How do I stop a toilet rocking on the floor?

A toilet pan has a flat foot resting on a floor that is almost never flat, particularly on tiles laid over an old floor. The fixing bolts hold it in place; they are not meant to pull it down onto high spots.

Safety

What you'll need

• Plastic packing shims
• A screwdriver and the correct fixings
• Silicone sealant
• A torch

Step by step

1. Work out which way it moves.Rock it gently and watch the base. Front to back, side to side, or twisting all point to different high spots. Mark where the gap opens.
2. Check the fixings before anything else.Take the caps off and look. Bolts that have worked loose in their plugs, or fixings into a floor that has since been tiled over, are common and easily corrected.
3. Loosen the bolts rather than tightening them.If the pan is not fully supported, tightening pulls it against a high spot and cracks the ceramic, often days later. Back them off before packing.
4. Pack the gaps with plastic shims.Slide thin plastic packers into the gaps until the pan sits solidly without being forced. Plastic, not timber — timber absorbs water and rots.
5. Consider bedding it on silicone instead.A generous bead of silicone under the foot, with the pan pressed down onto it, spreads the load evenly and is the tidiest answer for a slightly uneven floor.
6. Tighten the fixings gently and evenly.Nip them up alternately, firm but not hard. The pan should already be solid before the bolts do anything.
7. Check the pan connector afterwards.A pan that has been rocking has flexed the connector. Look and feel behind for damp, and replace the connector if it looks tired.
8. Trim the shims and seal the base.Cut the packers flush and run a bead of sanitary silicone round the base, leaving a short gap at the back so any leak shows rather than being hidden.
9. Retest with weight on it.Sit on it and shift your weight. Any movement at all means the packing is incomplete.

Tips

• Leave a small unsealed gap at the back of the base. If the pan connector ever leaks, you want to see it on the floor rather than under the pan.
• Plastic shims are sold in mixed thicknesses for exactly this. They cost very little and do not rot.
• If the toilet has been rocking for a long time, budget for a new pan connector as well.

Common mistakes

• Tightening the bolts to stop the rocking — The bolts pull the ceramic down onto a high spot with all the load at one point. Ceramic has almost no tolerance for that and cracks, sometimes weeks later.
• Packing with timber offcuts — Any timber under a toilet will get wet at some point, swell, then rot, and the rocking returns worse than before.

If it doesn't work

Questions people ask