The Tradie’s Guide to Soudal Expanding Foam

For professional builders in Australia, using high-quality expanding foam for insulation and soundproofing is standard practice. But many foams can fail in critical areas exposed to movement, compromising your whole thermal and acoustic barrier.

This guide explores the Soudal expanding foam range and why it’s the go-to choice for many local pros. We focus on the need to choose the right product for each project, guaranteeing your seals last long-term and deliver solid performance.

Key Takeaways

• Gap Type Selection: Use standard PU foam for stable, non-moving voids and filling. Switch to Flexifoam for joints subject to movement and thermal expansion to prevent internal cracking and maintain performance.
• Pro Performance: Flexi Foam is tested up to 9,000 flexes and provides 60dB/STC 61 acoustic value. Soudafoam FR HY provides up to 240 minutes of fire retardancy.
• Application Integrity: Use the Foam Gun system to control expansion and prevent the non-UV resistant foam from being exposed and losing integrity.

What is Expanding Foam? The Science Behind Thermal and Acoustic Barriers

Soudal expanding foam is a high-performance Polyurethane (PU)-based solution, chosen for superior thermal and acoustic barriers and gap filling. This PU expanding foam creates airtight seals that are essential for draft-proofing and insulation, helping to create a warmer, drier, healthier building.

The Critical Difference: Static vs. Dynamic Gaps

Don’t make the mistake of treating all gaps the same. The expanding foam you choose must be based on movement.

• Static Gaps: Use standard polyurethane foam for rigid, non-moving fills like pipe penetrations or general gap filling. This foam is designed to cure dense and hard, providing stable support and basic insulation in environments free from vibration.
• Dynamic Gaps: Requires a highly flexible foam for areas exposed to movement or vibration, such as window or door frames. The foam must have high elasticity to absorb movement and prevent seal failure over time.

The problem with rigid foam in dynamic joints is that it lacks the flexibility needed to absorb movement, causing internal breakdown inside the foam mass. This loss of integrity dramatically reduces its ability to insulate sound effectively. For instance, this failure in a 90mm deep hole can lead to a significant acoustic loss, such as a drop from 44dB to 32dB.

The Soudal Expanding Foam Range: Matching Foam to the Job

Stop wasting time and money on call-backs. The key to a high-performance job is simple: match the right Soudal expanding foam to the specific job, whether it’s fire rating, movement, or general gap filling.

Flexible Solutions for Movement

When a job requires more than general gap filling, Soudal offers specialised performance. For dynamic areas like window and door frames, use Flexible Insulation Expanding Foam to accommodate movement, preventing cracking while providing reliable thermal and acoustic insulation.

Low-VOC Solution for Healthy Homes

For environmentally conscious projects, Soudafoam SMX Expanding Foam is the top-tier solution. As a low-VOC and isocyanate-free foam, it is ideal for healthy home projects. Crucially, it offers up to 3x more flexibility than standard PU foam, guaranteeing both airtight seals and long-term durability against movement.

Fire-Rated Foams for Certified Performance

For applications requiring certified fire resistance, Soudafoam FR HY Expanding Foam is the professional choice. This foam provides high filling capacity, excellent adhesion, and ensures compliance. 

General Gap Filling and Application Systems

The versatile Gap Filling Expanding Foam is available in three formats to match any application size and required precision. The Genius Gun offers excellent one-handed control and is reusable for up to 6 weeks. The basic Straw format is a ready-to-use option for quick, smaller applications. Finally, the Gun Grade, designed for the Compact PU Foam Gun, provides the precision and control needed for high-volume tasks like insulating wall cavities and roof voids.

Real-World Performance: The Waikato Regional Theatre Case Study

When Foster Construction set out to deliver the Waikato Regional Theatre, a complex $80m venue designed for world-class acoustic quality, they didn’t choose standard sealants. They partnered with Soudal to provide a unique, high-performance solution

Solving the Movement Challenge

Soudal’s expanding foam was strategically chosen to handle the continuous expansion and contraction of massive structural panels on this complex build. This selection was critical because standard rigid foams would immediately disintegrate under the constant stress. The foam’s high flexibility maintained its integrity, ensuring a superior, enduring acoustic seal throughout the structure.

Proof of Flexibility and Durability

The flexible foam maintained the vital acoustic comfort and thermal barrier by moving with the building, providing the long-term durability demanded by the project’s unique challenges near dynamic environments.

Precision and Quality

Applicators also benefited from the foam’s tighter cell structure and a controlled 30-40% post-expansion rate. This allowed for greater accuracy and less waste during application than traditional, over-expanding rigid foams.

Best Practices: Application, Layers, and Common Mistakes

The best foam in the world can still fail if you don’t nail the application. Let’s walk through the prep, layering, and common mistakes that separate a lasting seal from a costly call-back.

• Preparation: Always clean the application area and moisten porous surfaces (like timber or concrete) before use for better adhesion and optimal foam expansion.
• Technique: Apply in small layers for optimal coverage and uniform cell structure. Foams like Soudafoam SMX benefit from layered application, especially in deep joints (max 75 mm per layer).
• Mistakes to Avoid: Don’t use standard, rigid foam in dynamic joints; it causes internal breakdown and severe acoustic/thermal performance loss. Don’t leave cured foam exposed without an over-coating, as it is not UV resistant and will lose integrity. Use PU Foam Remover to immediately clean uncured foam.

From Static Gap to Sound Transmission Class 61 with Soudal Expanding Foam

The key to mastering expanding foam for soundproofing and insulation is matching the foam to the gap’s movement level. Flexible insulation Expanding Foam is essential for dynamic environments, while the Soudafoam FR HY line covers every compliance need.

By choosing Soudal expanding foam, backed by proven performance on complex projects, you ensure the highest quality finish and long-lasting results.

Explore Soudal’s expanding foam solutions and find your nearest stockist today.