Description
3H Perforated Sand Underlay Roofing Felt – 20m x 1m | Glass Fibre Mineral | Ventilated Roofing Underlay
Improve the performance and ventilation of your roofing system with 3H Perforated Sand Underlay Roofing Felt, a high-quality ventilated roofing membrane designed for use as the underlay layer within a 2-layer flat roofing system. Manufactured with a durable glass fibre mineral construction, this sand-backed underlay provides reliable support, strength and long-lasting performance beneath the final roofing layer.
Featuring a perforated design, this roofing underlay allows improved ventilation within the roof structure, helping to manage moisture and support the overall performance and longevity of the roofing system. The sand-backed surface provides excellent compatibility with installation methods including torching on and pour and roll applications.
Supplied in a 20m x 1m roll, this charcoal mineral underlay is suitable for professional roofing applications where a dependable and breathable base layer is required.
Product Features
- Premium 3H perforated sand underlay roofing felt
- Designed for use as an underlay in a 2+ layer roofing system
- Glass fibre mineral reinforced construction
- Sand-backed finish for installation compatibility
- Perforated design for improved ventilation efficiency
- Suitable for torch-on and pour-and-roll installation methods
- Durable and flexible roofing solution
- Charcoal mineral finish
- Suitable for professional roofing applications
Technical Specifications
Product: 3H Perforated Sand Underlay Roofing Felt
Roll Size: 20m x 1m
Weight: 36kg per roll
Construction: Glass Fibre Mineral
Backing: Sand-backed
Colour: Charcoal
Installation Method: Torch-on / Pour and Roll
Application: Underlay in a 2+ layer roofing system
Life Expectancy: 10+ years when installed as part of a 2-layer system
Recommended Applications
The 3H Perforated Sand Underlay is ideal for use in:
- Flat roofing systems
- Built-up roofing applications
- Two-layer felt roofing systems
- Commercial roofing projects
- Domestic flat roof installations
- Refurbishment and new roofing projects
Installation Advice
For the best results:
- Always unroll and line up the product, allowing the membrane to settle before rolling it back up and applying heat.
- Lay the underlay loosely during installation to maximise ventilation efficiency.
- Ensure the product is installed correctly as part of a suitable multi-layer roofing system.
Why Choose 3H Perforated Sand Underlay?
The 3H Perforated Sand Underlay Roofing Felt provides a reliable foundation layer for flat roofing systems, combining glass fibre reinforcement, ventilation performance and installation versatility. Designed to work beneath a compatible cap sheet, it helps create a durable roofing system with a life expectancy of 10 years or more when correctly installed as part of a 2-layer application.
Ideal for roofing contractors and professional installers, this ventilated underlay offers a practical solution for creating strong, efficient and long-lasting flat roofs.


