Description
Need expanding foam without damaging frames or over-expanding?
Standard expanding foams can expand aggressively, causing warping, distortion, and messy overfill — especially around window and door frames.
The HB42 Low Expansion LXP Foam is specifically designed for controlled application, giving you precise filling, strong adhesion, and insulation without the risk of excessive expansion.
Why choose low expansion foam?
Unlike standard PU foams, this formulation expands only up to 2x its original volume, making it ideal for:
- Installing window and door frames without distortion
- Filling gaps where precision is critical
- Sealing cavities without creating excess waste
- Reducing clean-up and trimming time
👉 Perfect for professional installers and high-quality finish work.
Ideal applications
This foam is commonly used for:
- Window and door frame installation
- Sealing gaps around frames and panels
- Insulating cavities, cracks and voids
- Filling around pipework, ducting and cables
- General construction and maintenance work
For structural bonding applications, explore our Plexus MMA adhesives
Strong multi-surface adhesion
HB42 LXP Foam bonds to:
- Concrete, brick and stone
- Wood and plaster
- Metals and coated surfaces
- Most plastics
👉 Suitable for construction, refurbishment and repair work.
For sealing and bonding alongside foam, see our HB42 adhesive & sealant range
Designed for control and precision
- ✔ Ultra-low expansion (max 2x volume)
- ✔ Fast tack-free time (~6 minutes)
- ✔ Cuttable in 30–70 minutes
- ✔ High yield (up to 35 litres)
- ✔ Minimal shrinkage (max 5%)
👉 More control, less waste, cleaner results.
Low Expansion Foam vs Standard Expanding Foam
Unlike high expansion PU foam, low expansion foam reduces the risk of frame movement during curing making it suitable for uPVC, aluminium and timber frame installation applications.
| Feature | Low Expansion Foam | Standard Expanding Foam |
|---|---|---|
| Expansion pressure | Low | High |
| Suitable for windows/doors | Excellent | Risky |
| Risk of frame distortion | Minimal | Higher |
| Precision application | Excellent | Moderate |
| Trim waste | Lower | Higher |
Application & performance
- Application temperature: 5°C to 30°C
- Service temperature: 5°C to 30°C
- Fire rating: B3 (DIN 4102)
When should you use this foam?
Choose HB42 LXP Foam if you need:
- A low expansion foam for windows and doors
- A foam that won’t distort frames
- A precise expanding foam for controlled filling
This low expanding foam is ideal for professional window and door installation where controlled expansion is essential.
When NOT to Use Low Expansion Foam
Low expansion foam should not be used:
- where structural load-bearing strength is required
- in continuously submerged environments
- near naked flames or high heat sources
- where UV-exposed foam will remain uncovered long term
Frequently Asked Questions
What is low expansion foam used for?
Low expansion foam is commonly used for fitting window and door frames, sealing cavities, insulating gaps and reducing air leakage without causing frame distortion.
What is the difference between low expansion foam and standard expanding foam?
Standard expanding foams can continue expanding aggressively after application, whereas low expansion foam provides more controlled expansion, making it safer for precision installations.
Can low expansion foam be used around uPVC windows?
Yes, low expansion foam is commonly used around uPVC and aluminium window frames because it reduces the risk of bowing or warping during curing.
Is low expansion foam waterproof?
Once cured, most PU low expansion foams provide good moisture resistance, although they should usually be protected from direct UV exposure externally.
How long does low expansion foam take to cure?
HB42 Low Expansion Foam becomes tack-free in approximately 6 minutes and can typically be cut within 30-70 minutes depending on temperature and humidity.
