Caulking: 11 must-know tips for a smooth and professional finish

Caulking gun placing white sealant on black background
Caulking like a professional needs a consistent pressure when applying (Image credit: Getty Images)

Caulking in the kitchen, bathroom or anywhere in the home can be a scary thought, especially for those who are new to the art. 

But it's not as difficult as you might think and once you have learnt how to caulk, you will be getting smart, smooth caulk beads that are watertight and look good. 

Caulk is a sealant similar to silicone. Both are typically applied with a caulking gun, in the same way. They have slightly different properties but the process of adding and finishing are almost identical.

Here we give you the lowdown on all the tips and techniques you need to know to make your caulk and sealant look like it has been done by a pro. 

1. Remove old caulking before replacing with new

You can’t place new caulk on top of old caulk, especially if it is in poor condition. So to get the best finish you need to remove the old caulk. For example, if you are caulking skirting boards you can use a Stanley knife – cut as close to the edges as possible and pull out.

But a safer option is to invest in a specialist caulk removal tool. These can run under the caulk and pull up for a clean removal. These are often found in a caulk/sealant finishing kit. 

Person running a caulking gun across the top of skirting board

You will need to remove old caulk before putting new caulk in (Image credit: Getty Images)

2. Clean your surface before caulking

Before you even think about adding any caulk or sealant to a surface you need to make sure that it is clean. If there is dust, dirt, debris or old caulk in the area to be used, the caulk will not adhere as well as a clean, debris free surface.

Sweep and vacuum to get rid of dust, dirt and debris. But if the surface is greasy or has soap scum on it – typically a kitchen or bathroom – this will need cleaning off. You can use surgical spirit and a clean cloth for a quick clean. 

Alternatively, dip a cloth or scourer in a solution of sugar soap. What is sugar soap you ask? A mild but powerful detergent. Once cleaned, rinse with warm, clean water and dry the area with a dry cloth or old towel.   

3. Consider investing in a decent caulk gun

If you are an occasional caulker, you don’t need to spend too much on a caulking gun. Typically cheaper caulking guns have skinny cradles and less robust handles, but are still good for occasional jobs.

If you are a regular caulker, look for a gun with a half cradle that offers more support and large handles for more control over the caulking process. 

Orange caulk gun on yellow background

If you have a lot of caulking, a caulking gun that offers more support with a larger handle is best (Image credit: Getty Images)

4. Choose the right caulk or silicone for the job

For most indoors jobs, it is a toss up between decorators caulk and silicone sealant. Both have very similar properties, but decorators' caulks will be used for sealing small gaps around doors, windows and skirting. It acts like a flexible filler and can be painted.

A sealant will be used for jobs like siliconing a shower as it is waterproof and stays more flexible. An important factor for areas that need movement but also need to stay watertight like a bath. For exterior jobs, use a specialist exterior caulk or sealant.  

Two tubes of caulk and silicone on wooden background

Whether you choose caulk or silicone is dependent on the job (Image credit: Future/Steven Jenkins)

5. Snip the tip at an angle and start small

Typically you cut the tip at an angle as this makes it easier to apply to whatever surface you are working with. How far down the nozzle you cut determines the size of the bead. The further down, the larger the flow of caulk or sealant will be. 

As a general rule start small, around 6-8 mm for a small bead. Test and snip again if needed. Use a Stanley knife to cut the tip of the nozzle, cutting away from your body and hands.  

6. Get crisp, clean edges with tape

To create a straight, crisp clean edge to your caulk lines use blue painters tape. Place a length of the masking tape on either side of the area where the silicone is going to go. Leave a gap of around 3mm on both sides from the centre of the caulk area. This might need to be larger depending on the job.  

Person siliconing edge of bath/shower with blue masking tape as a guideline

Using tape will give you smart, crisp edges (Image credit: Getty Images)

7. Caulk like a pro with even speed and pressure

To get an even run of caulk you need to use a consistent speed and consistent pressure. Start in a corner, squeeze the handle and as soon as the caulk comes out start moving. Not too fast otherwise you will get a thin, stringy bead, and not too slow so you get a lumpy, thick bead.

When applying the caulk try to keep your arms at the same angle and steady. Move your body rather than your arms to get a consistent bead of caulk. Not sure on the process, then practice.

8. Practice, practice, practice 

If you are new or a novice to the art of applying caulk or sealant, it is a good idea to take a few practice runs before jumping straight in. Get a piece of wood or cardboard – something you can throw away – and run a line along it. 

Keep doing this until you get a consistent and even flow and are confident to carry on. This shouldn’t take long, but it’s definitely worth the time. If you are going to tile a kitchen wall or similar make sure to start in an out of way area – just in case it doesn’t go quite to plan. 

9. Finish with a caulking kit 

Once you have added your caulk or sealant it needs to be finished to get the best seal and look. A lot of pros simply suggest using a wet finger to quickly get the job done. Make sure you have a cloth on hand to wipe off the excess.

Another option is to use a damp sponge – more hygienic. But if you want a real smooth finish or a different shape or size then use a caulk finishing kit. This will help ensure that you get a uniform professional looking finish. But don’t forget to finish the caulk within 5-10 minutes as the caulk only stays workable for around 15-20 minutes. 

Orange 4-peice caulk finishing kit on wood background

Caulking kits can give a professional finish (Image credit: Future/Steven Jenkins)

10. Cap your caulk ready for the next job 

When you finish a job there’s a good chance that you will still have some of your best caulk or best bathroom sealant left in the tube. To stop the caulk drying out and causing a blockage push an appropriately sized  nail down the nozzle and wrap masking tape around the nozzle and tip.  

Alternatively, wrap the nozzle in plastic wrap/cling film and then secure with masking tape or painters tape. If you have nothing to hand squeeze out a blob of caulk or sealant let it dry a little, lick fingers and roll into a ball. Place the ball on top of the nozzle.  

If the caulk does dry in the nozzle use a screw to help pull it out. Screw it in and then pull out.

11. New nozzle please 

You can buy caulk tubes without nozzles as well as with nozzles. Replacement nozzles are inexpensive and always handy to have. If you leave a nozzle lying around for a while it may split and need replacing. Many nozzles come with covers to stop them being blocked with dry caulk.  

Steve Jenkins

Steve is Homebuilding & Renovating's DIY content editor, and has been a writer and editor for two decades. He is an avid DIYer with over 20 years of experience in transforming and renovating homes. He specialises in painting and decorating, but has strong all-round building skills, having previously worked in the industry for 10 years.