Learn all about our new sub-roofsolution, ISOLINE, which is perfect for low pitched tiles roofs.

For those undertaking a home renovation project, did you know recent changes in planning rules mean home owners will be able to add two extra floors to their houses without needing full planning permission? This news brings an increased demand for low pitched roofing, as homeowners seek to maximise their living space.

If it’s low pitched roofing you’re interested in, you’re going to want to find out about our market-leading underlay system, ISOLINE.

You may already be familiar with our corrugated roofing sheets, we have an extensive range of styles including our CLASSIC sheets, our ONDUVILLA tile strips and BARDOLINE shingles. All of which are perfect for sheds, outbuildings, pergolas, and more but our ISOLINE product is a little bit different!

ISOLINE is a BBA-certified underlay system designed to work as a waterproof layer underneath traditional roof tiles. The goal is to make the pitch as low as possible while retaining the integrity of the roof structure so it remains weathertight. Already an essential for many professional roofers, ISOLINE is a sustainable ‘roof beneath a roof’.


Our ISOLINE LOW LINE system acts as a waterproof barrier underneath your roof to ensure water is kept at bay, preventing any leaks. ISOLINE roofing underlays also meet the ‘green agenda’, as the material is made of a minimum 50% recycled cellulose fibres, contain no asbestos and do not release any hazardous substances. The ISOLINE LOW LINE sheet also benefits from having 24 mm deep corrugations. The low height corrugations make it the ideal sheet for use on low pitched roofs. The LOW LINE sheet is also made up of 21 corrugations, which gives the sheet its maximum rigidity.

Onduline's ISOLINE LOW LINE acting as a waterproof barrier underneath roofing

The ISOLINE LOW LINE underlay sheets work with any type of tiles and will both complement and enhance the performance of your roof. This is especially useful for maintaining the aesthetic of a heritage building.

Ideally used for: very low-pitched roofs on home extensions and heritage sites.

Key ISOLINE benefits

As a quick round-up, here are the key benefits of both of our ISOLINE products:

  • 30-year warranty
  • Easy installation
  • Lightweight and easy to handle and manipulate
  • Suitable for low pitch roofs
  • Watertight acting as a ‘roof under a roof’

As well as our ISOLINE range, you might also be interested to find out more about our ONDUTISS membrane, designed to preserve the waterproofing of roofs and buildings.

Onduline's ONDUTISS membrane preserving the waterproofing of a roof

This BBA-certified permeable roof membrane is made up of three layers, with 100, 120, 140 and 160gsm available. It’s known for its super-strength and resistance to stretching and tearing. Membranes can often suffer from damage during installation on a roof through accidental loads such as tools or falling tiles. Never ideal! Thankfully, the extreme tear resistance of ONDUTISS AIR ensures the highest durability and resilience.

Key ONDUTISS benefits

  • Flexible robust product
  • High vapour permeability
  • Can be used under our corrugated roofing sheets, tile strips and shingles as well as all other roofing materials
  • Fast and easy installation with overlap indicators printed on membranes
  • Can be applied directly to insulation
  • BBA certification

Ideally used for: all types of cold and warm roofing construction.

We hope this introduction to ISOLINE and ONDUTISS will help you along with your roofing project! Our ISOLINE products are perfect for giving you that extra bit of reassurance that your roof will be protected from heavy rainfall as well as maintaining the condition of your roof.

Find out more about our ISOLINE range here and our ONDUTISS membrane here. Our ONDUTISS membrane is also now available to purchase via WICKES!

Discover the full range at onduline.co.uk.

Discover all of our installation guides here.