I'm renovating my bath and am interested in a walk-in shower area (i.e. no doors). How can I calculate a "safe" distance from the shower head for the door area? Are there design guidelines for distance (and perhaps direction) that water is expected to splash?
What you are creating here is known as a "Wet room". I could not find any set rules for distances, however the entire concept and building method is different than for conventional bathrooms with enclosed showers. Wet rooms can be built to any size or shape. The most important concept is that the room needs to be "tanked". What this means is that the walls, floors, windows etc must be completely sealed and waterproof. Drainage is extremely important, so floor slope design is also different than conventional rooms. Before you consider an open shower, visit some sites that describe the unique needs and features of a wet room. A Google search for "Wet Rooms" will give you dozens of sources. Good Luck
You can also look at Wet Zones. These come in a variety of styles but the one we used from Aqua Dry consists of a raised base you fix above the existing floor level.
This base has the correct drainage slopes built in - all you have to do is make sure the floor on which it stands is level. The range includes side and end panels which fit onto this raised area.
The arrangement we have is (approximately):
The shower head (not included in the kit) is virtually directly over the drain and points more or less straight down. We don't get any water outside the shower area beyond a few splashes.
The walls still need to be made waterproof as does the junction between the walls and the base - but the kit comes with all the tape, glue and waterproofing needed. All you need to do is add the shower itself and the tiles.