Fix a toilet that rocks on the floor

Find why your toilet rocks, refix it securely to the floor, then reseal the base for a solid, leak-free fit.

TR-01Turn off the water and empty the cisternFind the isolation valve on the pipe behind or under the cistern (a small slotted or lever valve) and turn it off. If there isn't one, turn off the water at the mains stopcock, usually under the kitchen sink, and check it turns before you start. Flush the toilet to empty the cistern, then soak up any water left in the pan and cistern with an old towel or sponge.

TR-02Work out what's actually movingSit on the toilet and gently rock it to find exactly where the movement is coming from — the pan base, the cistern, or the floor flexing underneath. Check the base for cracks in the ceramic; a cracked pan needs replacing, not re-fixing. Check whether the existing screws are missing, snapped or just loose, and whether old sealant around the base has already cracked, which suggests it's been moving for a while.

TR-03Remove the old sealant and fixingsCut through the old bead of sealant around the base of the pan with a sharp blade or sealant scraper, then peel it away. Pop off the plastic caps over the fixing points and remove the old screws or bolts. Wipe away any leftover sealant residue with methylated spirit so the floor and pan edge are clean and dry.

1 each · Sealant scraper or sharp blade

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1 bottle · Methylated spirit

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TR-04Check your floor typeTap the floor around the pan. Solid floors (concrete or screed, common under tiled or vinyl bathroom flooring) feel hard and give a dull knock. Timber floors (floorboards or chipboard, common in older houses and upstairs bathrooms) sound hollow and may flex slightly underfoot. This decides the fixing: solid floors need a plug and screw into the concrete, timber floors take a screw straight into the board or joist below.

TR-05Reposition the pan and mark the fixing holesSit the pan back in place, lined up with the waste pipe and cistern connections, and check it sits flat with no rocking before fixing anything. If the floor is uneven, slide plastic shims under the base until it's solid, ready to trim once fixed. Mark through the fixing holes in the base onto the floor with a pencil.

4 each · Plastic shims

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TR-06Drill safely — check what's under the floor firstBathroom floors often hide water pipes, waste pipes, and sometimes cables for underfloor heating or an extractor fan. A cheap detector can miss pipes buried deep or run in metal, so use a cable and pipe detector but still treat the floor as if something is there until you've proved otherwise. Know where your stopcock is and check it turns before you start, so you can shut the water off fast if you hit a pipe. If there's any doubt, isolate the electrics at the consumer unit and turn off the water at the stopcock before drilling.

1 each · Cable and pipe detector

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TR-07Fix into a solid (concrete or screed) floorDrill through the marked holes with a 6mm masonry bit to a depth of about 40mm. Push a matching wall plug into each hole, then drive in the fixing screw supplied with the pan (usually brass or stainless, no longer than 40mm) until just snug. Don't overtighten — ceramic cracks easily. Refit the plastic caps once done.

2 each · Masonry wall plugs

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2 each · Brass or stainless fixing screws

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1 each · Masonry drill bit 6mm

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TR-08Fix into a timber floorDrill a 3mm pilot hole through the marked holes into the floorboard or joist below, about 20mm deep. Drive in the stainless steel screws supplied with the pan (typically 40-50mm) by hand or on a low drill setting until just snug — stop as soon as it's firm. If the floor feels soft or spongy, you may be fixing into rotten timber rather than solid board; get this checked before relying on it.

2 each · Stainless steel fixing screws

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1 each · Pilot drill bit 3mm

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TR-09Reconnect the water and check for leaksTurn the isolation valve or stopcock back on slowly and let the cistern fill. Flush a few times and check around the base, the cistern connections and the waste pipe for any drips. Gently tighten any loose pipe connections — fittings should be snug, not forced.

TR-10Reseal the base and tidy upOnce you're sure there are no leaks and the pan is solid, run a neat bead of sanitary sealant around the base where it meets the floor, leaving a small gap at the back so any future leak can show. Smooth the bead with a wet finger and leave it undisturbed for the time stated on the tube before use. Wipe down the floor and dispose of the old sealant and packaging.

1 tube · Sanitary silicone sealant

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