A bathroom is not one environment, it is four. Inside the shower is continuous wetting. The wall behind the basin and the area beside the tub get splashed and wiped. The ceiling above the shower takes condensation without ever being splashed. And the wall behind the door is, in moisture terms, an ordinary bedroom wall. Specifying one board and one paint for all four is why bathrooms develop problems in specific, predictable places.
Board selection by zone. Inside a shower or tub surround, a cement or fibre-cement tile backer belongs behind the tile — moisture-resistant drywall is a different product for a different job and is not intended for continuous wetting. In the splash zone around the basin and outside the tub, a moisture-resistant board is appropriate. Elsewhere in the room standard board is fine, and using tile backer everywhere is money spent where it does nothing. The ceiling is where the specification is most often wrong: it is the coldest surface in a humid room and therefore the first place condensation forms, so a moisture-resistant or mould-resistant board there is worth the small premium even though nothing ever splashes it.
Taping and finishing to a level that survives the light. Bathrooms are small, brightly lit, and increasingly lit from the side by mirror sconces, which is the most unforgiving light there is for drywall. Raking light across a wall shows every ridge in a taped joint and every ring around a screw. That means joints feathered wide, corners run true, and a skim where the light will hit hardest. The other bathroom-specific detail is at the tile edge: where tile stops partway up a wall, the drywall face has to sit correctly relative to the tile plane so the transition can be trimmed or bullnosed cleanly, and that means the boarding thickness was thought about before the tile was chosen.
Paint that lasts in a wet room. Bathroom paint fails in two ways: it peels where it was applied over a surface that was not sealed and where condensation sits, and it grows mould in cold corners. A quality acrylic in an eggshell or satin sheen resists moisture and takes cleaning, while a flat finish on a bathroom wall is difficult to wipe and holds dirt. New drywall needs a proper primer sealer, not a diluted coat of finish paint, because the paper and the compound absorb at different rates and the difference shows through as flashing. Ceilings get the same treatment as walls in a bathroom rather than a chalky ceiling flat, because a ceiling flat has nothing in it to resist condensation.
Wallpaper is possible, with conditions. A well-ventilated powder room with no shower is a good candidate and a great place for a paper with real presence, since the surface area is small and the visual payoff is high. A main bathroom with a shower is harder: the substrate must be sealed and sized properly, a vinyl or non-woven product handles humidity far better than a traditional paper, and the seams need to be kept away from the wettest areas. Without adequate extraction, no wallpaper survives long, which brings the conversation back to the fan.
Ceilings. A well-finished, well-painted flat ceiling is the simplest option and usually the right one. Where a bulkhead conceals ductwork or a relocated waste line, it is worth designing rather than tolerating — aligning it with the shower enclosure or the vanity run makes it read as intentional. Tongue-and-groove ceilings suit older island homes well, and need a finish on all faces including the backs of the boards, plus room for movement, because a bathroom ceiling cycles through humidity twice a day.
Trim and moulding. Baseboard in a bathroom lives at the wettest point in the room. MDF baseboard wicks water from the floor and swells from the bottom edge — a common and entirely avoidable failure — so PVC, primed solid timber or a moisture-tolerant alternative earns its place here, sealed on the bottom edge before fixing and caulked to the floor so water cannot get behind it. Casings and panelling follow the same logic, and sill details at a bathroom window need particular attention because condensation collects there.
Mirrors and hardware are the details people touch. A mirror needs blocking positioned during framing; a large frameless mirror is heavy and cannot rely on adhesive alone. Towel bars, hooks, a roll holder and grab rails all need solid backing rather than drywall anchors, and their positions are worth deciding on the plan — a towel bar within reach of the shower, a hook where a dressing gown actually goes, a rail that does not foul the door swing. It is the least expensive part of the job and the part interacted with most often.