Whether you’re a seasoned tradie or just starting out, using the right sealant for the job isn’t just best practice. It’s essential for guaranteeing a durable result that won’t lead to costly call-backs. But with so many products on the shelf, knowing which one is up to the task isn’t easy.
This guide shares the 6 types of sealants you need to know. We’ll break down the features, use cases, and benefits of each, so you know which Soudal sealant is best for your next construction project.
Key Takeaways
- Successful sealing requires knowing that each of the 6 sealant types has a unique purpose. Correct selection ensures long-term durability.
- Hybrid polymer sealants are the modern solution for tradies, delivering superior versatility, high adhesion, flexibility, and paintability.
- Project compliance and safety rely entirely on selecting the right product, such as a fire retardant sealant for integrity or a polyurethane for structural load-bearing.
1. Silicone Sealants
Definition: These are permanently elastic, high-performance sealants based on silicone polymers. They cure by reacting with moisture in the air.
Uses: Silicone is your go-to when you need a long-lasting, flexible, and waterproof seal. Ideal for bathrooms, kitchens, windows, door frames, and roofing where UV exposure is high.
Benefits:
- Superior flexibility and elasticity to handle high joint movement.
- Excellent moisture and UV resistance for outdoor and wet areas.
- Sanitary formulations offer effective anti-mould properties.
Limitations: Not paintable and require a dry surface for application.
Product Recommendation:
- For general purpose indoor/outdoor sealing:
All Purpose Silicone Sealant
- For professional wet areas:
Bathroom & Kitchen Silicone Sealant
- For metal roof and flashing applications: Roof & Gutter Silicone Sealant
2. Acrylic Sealants
Definition: Acrylic sealants are water-based gap-fillers. They cure as the water evaporates, resulting in a firm seal.
Uses: Suited to both interior and exterior sealing, filling small gaps (up to 5m) around skirting boards, plasterboard, and window frames before painting. Acrylic sealants are the key to a perfect painted finish.
Benefits:
- Easy to apply and clean up (water-based).
- Excellent paintability, often with a smooth, professional finish.
- Low odour, making them safe for occupied interior spaces.
Limitations: Less flexible than silicone or hybrids, and not suitable for areas with continuous water immersion or high joint movement.
Product Recommendation:
- For easy indoor filling that needs painting:
Fill & Paint Gap Filler
- For easy indoor filling that needs painting:
- For exterior filling that’s flexible and paintable:
All Weather Flex Gap Filler
3. Hybrid Polymer Sealants
Definition:
This advanced
type of sealant
combines the best of silicone (flexibility, UV resistance) and polyurethane (strength, paintability) into a superior, solvent-free product built on SMX technology.
Uses: Where you need high adhesion and flexibility. Hybrid polymer sealants are perfect for bonding, heavy-duty construction, weatherproofing, and all-purpose sealing where the joint needs to be painted.
Benefits:
- Extremely high adhesion even to damp surfaces.
- Paintable and solvent-free for low odour.
- Fast-curing options are available.
Limitations: Generally more expensive than basic acrylic or silicone.
Product Recommendation:
- For extreme initial grab and heavy structural bonding:
Fix ALL High Tack
- For crystal clear sealing and bonding:
Fix ALL Crystal
- For rapid curing speed: Fix ALL Turbo
- For vertical joints requiring a non-slump, high flexibility seal: Multibond SMX25
- For trafficable joints carrying both foot and vehicle traffic: Multibond SMX50
For more on our Hybrid Polymer range and how it can level up your results and streamline your workflow, check out our article: 10 Benefits of Hybrid Polymer Adhesives for Construction
4. Polyurethane Sealants
Definition: PU sealants are high-strength, moisture-curing sealants known for their powerful adhesion and durability, often used in structural applications.
Uses: Ideal for heavy-duty applications like sealing concrete joints, flooring, and metal-to-metal bonding. Polyurethane sealants are the pro’s choice when the bond needs to handle significant mechanical load and abrasion.
Benefits:
- Good structural adhesion and high tensile strength.
- Excellent resistance to chemicals and abrasion.
- Good for high movement joints in concrete.
Limitations: Have a stronger odour than hybrids and require more careful application to prevent shrinkage.
Product Recommendation:
- For easy application, UV resistance and permanent elasticity: Soudaflex 45FC
- For concrete and expansion joints requiring high movement: Soudaflex 20LM
- For self-levelling, professional sealing of horizontal joints and floors: Soudaflex 33SL
5. Fire Retardant Sealants
Definition: These sealants are formulated to resist the passage of fire, smoke, and heat through gaps and service penetrations in fire-rated walls and floors, ensuring compliance with building codes.
Uses: Fire retardant sealants are essential for maintaining the integrity of fire compartments. Use them around pipes, cables, ventilation, and linear joints in fire-rated walls, ceilings, and floors.
Benefits:
- Compliant with fire safety regulations.
- Restores the fire rating of the structure after services are installed.
- Prevents the spread of smoke, which is often more dangerous than the fire itself.
Limitations: Must be used precisely according to fire test data and manufacturer specifications to guarantee performance. Always confirm with your fire engineer before using.
Product Recommendation:
- For sealing applications requiring high temperature resistance: Silirub HT°-A
- For fire-rated gap-filling around penetrations using a foam: Soudafoam FR HY
6. Construction Foams
Definition: Think of construction foams as gap-fillers rather than typical elastic sealants. These polyurethane foams expand to fill and insulate, they’re absolutely key for crucial thermal and acoustic sealing.
Uses: Perfect for filling large, odd-shaped gaps around window and door frames, sealing service penetrations, insulating roof and wall cavities, and soundproofing partitions.
Benefits:
- High expansion rate fills large voids quickly.
- Provides excellent thermal insulation and acoustic dampening.
- Easy and fast application via straw or genius gun.
Limitations: Requires proper trimming after curing; surfaces must be moistened for best expansion and cell structure; Must be painted over if exposed to UV.
Product Recommendation:
- For quick and easy filling of gaps, joints and holes: Genius Gun Gap Filler Foam
- For sealing joints that require movement: Genius Gun Insulation Expanding Foam
Choosing the Best Sealant for Construction Projects
Understanding these 6 types of sealants is the first step to delivering solid results on site. You wouldn’t use a screwdriver for a nail, and you shouldn’t use silicone where a strong hybrid or PU is required. Choosing the right sealant type, from flexible silicone, strong polyurethane, or versatile hybrid polymer, ensures long-lasting protection and efficient workflows.
To ensure success on every job, explore the full range of Soudal sealants and find your local stockist today.
Plus, for more on-site hacks and specialist tips, explore our guide: How to Apply Silicone Sealant Neatly.