Everything you need to know: Sealants

Sealants are the unsung heroes of the DIY world. Whether you're renovating a bathroom, fitting a kitchen, or sealing up gaps around your windows, choosing the right type of sealant can make all the difference. Depending on your chosen sealant, it can keep out water, air, dust, and even mould - and gives your project a neat, professional-looking finish. 

In this guide, we’ll break down what sealants are, why you need them, the types available, and how to apply sealants correctly to get the best results. 

A sealant is a flexible material used to block the passage of liquids, air, or other substances through joints, gaps, or openings. Think of it as the final touch that seals and protects your work. 

Unlike adhesives (which are mainly used to bond materials), sealants are all about creating watertight or airtight barriers - while allowing some flexibility for movement. 

Interested in grab adhesives? Discover our article on everything you need to know about grab adhesives. 

Sealants are important for many reasons, including: 

Water protection 

• Sealants are essential in moisture-prone areas like bathrooms and kitchens to stop leaks, drips, and water damage. 

Air tightness 

• Used around windows, doors, and pipework, sealants help improve insulation by blocking drafts and air leaks. 

Flexibility 

• Most sealants remain flexible after curing, which is perfect for areas where materials expand and contract with temperature changes. 

Mould resistance 

• Special formulations contain fungicides that resist mould growth in damp areas, keeping everything clean and hygienic. 

Fill gaps and cracks 

• Some sealants are excellent for filling small gaps and hairline cracks in walls, joints, or trims - helping create a smooth, seamless finish and preventing dust or moisture from getting in. 

Not all sealants are the same. Here's a rundown of the most common types you'll find on the shelves, including recommendations from EVO-STIK: 

Sanitary sealants 

Sanitary sealants, also known as sanitary silicones, are specially designed for wet areas like bathrooms or kitchens. 

• Best for: Bathrooms, showers, sinks, and kitchens 
• Features: Mould-resistant, waterproof, designed for constant moisture exposure 

Recommended product(s): EVO-STIK Bathroom & Kitchen Sealant, EVO-STIK Stops Mould Dead Sealant, EVO-STIK White for Life Sealant, EVO-STIK Clear for Life Sealant or EVO-STIK 1 Hour Shower & Bathroom Sealant. 

Tip: Always check the label for “mould-resistant” or “anti-fungal” properties. 

All purpose sealants

All purpose or multipurpose silicone sealants provide versatility for a range of interior and exterior jobs. 

• Best for: Windows, doors, skirting, expansion joints, and general gap filling 
• Features: Weatherproof, UV resistance, flexible, and some can be painted over where necessary 

Recommended product: EVO-STIK All Purpose Sealant - to create a tough, resilient, long-lasting seal on most applications. 

Tip: A reliable all-rounder, this type of sealant is ideal to keep on hand for general maintenance and unexpected DIY tasks.

Application-specific sealants 

Specialist sealants are formulated for specific environments or performance requirements. These include sealants designed for window and door frames, filling gaps, to cure within a particular timeframe and more.

Window and door frame sealants are designed to handle movement and exposure to the elements while keeping gaps sealed. 

• Best for: High-temperature areas, glazing, and joints exposed to moisture or other elements 
• Features: Tailored properties like moisture resistance, heat resistance or UV stability 

Decorator’s Caulk is designed for interior finishing work as its perfect for filling small gaps and cracks before painting and decorating. 

• Best for: Skirting boards, coving, ceiling corners and small wall cracks 
• Features: Quick-drying, paintable, smooth finish 

Recommended product: EVO-STIK Window & Door Frame Sealant and EVO-STIK Decorator’s Caulk. 

Tip: Always match the sealant’s specification with the project’s technical needs.

What you will need: 

• Your chosen sealant 
• Caulking gun 
• Utility knife 
• Smoothing tool 
• Cloth or sponge 
• Gloves 
• Cleaning solvent (for solvent-based adhesives) 

Optional: 

• Safety goggles 
• Masking tape 

Clean both surfaces thoroughly. Remove any dust, grease, or debris. For best results, surfaces should be dry. 

Carefully cut off the dome of the cartridge, taking care not to damage or shorten the thread. 

Tip: Use masking tape to get a clean, straight line. This is especially useful around baths and basins for a professional-looking finish. 
 

Screw the sealant nozzle onto the cartridge and cut off the tapered end at a 45° angle, to a width matching the gap to be sealed. Then, insert the cartridge into the cartridge gun and repeatedly squeeze the trigger until the sealant appears. 

Place the nozzle at the start of the gap and gently squeeze the trigger to run a steady, even bead along the joint. Push forward slowly, ensuring contact is made by the sealant with both sides of the gap. 

Tip: When applying the sealant, work slowly and keep consistent pressure on the trigger to avoid lumps or gaps. 

Before it skins over, smooth the sealant using a wet, dedicated smoothing tool - do not use a wetted finger. Using a wetted finger may introduce bacteria into the uncured sealant which can affect the finish and lifespan of the sealant. However, smoothing the sealant with a tool will push the product into the joint and give a neat finish. 

Wipe away any excess sealant immediately with a cloth. Use water for water-based products or the recommended solvent such as white spirit, for solvent-based ones. 

Then, carefully pull the masking tape away while the sealant is still wet. Wipe away any excess sealant from the nozzle.

Check the sealant’s instructions for full curing time. While many sealants skin over in minutes, full cure is often reached in 24-48 hours. 

• Don’t apply on wet or dirty surfaces. It weakens the bond and may cause mould. 
• Don’t skip masking tape. It makes a huge difference for neatness, especially as a beginner. 
• Don’t overwork the bead. Too much tooling can mess up the smooth finish. 
• Don’t rush the curing. Wait the full recommended time before using the sealed area, especially in wet zones.
• Check if the sealant can be painted. Generally, acrylic and MS Polymer sealants can be painted, but silicone sealants cannot.

Sealants are simple to use but incredibly effective in protecting your home from moisture, air leaks, and mould. By choosing the right sealant for your job - be it a sanitary silicone for the bathroom or a multipurpose option for general projects around the home - you’ll get results that last and look great.