When choosing the best adhesive for waterproof sealing, it’s important to select a product that provides both strong bonding and long-term resistance to water, weather, and temperature changes. Not all adhesives are designed to seal against moisture, and using the wrong type can lead to leaks, bond failure, or corrosion over time.
In this guide, we compare the most reliable waterproof adhesives available in the UK, including Plexus, Permabond, HB42, Adflex, Adshead Ratcliffe, and Bostik products, and explain when each should be used. If your application involves bonding different materials, see our strongest glue for metal to plastic guide for high-strength waterproof solutions.
For a general overview of sealant types and waterproof bonding materials, this technical guide explains the differences between silicone, polyurethane and hybrid sealants:
https://www.chemsealant.com/news/the-ultimate-guide-to-sealant-types-applications-and-benefits/
What Makes the Best Adhesive for Waterproof Sealing?
The best adhesive for waterproof sealing should have:
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Strong adhesion to multiple materials
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Resistance to moisture and humidity
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Flexibility to allow movement
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Good gap-filling properties
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Long-term weather resistance
Hybrid polymers, methacrylate adhesives, epoxies and polyurethane sealants are commonly used because they can maintain strength even when exposed to water. For a full comparison of adhesive types, read our epoxy vs MMA vs PU adhesive guide to understand how each performs in wet environments.
1. Hybrid Polymer Sealants (Best All-Round Waterproof Adhesive)
Hybrid polymer adhesives are often the best adhesive for waterproof sealing where flexibility and weather resistance are required.
Recommended Products
HB42 Ultimate Sealant & Adhesive
Strong hybrid polymer adhesive with excellent waterproof sealing and flexibility.
Best for: metal, aluminium, steel, glass, wood, PVC, GRP, concrete, ceramics, painted surfaces
Buy here: HB42 Ultimate Adhesive & Sealant – High Grab Hybrid Polymer (All Colours)
Adflex High-Performance Polymer Adhesive
Flexible polyurethane / polymer adhesive suitable for waterproof sealing and structural joints.
Best for: metal, steel, aluminium, concrete, wood, GRP, PVC, composite panels
Buy here: Polyurethane Sealant & Adhesive – High Strength Flexible PU (Adflex)
Arbo Arbosil HM Sealant (High Modulus Silicone)
High modulus silicone sealant ideal for waterproof joints and exterior sealing.
Best for: glass, aluminium, steel, ceramics, sanitaryware, PVC, glazing systems
Buy here: Arbo Arbosil HM Sealant 310ml – High Modulus Silicone Sanitary Sealant
ARBOBOND Pro Universal Adhesive
Hybrid polymer grab adhesive suitable for strong bonding and waterproof sealing on building materials.
Best for: metal, brick, block, concrete, wood, plasterboard, PVC, damp surfaces
Buy here: ARBOBOND Pro Universal Adhesive 290ml – Hybrid Polymer Grab Adhesive
Why Hybrid Polymers Work Well
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Excellent waterproof sealing
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Flexible after curing
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Good adhesion to metal, plastic, glass and concrete
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Suitable for indoor and outdoor use
Hybrid polymer sealants are widely used in construction because they combine the strength of adhesives with the sealing ability of silicone. If you’re unsure when to use hybrid adhesives, our hybrid polymer vs PU vs silicone guide explains the key differences.
2. Structural MMA Adhesives (Best for Permanent Waterproof Bonding)
When maximum strength is required, structural methacrylate adhesives are often the best adhesive for waterproof sealing in industrial applications.
Recommended Products
Plexus MA310 Structural Adhesive
High-strength MMA adhesive suitable for marine, automotive and composite bonding.
Best for: aluminium, steel, GRP, ABS, PVC, acrylic, composite panels
Buy here: Plexus MA310 Methacrylate Structural Adhesive – 50ml Cartridge
Permabond TA4611 Acrylic Adhesive
Designed for bonding plastics and metals where moisture resistance is required.
Best for: polypropylene (PP), polyethylene (PE), HDPE, nylon, aluminium, stainless steel
Buy here: Permabond TA4611 Acrylic Adhesive 25ml – Polyolefin & Plastic Bonding
If you’re working with difficult plastics, our best adhesive for plastic to plastic guide explains the best solutions.
