Fitting moisture-resistant plasterboard in a bathroom yourself

Which plasterboard and frame suit a bathroom

Moisture-resistant plasterboard, usually green-faced, is the right choice for any wall or ceiling in a bathroom that will be tiled or painted, including areas away from direct water contact. It costs more than standard board but the difference is small next to the cost of redoing a bathroom wall, and it is not a place to economise. Twelve and a half millimetre board is standard for walls; use two layers, or a thicker board, where the wall will carry a heavy mirror cabinet or grab rail.

For the frame, galvanised steel stud profiles are the sounder choice over timber battens in a bathroom, since steel does not swell, shrink or rot if it ever gets damp behind the board. In an older Tallinn flat with an uneven masonry or panel wall, a steel frame also gives you a straight, level surface to work from without chasing the wall itself. Timber battens are acceptable if they are kiln-dried and you seal the frame cavity properly, but steel is less to think about later.

Frame spacing and fixing, the basics

Vertical studs go at 400 mm centres for bathroom board, not the 600 mm sometimes used elsewhere in a flat — tiled board carries more weight and needs closer support to stay flat over years of temperature and humidity changes. Run a horizontal noggin at the height of any wall-hung basin, WC cistern or towel rail bracket, fixed back into the wall or floor structurally, not just screwed into the plasterboard.

Check every stud with a spirit level before boarding, not after — a millimetre of lean over a 2.4 m wall becomes an obvious ripple once tiled. Leave a gap of roughly 10 mm at floor level, and at least the same where the frame meets a shower tray or bath, so the board does not sit in standing water or wick moisture up from the floor.

A screw pattern that keeps the board flat

Use coarse-thread drywall screws long enough to bite at least 10 mm into the steel or timber behind — typically 25 mm for single-layer 12.5 mm board. Space screws at 200–250 mm along each stud, and keep them at least 10 mm from the cut edge of the board and 15 mm from a factory edge, closer than that and the board tends to crumble around the screw head.

Drive each screw so the head sits just below the paper face without tearing it — a proper drywall screwdriver with a depth-setting clutch makes this far easier to get consistent than a standard drill. A screw sitting proud will telegraph through tile adhesive as a visible bump; one driven too deep loses its grip on the board entirely.

• 400 mm stud centres for bathroom board, not 600 mm
• 25 mm coarse-thread screws for 12.5 mm single-layer board
• 200–250 mm screw spacing along each stud
• 10 mm minimum edge distance from a cut edge
• Screw heads set flush, not torn through the paper or left proud

Jointing and corners before waterproofing

Every joint between boards needs jointing compound and paper or fibreglass tape, applied and sanded flat before anything else happens to the wall. Fill screw dimples at the same time, in two thin coats rather than one thick one, since a thick fill tends to crack as it dries. Internal corners take paper tape folded into the angle; external corners take a metal or plastic corner bead screwed or bedded into compound.

This is the stage most amateur jobs go wrong: rushing the joints, sanding through the paper face, or skipping tape on the theory that tiles and adhesive will cover the gap. Tile adhesive is not a filler — a joint that is not properly flat and taped will show as a hairline crack in the grout within a year or two, and by then it means coming back through the tiles to fix it.

Waterproofing before tiling

Once joints are sanded flat, the whole tiled area needs a liquid waterproofing membrane, painted on in at least two coats, extending up the wall well above shower head height and across the full floor if it is a wet room. Pay particular attention to the internal corners and the junction between wall and floor — these are reinforced with a waterproofing tape or fleece strip bedded into the first coat, not just painted over.

This layer is what actually keeps water out of the wall structure; the tile and grout above it are largely decorative in that respect. Skipping or skimping on it is the single change most likely to turn a small bathroom refresh into a damp problem behind the tiles a few years later.

When to stop and call someone in

Boarding a straightforward bathroom wall on a steel frame is a realistic weekend job for someone with basic tools and patience. Where it usually makes sense to bring in a professional is a ceiling with a ventilation fan or downlights to work around, a wall that will carry real weight such as a wall-hung WC frame, or any point where the frame needs fixing into a wall you are not certain is load-bearing — that last one is not something to guess at, and we do not touch load-bearing walls ourselves either.

If the boarding work is small — one wall, a ceiling patch, a repair after a leak — plasterboard work from us starts at 28 € per job and covers exactly this kind of task without a full renovation on top. Where the bathroom is being redone in full, from frame through tiling and fittings, that is priced as a fixed-quote bathroom renovation from 3 500 € per job, valid for 30 days once we have seen the space or photographs.