Exerpts from 41 Guidelines for Bathroom Planning

Vanity height should fit the user(s).
The bottom edge of the mirror over the lavatory should be a maximum of 40" above the floor or a maximum of 48" above the floor if it is tilted.
The minimum clearance from the centerline of the lavatory to any side wall is 15".
The minimum clearance between two bowls in the lavatory center is 30", centerline to centerline.

In an enclosed shower, the minimum usable interior dimensions are 34" x 34". These dimensions are measured from wall to wall. Grab bars, controls, movable and folding seats do not diminish the measurement. Physical constraints of a job site may require this to be reduced to 32" x 32".
Showers should include a bench or seat that is 17"-19" above the floor and a minimum of 15" deep. Built-in permanent seats should not encroach upon the minimum interior clear floor space.
The shower doors must open outward, into the bathroom.
Steps should not be planned at the tub or shower area. Safety rails should be installed to facilitate transfer to and from the fixture.
All showerheads should be equipped with pressure balance/temperature regulator or temperature limiting device.
Shower Controls should be accessible from inside and outside the fixture. Shower controls should be located between 38"-48" above the floor (placed above the grab bar) and offset toward the room.
Tub controls should be accessible from inside and outside the fixture. Controls should be located between the rim of the tub and 33" above the floor, placed below the grab bar and offset toward the room.

A minimum 16" clearance should be allowed from the centerline of the toilet or bidet to any obstruction, fixture or equipment (except grab bars) on either side. Physical constraints of a job site may require this to be reduced to 15". When the toilet and bidet are planned adjacent to one another, the 16" minimum centerline clearance to all obstructions should be maintained. Physical constraints of a job site may require this centerline clearance to be reduced to 15".
Toilet paper holder should be installed within reach of a person seated on the toilet. Ideal location is slightly in front of the edge of the toilet bowl, centered at 26" above the floor.
Compartmental toilet areas should be a minimum 36" x 66" with a swing-out door or a pocket door.

The clear space at doorways should be at least 32" wide and not more than 24" deep in the direction of travel.
Walls should be prepared (reinforced) to receive grab bars at the time of construction. Grab bars should also be installed in the bathtub, shower and toilet areas at the time of construction.
In the tub/shower area, storage for soap, and other personal hygiene items should be provided within the 15"-48" above the floor within the universal reach range.
All flooring should be slip resistant.

Mechanical ventilation systems to the outside should be included in the plan to vent the entire room. The minimum size of the system can be calculated as follows:
Cubic space (LxWxH) x 8 (changes of air per hour)
60 minutes = Minimum cubic feet per minute (CFM)
Ground fault circuit interrupters must be specified on all receptacles, lights and switches in the bathroom. All light fixtures above the bathtub/shower units must be moisture-proof special-purpose fixtures.
Every functional area in the bathroom should be well illuminated by appropriate task lighting, night-lights, and/or general lighting. No lighting fixture, including hanging fixtures, should be within reach of a person seated or standing in the tub/shower area.
When possible, bathroom lighting should include a window/skylight equal to a minimum of 10% of the square footage of the bathroom.
Use clipped or radius corners for open countertops; countertop edges should be eased to eliminate sharp edges.
Any glass used as a tub/shower enclosure, partition, or other glass application within 18" of the floor should be one of three kinds of safety glazing: laminated glass with a plastic interlayer, tempered glass or approved plastics such as those found in the model safety glazing code.