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How to caulk a window in bathroom?

notsure2026

Hi,

I noticed last night that one of the windows in our bathroom is missing caulk on the left long side.
Just wondering the best product to use to seal this? The gap is around 4mm.
I understand I will need to use rubbing alcohol to clean it up before applying the caulk is this correct also?

Sorry very new to any house maintenance so apologies for the questions and possible incorrect naming

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MitchellMc

Welcome to the Bunnings Workshop community @notsure2026. It's terrific to have you join us, and many thanks for your question about filling a gap.

No need to apologise at all, this is a very common question and you are looking at exactly the right thing.

For a bathroom window like this, the best product to use is a wet-area silicone sealant. Silicone stays flexible and handles moisture much better than standard gap filler, which is important around windows in bathrooms. Only use a paintable gap filler if you are certain you want to paint over it afterwards, as silicone cannot be painted.

You do not need rubbing alcohol specifically. The main thing is that the area is clean, dry and free of dust, soap residue or loose material. A wipe with a damp cloth, followed by letting it dry, is usually enough. Alcohol is sometimes used by professionals, but it is not essential for a small job like this.

With a 4 mm gap, silicone is perfectly suitable. Masking tape along both sides of the gap is a great idea, as it helps keep the bead neat. Apply a steady bead of sealant, then smooth it with a lightly wet finger or a finger dipped in soapy water. Once you are happy with the finish, remove the tape straight away while the silicone is still wet.

Take your time and do not overthink it. This is a straightforward job and a great place to build confidence with basic home maintenance.

Here's a helpful step-by-step guide: How to apply silicone sealant.

Please let me know if you have any questions.

Mitchell

notsure2026

Thank you so much for your prompt assistance! Is there a specific product from your link that you recommend more than another?

MitchellMc

I'd go with Selleys 300g White Wet Area Waterproof Silicone Sealant @notsure2026.

Mitchell

notsure2026

Awesome thank you! So this one should be ok for drywall and wood? It just doesn’t say in the description 🙂 @MitchellMc

MitchellMc

Drywall and wood are not listed as it's typically used around direct wet areas and fixtures @notsure2026. However, you're applying it to a painted surface, such as the drywall and timber, which I believe is fine. It might actually be exposed timber in the gap. Silicone sticks to just about anything, so it should be all good.

Let me tag @Nailbag for his thoughts. My only concern is using a standard gap filler in a bathroom if you are not going to paint over it.

Mitchell

notsure2026

Thanks @MitchellMc - it is the lengthwise edge above the bath and does not necessarily get hit with water directly (provided there is no splashing)

MitchellMc

The reason I'm second-guessing myself is that recently I caulked a couple of bathrooms around the ceilings, walls and windows with Selleys 475g No More Gaps Interior Multipurpose Gap Filler. They were not in immediate wet zones, similar to your situation. However, after completing the job, I was thinking to myself, should I have used a dedicated wet-area silicone sealant? I think I'm just being over-cautious, and unless it's in a shower recess or a joint that will experience regular wetting, the standard filler linked here is sufficient, even without painting it. It does state in the technical data that it is not suitable for submersion or constantly damp areas, which would not be the case with your windows.

I'd go with the Selleys 475g No More Gaps Interior Multipurpose Gap Filler, which is suitable for drywall, wood and painted surfaces.

Mitchell

Nailbag

Hi @notsure2026

In the end with his last post @MitchellMc in my mind answered his own question. I use the "wet area" silicons for actual surfaces that could be subject to water like edges of tiles, shower glass, matters, basins and benchtops. For other areas around widow arc's, timber trims etc I use a flexible internal gap filler. The type will determine if I need to paint over it as most can't. This one can. Otherwise the Selleys 475g No More Gaps Interior Multipurpose Gap Filler he mentioned is great.

Nailbag

notsure2026

Thank you @Nailbag @MitchellMc

Would this one also be ok to use?

MitchellMc

Yes, it would be @notsure2026. In fact, I hadn't seen it as it's a new product. Likely manufactured for the exact issue discussed above, it's an in-between product for damp areas that are not specifically wet zones. Good find.

Mitchell

notsure2026

Perfect. Thank you!

Nailbag

Yes @notsure2026 and it’s paintable 👍

Nailbag

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