Sealants stop water getting where it shouldn't. Use the wrong one and it'll fail, go mouldy, or not stick. Here's what actually works where.
The Main Types
Silicone Sealant
What it is: Flexible, waterproof, long-lasting
Use for:
- Bath/shower to wall joints
- Around sinks and basins
- Where tiled surfaces meet sanitaryware
- Any joint that needs to stay waterproof
Pros: Very waterproof, flexible, durable Cons: Can't be painted, needs surfaces very clean to adhere
Sanitary Silicone
What it is: Silicone with added anti-mould agents
Use for:
- All bathroom applications
- Anywhere humidity is high
- Around baths, showers, toilets, sinks
Pros: Resists mould growth (for a while) Cons: Anti-mould eventually wears off
Decorator's Caulk
What it is: Acrylic-based, paintable filler/sealant
Use for:
- Gaps between walls and woodwork
- Filling before painting
- Non-wet areas
Pros: Paintable, easy to apply, cheap Cons: NOT waterproof - useless in wet areas
Frame Sealant
What it is: Flexible exterior-grade sealant
Use for:
- Window and door frames
- Exterior joints
- Where movement is expected
Pros: UV stable, weatherproof Cons: Not for interior sanitaryware
Where to Use What
| Location | Best Sealant |
|---|---|
| Bath to wall | Sanitary silicone |
| Shower tray to tiles | Sanitary silicone |
| Around kitchen sink | Sanitary silicone |
| Worktop to wall | Kitchen/bath silicone |
| Skirting to wall | Decorator's caulk |
| Door frame to wall | Decorator's caulk |
| Window frame exterior | Frame sealant |
| Toilet to floor | Sanitary silicone |
My Recommendations
Best All-Round Bathroom: Dow Corning 785+
What it is: Professional-grade sanitary silicone
Why it's good:
- Excellent adhesion
- Good anti-mould protection
- Lasts well
- Trade product = proven quality
Price: ~£8-£10 per tube
Best Budget: UniBond Anti-Mould
What it is: Consumer sanitary silicone
Why it's good:
- Widely available (supermarkets even)
- Decent quality for the price
- Good enough for most DIY applications
Price: ~£5-£7 per tube
Best for Kitchens: Everbuild Forever White
What it is: Silicone designed for kitchens
Why it's good:
- Stays white (doesn't yellow)
- Good for worktop to wall joints
- Food-safe when cured
Price: ~£6-£8 per tube
Best for Tricky Colours: CT1
What it is: Universal sealant/adhesive
Why it's good:
- Works on everything
- Many colours available
- Very strong adhesion
Price: ~£12-£15 per tube
Note: CT1 is expensive but useful for problem applications.
Colour Choices
White: The standard. Works most places.
Clear: Good for glass shower screens, when you want joint invisible.
Grey: Popular modern choice, hides dirt better than white.
Brown: For matching wooden worktops or frames.
Black: Contemporary look, often for shower trays.
Match tiles: Some brands offer tile-matching colours.
Application Tips
Preparation is Everything
The single biggest factor in sealant success:
- Remove all old sealant - Completely. No residue.
- Clean with appropriate cleaner - Methylated spirit works well
- Dry thoroughly - Silicone won't stick to wet surfaces
- Mask edges - Gives clean lines, easier cleanup
Applying the Bead
- Cut nozzle at 45 degrees, appropriate size (not too big)
- Apply steady pressure, move at consistent speed
- Overlap slightly with masking tape
- Tool immediately while still wet
Tooling
Options:
- Wet finger (traditional, works fine)
- Sealant tool (plastic profile tool)
- Wet spoon back (old decorator's trick)
Tip: Keep a bowl of soapy water nearby. Dip finger/tool to prevent sticking.
Curing
Most silicones:
- Skin time: 10-20 minutes (don't touch)
- Full cure: 24-48 hours (don't get wet)
Check the tube - some quick-cure products are faster.
Common Mistakes
1. Not Removing Old Sealant
New silicone doesn't stick to old silicone. It'll peel off within months.
2. Surface Not Clean/Dry
Grease, soap scum, moisture - all prevent adhesion.
3. Too Much Sealant
A thick bead looks messy and doesn't seal better. Thin, consistent bead is best.
4. Using Caulk in Wet Areas
Decorator's caulk is NOT waterproof. It'll fail and grow mould.
5. Tooling Too Late
Once silicone skins over, you can't smooth it. Work quickly.
6. Getting Wet Too Soon
48 hours minimum before showering on new sealant.
When to Replace
Signs sealant needs replacing:
- Black mould you can't clean off
- Peeling or lifting edges
- Discolouration that won't clean
- Cracks or gaps appearing
- Water getting behind tiles
Typical lifespan: Good quality sanitary silicone should last 5-10 years. Cheap stuff or poor application might fail in 2-3.
Removing Old Sealant
Tools:
- Stanley knife
- Sealant remover tool
- Sealant dissolver (optional)
- Scrapers
Method:
- Score along edges with knife
- Pull strip away (often comes in one piece if lucky)
- Scrape residue
- Use dissolver for stubborn bits
- Clean thoroughly before re-sealing
Need sealing done properly? I re-seal bathrooms and kitchens across Exeter. Call 01392 964094 or get a quote.
Sam Hembury
Sam is the founder of Hembury Contracting, providing professional handyman services across Exeter and Devon. With years of experience in property maintenance, he shares practical tips to help homeowners tackle common tasks.
