How to caulk skirting boards

Video by B&Q. This walk-through is based on the video “How to caulk” from the B&Q YouTube channel, which covers the basics of applying caulk to skirting boards and getting a tidy finish. Short and to the point — worth a watch before you load the gun.

1. Choose the right caulk for the job

Decorator’s caulk — sometimes called acrylic caulk or flexible filler — is what you want here. It stays slightly flexible after it dries, which matters because houses move a little with the seasons and a rigid filler will crack at the joint. More importantly, decorator’s caulk is paintable. Silicone is not, so keep that for wet areas like bathrooms and kitchens.

Pick up a standard white decorator’s caulk from any builders’ merchant or DIY shop. Everbuild, UniBond, and Geocel all make decent versions. You will also need a basic caulking gun — the cheap squeeze-trigger type is absolutely fine for this job — and a small bowl of water.

2. Prepare the surface properly

If you are refreshing an existing room rather than starting from scratch, the old caulk will probably need to come off first. Score along it with a craft knife, then peel it away. It usually comes off in a strip once you get an edge started. Any stubborn bits can be scraped back with a filling knife — just be careful not to dig into the plaster or dent the skirting.

Once the old material is off, wipe the area down with a damp cloth to remove dust and any loose paint flakes. Let it dry fully before you do anything else. Applying fresh caulk to a damp surface is a reliable way to make it peel within six months. That said, if it’s a newly plastered wall, make sure you’ve applied a mist coat first — bare plaster is too absorbent and will pull moisture straight out of the caulk before it has a chance to skin over properly.

3. Cut the nozzle at the right angle

Cut the plastic nozzle of the caulk tube at roughly 45 degrees, using a craft knife or a decent pair of scissors. The size of the hole determines the size of the bead, so cut near the tip to start with — you can always open it up a little if the gap is wider than expected. A hole about 3–4 mm across is right for most skirting board gaps.

Fit the tube into the gun and give the trigger a couple of test squeezes onto a scrap of cardboard first. You want the caulk flowing freely before you put gun to wall, not spurting out in lumps because you were squeezing too hard to get it started.

4. Apply the bead steadily along the gap

Hold the gun at roughly 45 degrees to the wall, nozzle pointing into the gap. Press the trigger gently and move along the length of the skirting in one smooth pass. Aim for a consistent speed — too slow and you get a fat, messy bead; too fast and the caulk strings out and leaves gaps. A steady pace somewhere in between is what you are after.

Work in manageable lengths — maybe a metre at a time — rather than trying to run the whole wall in one go. The caulk starts to skin over within a few minutes, so shorter runs give you time to smooth each section before it firms up. Mind you, in a cold room it will stay workable a little longer, which can be handy.

5. Smooth the bead with a wet finger

Wet the tip of your index finger in the bowl of water — just damp, not dripping — and run it along the caulk in one continuous stroke. The water stops the caulk from sticking to your skin and lets you push it firmly into the gap while smoothing the surface flat. Do this in one pass if you can; going back over it repeatedly just moves mess around.

Wipe your finger on a damp cloth after each pass rather than letting the excess caulk build up on your hand. Some decorators prefer a purpose-made caulking tool or the back of a teaspoon dipped in water — both work fine. To be fair, a wet finger is quicker and gives you more feel for how much pressure to use.

6. Leave it to dry before painting

Most decorator’s caulk is touch-dry within an hour in normal room conditions. However, do not paint over it until it has cured properly — ideally 24 hours, and longer if the room is cold or the gap was wide enough to take a thicker bead. Painting too soon is the most common reason caulk cracks: the paint skin forms before the caulk beneath has fully dried, and as it shrinks you end up with hairline splits along the line.

Once dry, check the bead. If it has sunk slightly in any spots, fill those sections again and smooth them back in. Then paint — the caulk will take emulsion and gloss equally well. A small brush to cut in around the bead gives the cleanest finish, particularly where the skirting colour meets the wall colour.

When to call a handyman

Caulking skirting boards is usually a straightforward DIY job, but call Richard if the gaps are large and uneven — over about 5 mm — because they need filling with coving adhesive or frame sealant first, or the caulk will just sink and crack. It’s also worth getting help if you are caulking a whole house after replastering and want the decorating prep done right first time. Richard covers handyman repairs across Sandwich and the surrounding East Kent villages.