How to caulk a gap

Gap fillers and silicone sealants are designed for different applications. For interior gaps around skirting boards, architraves, cornices and trims, use a paintable caulkgap filler rather than a silicone sealant. Gap fillers can typically be painted once cured, helping create a seamless finish.

Remove any loose paint, old filler, dust or debris from the gap. A clean surface helps the filler adhere properly and creates a neater result. If the surrounding surfaces are dusty, wipe them down and allow them to dry before starting. For highly visible areas or where extra precision is required, apply masking tape along both sides of the gap. This can help create cleaner edges and reduce the amount of cleanup required later.

Select a wet area silicone sealant suitable for bathrooms, laundries or kitchens. These products are designed to provide a waterproof seal and often contain mould-resistant properties to help keep the finished joint looking cleaner for longer. Sealants are available in a range of colours, so choose one that complements the surrounding tiles, grout or fixtures.

Load the sealant cartridge into the caulking gun and cut the nozzle at a 45-degree angle. Start with a smaller opening, as more sealant can always be applied if needed. A smaller nozzle opening often provides better control and helps avoid applying too much product, making it one of the most useful caulking tips for achieving a neat finish.

Hold the nozzle at a consistent angle and apply a continuous bead of filler along the gap using steady pressure on the trigger. Aim to fill the gap completely without applying excessive product. For longer gaps, work in manageable sections to maintain control and consistency.

Before the filler begins to skin over, use a caulking tool or smoothing tool to shape the bead. Many smoothing tool kits include a range of profiles and sizes, making it easy to match the width of the gap and achieve a consistent finish. Work along the bead using steady pressure and wipe excess product from the tool regularly. If a section looks uneven, simply smooth it again while the filler is still workable.

If too much filler has been applied or the finish isn't quite right, use the removal edge of the smoothing tool to remove excess product and reshape the bead. This is often easier and cleaner than wiping away excess filler by hand. If gaps or low spots become visible after smoothing, apply a little more filler and smooth the area again before it begins to dry.

If masking tape was used, remove it while the filler is still wet to help create a clean edge. Pull the masking tape away slowly at an angle for the best result.

Allow the filler to dry according to the manufacturer's instructions before painting. Drying times can vary depending on the product used, the size of the gap and the conditions in the room. Once the filler has cured completely, it can usually be painted to match the surrounding surface. Painting over the filler helps blend the repair into the wall, trim or skirting board for a professional-looking result.