Why MMA Adhesives Work for Waterproof Sealing
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Very strong bond
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Good chemical resistance
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Resistant to moisture and vibration
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Suitable for dissimilar materials
These are often used in marine, automotive and engineering environments where both strength and sealing are required. For more detail on structural bonding, see our structural adhesives UK guide.
3. Epoxy Adhesives (Best for Rigid Waterproof Repairs)
Epoxy adhesives provide excellent strength and chemical resistance, making them a good choice when a rigid waterproof bond is needed.
Recommended Product
Permabond ET500 Epoxy Adhesive
Fast curing structural epoxy adhesive suitable for high-strength waterproof bonding.
Best for: aluminium, steel, stainless steel, composites, GRP, carbon fibre, rigid plastics, ceramics
Buy here: Permabond ET500 Epoxy Adhesive 50ml – Fast Cure Structural Epoxy
When to Use Epoxy
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Metal repairs
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Structural bonding
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Chemical exposure
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Rigid assemblies
Epoxy adhesives cure into a solid, waterproof bond and are often used in engineering repairs.
For more information read our guide Epoxy vs MMA vs PU Adhesive – Which Structural Adhesive Should You Use?
4. Flexible Sealant Adhesives (Best for Joints & Movement)
For sealing gaps, joints, roofing, or panels, flexibility is more important than strength.
Recommended Product
Arbomeric MP20 Hybrid Sealant
Flexible modified polymer sealant suitable for waterproof sealing, glazing and construction joints.
Buy here: ARBO Arbomeric MP20 Anti Pick Sealant 380ml
This is ideal for:
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Roof sealing
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Bathroom sealing
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Exterior joints
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Metal panels
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Plastic housings
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Windows and glazing
Flexible adhesives allow expansion and contraction without cracking, which is essential for waterproof sealing. For more sealing applications, see our ARBO sealants UK guide covering glazing, construction and waterproof joints.
Adhesive Comparison Chart
| Adhesive | Type | Strength | Flexibility | Best Use |
|---|---|---|---|---|
| HB42 | Hybrid polymer | ⭐⭐⭐⭐☆ | ⭐⭐⭐⭐⭐ | Waterproof sealing & bonding |
| Adflex | MS polymer | ⭐⭐⭐⭐☆ | ⭐⭐⭐⭐⭐ | Flexible waterproof joints |
| Plexus MA310 | MMA | ⭐⭐⭐⭐⭐ | ⭐⭐⭐⭐☆ | Structural waterproof bonding |
| Permabond TA4611 | Acrylic | ⭐⭐⭐⭐⭐ | ⭐⭐⭐⭐☆ | Plastic / metal waterproof bond |
| Permabond ET500 | Epoxy | ⭐⭐⭐⭐☆ | ⭐⭐⭐☆☆ | Rigid waterproof repairs |
| Bostik sealants | Hybrid / epoxy | ⭐⭐⭐⭐☆ | ⭐⭐⭐⭐☆ | General waterproof bonding |
| Arbo sealants | Hybrid / silicone | ⭐⭐⭐⭐☆ | ⭐⭐⭐⭐⭐ | Construction sealing |
If your application involves sealing materials, our best adhesive for EPDM rubber guide explains how different adhesives perform.
Choosing the Best Adhesive for Waterproof Sealing
The best adhesive for waterproof sealing depends on the application:
| Application | Best choice |
|---|---|
| Flexible joints | HB42 / Adflex / Arbo |
| Structural bonding | Plexus / Permabond |
| Rigid repair | Epoxy |
| Outdoor sealing | Hybrid polymer |
| Plastic to metal | MMA adhesive |
| Marine / wet areas | Hybrid or MMA |
Surface Preparation Tips
To get the best results:
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Clean surfaces with IPA
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Remove grease and dust
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Lightly abrade smooth metal
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Clamp if required
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Allow full cure time
Even the best adhesive for waterproof sealing will fail if surfaces are not prepared correctly.
Final Recommendation
For most applications, hybrid polymer adhesives such as HB42 or Adflex are the best adhesive for waterproof sealing where flexibility is required.
For high-strength or structural bonding, products like Plexus MA310, Permabond TA4611 or ET500 provide superior durability.
For repairs or rigid joints, epoxy adhesives remain one of the most reliable waterproof bonding solutions. For more technical advice, explore our adhesive advice & technical guides covering bonding, sealing and material selection.