Tank a shower area before tiling

Waterproof shower walls and floor properly before tiling, so leaks can't get into the structure behind.

TSA-01Clear the area and find your stopcockStrip out old fittings, tiles and sealant so you're working on a bare wall and floor. Find your stopcock - usually under the kitchen sink - and check it turns freely, so you can shut the water off fast if you hit a pipe later. Lay dust sheets and keep a bucket and torch to hand.

1 each · Dust sheet

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TSA-02Work out what's behind the wallBefore you fix, drill or cut anything, find out what you're dealing with. Use a stud detector or a magnet to trace the line of screw heads holding the board on - regular screws every 300-600mm mean a stud wall. Tap the wall: a dead thud means masonry or dot-and-dab, a hollow drum sound means a stud wall or a void behind dot-and-dab boards. A small 3mm pilot hole in an unseen spot tells you the rest - pale wood dust is a timber stud, fine grey swarf is a metal stud, and brick or block dust is masonry.

1 each · Stud detector

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TSA-03Check for cables and pipes before you drill or cutCables and pipes can run almost anywhere, not just in the usual safe zones, so always sweep the area with a cable and pipe detector first. Still expect something to be there and prove it isn't - detectors miss cables that are deep, in metal conduit, behind metal-backed board, or outside safe zones, and a metal stud frame confuses cheap detectors even more. If you have any doubt, isolate the circuit at the consumer unit before drilling, and make sure your stopcock is off before cutting into anything that could hide a pipe.

1 each · Cable and pipe detector

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TSA-04Fix loose boards and sort out unsuitable backgroundsScrew down any loose plasterboard before tanking over it - a wet area needs a solid, secure surface. Into a timber stud, use a 40mm wood screw driven into the centre of the stud. Into a metal stud, use a self-drilling metal-stud screw - an ordinary wood screw or a plastic wall plug will strip straight through 0.5mm steel. On dot-and-dab plasterboard, use a fixing long enough to reach through the board and dabs into the solid masonry behind, typically 60-75mm. Lath and plaster is not a suitable background for a wet area - strip it back to masonry or overboard it with plasterboard or a tile backer board before carrying on.

1 box · Wood screws 40mm (box of 200)

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1 box · Self-drilling metal-stud screws (box of 100)

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1 pack · Frame fixings 75mm (pack of 10)

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1 sheet · Tile backer board 1200x900x10mm

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TSA-05Cut and fit around pipework and the shower wasteMark and cut neat holes for the mixer tails, waste pipe and any other pipework using a padsaw or multitool. Aim for a snug fit with a small gap - tanking needs something to bed into around the pipe, not a perfectly tight cut. Recheck TSA-03 for that exact spot before you cut if it's anywhere near a stud wall.

1 each · Padsaw or multitool

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TSA-06Seal internal corners and board joints with tanking tapeCut lengths of tanking tape for every internal corner, the wall-to-floor junction, and every board joint. Bed the tape into a layer of tanking compound with a flat trowel or your fingers, pushing out any air bubbles. Overlap the tape by at least 50mm at corners so there's no gap.

1 roll · Tanking tape (10m roll)

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1 tub · Tanking compound (5kg tub)

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TSA-07Fit a waterproof collar around the shower wasteFit the manufacturer's waterproof collar over the shower waste before tanking the floor. Bed it into tanking compound the same way as the tape, checking it lies flat with no wrinkles. This is usually the first place a shower leaks if it's missed.

1 each · Waterproof shower waste collar

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TSA-08Apply the first coat of tanking membraneMix the product if it's a powder, or use it straight from the tub if it's ready-mixed. Roller or brush on an even coat across the whole shower area - walls up to at least 1800mm high, and right across the floor. Let it dry fully before the next coat; check the tin for the exact time, usually a few hours.

1 tub · Liquid tanking membrane (5kg tub)

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TSA-09Apply the second coat and check coverageApply a second full coat once the first is dry, brushing at right angles to the first coat so you don't miss thin patches. Pay extra attention to corners, joints and the waste collar - these are the weak points. Hold a light close to the surface to check for pinholes or thin spots.

TSA-10Let it cure fully before tilingLeave the tanking to cure for the time stated on the product, usually 24 hours minimum and longer in a cold bathroom. Don't run water or start tiling before that time is up, even if it looks dry. Keep the room ventilated but avoid direct heat, which can crack the membrane as it cures.

TSA-11Tidy up and check before you tileClean tools with water while the membrane is still wet on them - once cured it needs solvent or scraping off. Do a final check for missed patches, especially at corners and around the waste. Take a few photos of the finished tanking for your records, since it's hidden once the tiles go on.

1 pack · Cleaning cloths

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