Introduction

When you need to seal the joins between a wall and a basin, shower tray, bath, or sink unit, you can't use grout or an ordinary filler. This is because these fittings move and flex and a rigid seal would crack even under the slightest pressure.

Cracks in the grout or seal would then allow water to seep in and create stains, and any hidden build-up of moisture could cause damp and mould growth to occur. Instead, it's best to use a silicone rubber caulking compound, which, even when dry, remains a little flexible. These compounds come ready-mixed in tubes or in cartridges (applied using a 'gun' mechanism or a finger trigger) and in a range of colours to match your tiles. The compounds will easily fill a gap of up to 3mm (1/8in) wide, but if your gap is wider, then it will need packing out: use lengths of soft rope or even twists of soaked newspaper.

Cut off the nozzle end of the tube or cartridge at 45 degrees - this makes it easier to apply, and remember the amount of nozzle you cut off will determine the size of the 'worm' of sealant that is extruded. If you don't achieve a perfectly smooth line when you squeeze out the sealant into the crack, don't worry: smooth out any ripples or irregularities with the back of a wet teaspoon.

Don't try smoothing with your finger - it always ends up worse than when you started. Caulking compound isn't the only way to seal gaps: you can also use ceramic coving. These are rounded quadrant tiles and there are also bull-nose tiles - with a nicely rounded finished end - used for the final end of a straight run. You can also seal joins with plastic coving, which you cut to length and glue on using a proprietary adhesive.

Step by Step Instructions

1 Mask off

In order to guide your hand and eye - and keep the 'worm' of sealant in a straight line - mask off above and below the area where the sealant is to be laid. Use a low-tack tape and run it in continuous strips where possible at each side of the fitting.

2 Apply the sealant

Cut the nozzle at 45 degrees - don't cut too much off the end of the nozzle or you'll get too thick a 'worm'. Using even pressure, squeeze the sealant from the tube (or use the cartridge gun or finger trigger). Work carefully along the join applying the sealant.

3 Remove masking tape

Smooth out any irregularities in the sealant with the back of a wet teaspoon, and remove the masking tape. Don't rip the tape off: remove it slowly and evenly so you don't pull the sealant away as well. Allow the sealant to dry thoroughly, according to the maker's instructions.

Removing Old Sealant

If old sealant round a bath or sink has become stained or discoloured, brush on a proprietary sealant remover, leave for 15 minutes, then scrape the old sealant off. Thoroughly clean the area then apply new sealant.