Should bathroom and kitchen ceilings/walls use moisture-resistant (green) gypsum board — and is it waterproof?

Short answer: YES, use moisture-resistant (MR) board in bathrooms, kitchens and other damp/humid rooms instead of standard board — but understand its limit: MR board is moisture-RESISTANT, NOT waterproof, so it handles humidity and the odd splash, but it is NOT a waterproofing layer and on its own it must NOT be relied on in a directly-wet zone like inside a shower. The difference: standard gypsum board (usually ivory/grey faced) soaks up moisture and degrades — it sags, softens and grows mould in a humid or splashed environment; MR board (conventionally GREEN-faced so trades can tell them apart) has water-repellent additives in the core so it resists humidity and occasional moisture far better and stays stable. WHERE to use it: bathroom and kitchen ceilings and walls, utility/laundry rooms, and generally around wet areas and splash zones — that's exactly what it's for. BUT for a DIRECTLY-WET area — inside a shower/wet room, behind tiles that get soaked — MR board alone is NOT enough: those areas need a proper WATERPROOFING/TANKING system applied over the board (a liquid membrane or tanking kit) or a dedicated cement/fibre tile-backer board, THEN tiling. So the rule: MR (green) board as standard for the room (humidity + splash), plus a proper tanking system in the actual wet zone. Spec MR board for damp rooms, and never treat it as the waterproofing.

Standard vs MR (green) board: - Standard board: soaks up moisture -> sags, softens, moulds in humid/splashed areas. - MR (green) board: water-repellent additives in the core -> resists humidity + occasional moisture, stays stable. Green facing = the trade tell-apart.

Where to use MR board: - Bathroom + kitchen ceilings/walls, utility rooms, splash zones — its whole purpose.

The waterproof limit (important): - MR board is resistant, NOT waterproof. In a shower/wet zone or behind soaked tiles it needs a waterproofing/tanking system over it (liquid membrane/tanking kit) OR a cement/fibre backer board, then tiles. See bathroom waterproofing. - MR board defines the board type — see gypsum board grades.

Common mistake: using standard board in a bathroom (it fails), OR assuming MR/green board is waterproof and tiling a shower straight onto it with no tanking (it leaks/fails). MR board for the damp room + proper tanking in the wet zone. Let a gypsum and finishing specialist spec the board and the waterproofing. Anyone had standard board fail in a bathroom?