Siliconing a shower: how to seal, waterproof and protect your shower walls and floor

Person siliconing edge of bath/shower with caulk gun and using blue masking tape as a guideline
(Image credit: Getty Images)

There is an art to siliconing a shower, and once you have mastered it you will be left with a smooth, straight finish with crisp clean lines that give your shower a strong seal that is waterproof and will last for at least three or four years.

When fitting a shower it is essential that all the edges around the area are sealed properly to make sure that they are watertight and waterproof. If you don't get the prep or application right the silicone won’t adhere properly to the surface and let in water which can lead to all sorts of problems.

Here we give you the lowdown on what you need to get a great finish.  

Siliconing a shower: Four steps to a watertight, professional-looking finish 

1. Clean and mask area
Before you add any silicone you need to make sure that area is clean and dry. Start with a stiff hand brush to get rid of any debris and dust, and then use a vacuum to clean the area to be sealed. Wipe down a damp cloth, followed by a wipe down with a dry cloth and leave to dry for 5-10 minutes.

To make sure that your shower room ideas look as good as you imagined you need to use masking tape to get crisp even edges on your silicone. Blue painter's tape is a good choice. Place a length of the tape either side of where the silicone is to go. Leave a gap of around 3mm on both sides.

2. Prepare your silicone gun
Get a sharp knife to cut the silicone nozzle at 45 degrees around 5-20mm down the nozzle, depending on what size bead you'd like. (It's best to start small and then go larger if required.) Place the cartridge in a caulking gun and squeeze the trigger until you get a tight fit.

3. Apply the silicone
Depending on the size of the gap between shower edges and walls and floors you should only need to add one run of silicone. But if you have deep edges, fill these with a small bead of silicone and run a wet finger along to make sure the silicone is pushed in.

To finish, place the gun at a shallow angle – starting in one corner – and squeeze the trigger. As soon as the silicone appears, start moving along the edge. Use a consistent speed and pressure to get an even bead of silicone. 

4. Finish up and smooth out
Now smooth the silicone with a wet finger, damp sponge or use a silicone finishing tool. If using a finger simply wet and drag along the silicone. Have a cloth ready to wipe off the excess silicone. Do the same with a damp sponge. 

If using a finishing tool, spray the silicone with a fine mist of water, choose your shape on the finishing tool and drag along the silicone to finish.

Apply these same steps and principles for corners on walls and around bathroom fittings. 

Person using a silicone finishing tool in a wall corner

To get a smooth even finish on silicone use a finishing tool (Image credit: Getty Images)

How long after adding silicone can I use the shower?

Newly applied sanitary silicone will typically start to dry within 15 minutes, but you will need to leave it for at least five or six hours before having any continual contact with water. 

However, ideally to make sure that it has fully cured and will repel water and moisture you won’t be able to use your best shower head for around 24 hours. If possible leave for 48 hours.  

Can I put new silicone over old? 

You can but it’s not recommended. It’s pointless adding a new layer of silicone to old silicone, especially if the old silicone is in poor condition. It won’t adhere to the old silicone meaning it won’t create a waterproof barrier and it won’t look pretty.

If you are going to add new silicone sealant it is best to remove the old silicone. Use a Stanley knife to cut and remove or invest in a silicone removal kit with sealant finishing tools for the new silicone. 

Should I use silicone or caulk for a shower? 

For areas that are frequently in contact with water and moisture you need to be using a silicone sealant. Caulk and silicone have very similar qualities, both are waterproof, but silicone is more flexible which makes it ideal for areas like a shower tray or a bath.

However, if you are painting skirting boards in your bathroom or shower room you can think about how to use decorators caulk to seal and fill gaps. It is moisture resistant and can be painted over unlike silicone.  

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.