ISOLINE LOW LINE For Heritage Projects
The Ultimate Under-Roof Waterproofing Solution for Heritage and Listed Buildings
Preserve the Past. Protect the Future.
The Heritage Challenge
Preserving a historic building requires a delicate balance. You need to protect the structure from the elements, yet maintaining the strict aesthetic integrity of traditional tile or slate roofing is non-negotiable.
When a heritage roof begins to leak, standard modern roofing fixes can ruin its historic character. You need a solution that works invisibly behind the scenes.
Meet ISOLINE LOW LINE
ISOLINE LOW LINE is a unique sub-roof corrugated under roofing system designed specifically to act as the primary waterproofing layer beneath traditional tile or slate roofs.
By installing ISOLINE LOW LINE beneath your original roofing materials, you create a dual-layer defence system. Even if the external historic tiles fail, slip, or leak, your building remains watertight.
The Invisible Guardian: ISOLINE LOW LINE allows you to reuse historic, weathered slates or tiles - even those that are slightly compromised - because the waterproofing power sits entirely underneath them.
Why Heritage Projects Choose ISOLINE® LOW LINE
- Preserves Authentic Aesthetics: Because it is installed completely beneath the tiles, the external appearance of the historic roof remains entirely unchanged.
- 100% Watertight Guarantee: Offers a 30-year waterproofing guarantee, ensuring long-term peace of mind for valuable historical interiors and artifacts.
- Enables Lower Roof Pitches: Heritage extensions or restorations often struggle with low pitches. ISOLINE® LOW LINE allows traditional clay tiles or slates to be safely laid on pitches as low as 10°.
- Made from Recycled Fibres: Made from 50% recycled cellulose fibres. It is lightweight, easy to install and adds no significant structural load to aging timber frames.
- Excellent Vapor Permeability: The corrugated profile of the ISOLINE® sheet assists in reducing condensation risk, keeping old roof timbers dry and preventing rot.
How It Works: The Dual-Layer Defence
- The Sub-Roof Barrier: The corrugated bituminous sub-roof sheets are fixed directly to the timber structure.
- The Traditional Overlay: Standard tile battens and the original heritage slates or tiles are fixed over the top.
- The Result: Any water that penetrates the historic tiles is safely caught by the ISOLINE® sheets and channelled directly into the guttering.
Trusted by Heritage Building Professionals
| Feature | Standard Roofing Felt | ISOLINE® LOW LINE |
| Waterproofing Lifespan | Prone to tearing and degradation | 30-Year Guarantee |
| Minimum Roof Pitch | Typically restricted to 20°+ | Safe down to 10° for all tiles |
| Aesthetic Impact | None (hidden) | None (hidden) |
| Timber Protection | Can trap moisture if unventilated | Designed to minimize condensation risk |
Master Heritage Roofing: Book Our CPD
Are you an architect, specifier, or conservation professional looking to deepen your expertise? Join our tailored Continuing Professional Development (CPD) session:
“Advanced Roofing Solutions for Heritage: Balancing Preservation & Performance”
In this seminar, you will learn how to overcome the unique technical challenges of historic properties, navigate strict conservation guidelines, and specify modern sub-roof systems without altering external character.
Restore with Confidence
Don't let leaks compromise history. Protect your heritage project with a hidden waterproofing system that respects the past while utilising modern, reliable engineering.
Expert Guidance
Every heritage project comes with its own unique challenges. Contact Onduline today for personalised technical assistance, specification support, or to discuss how ISOLINE® LOW LINE can be integrated into your next project.