
