Give your home extension the roof it deserves
10 September 2025For many years, flat roofs have been the go-to choice for extensions. They can seem straightforward, and they save on head height where planning restrictions are tight. But flat roofs also come with a reputation: water pooling, leaks, and the constant worry about whether they’ll last the distance. They can even affect your home insurance, as some insurers limit or exclude cover for flat roofs due to the risks.
Flat vs Pitched
For many years, flat roofs have been the go-to choice for extensions. They can seem straightforward, and they save on head height where planning restrictions are tight. But flat roofs also come with a reputation: water pooling, leaks, and the constant worry about whether they’ll last the distance. They can even affect your home insurance, as some insurers limit or exclude cover for flat roofs due to the risks.
Shallow pitch is possible
The good news? You don’t need to compromise. With Onduline’s ISOLINE® LOW LINE sub-roof system, you can now enjoy the benefits of a pitched roof as low as 10 degrees, opening up the freedom to use any roof tile on your extension, without being restricted by manufacturer pitch requirements. ISOLINE® LOW LINE takes care of the waterproofing, leaving the roof tiles to provide the aesthetic finish.
Style that blends seamlessly
One of the biggest frustrations with flat-roof extensions is how different they look compared to the rest of the house. They often stick out, breaking up the character of your home. But ISOLINE® LOW LINE changes that. By creating a secure waterproof layer beneath your roof tiles, it makes it possible to fit any roof tile, even a flat profiled tile, to your house extension, as low as 10 degrees. That means your extension can be finished in the same tiles as your main roof, creating a seamless, consistent look that feels like it was always meant to be there.
Whether you want to match traditional slate, modern concrete tiles, or even reclaimed materials to keep a heritage feel, ISOLINE® LOW LINE gives you that flexibility. It’s about creating harmony, not contrast.
Protection that lasts
Looks aside, a pitched roof simply works harder for your home. Instead of water lingering on the surface, the slope encourages fast drainage, reducing the risk of leaks, dampness, and costly repairs. With ISOLINE® LOW LINE sitting under your chosen tiles, you get an extra layer of reassurance. In fact, it’s the only sub-roof system in the UK to be BRE tested and BBA accredited for pitches as low as 10 degrees, and it comes with a 30-year guarantee. That means you can extend your home with confidence, knowing you’ve chosen a solution designed to last.
Get it right first time
Extending your home is a big investment. Nobody wants to be dealing with roof problems just a few years down the line. Choosing ISOLINE® LOW LINE means you can get it right first time. It’s a smarter, future-proof choice that removes tile-pitch limitations, so your builder can select the tile for appearance while ISOLINE® LOW LINE manages the waterproofing - giving you the freedom to use the look you want without being held back by minimum pitch requirements.
More choice through partnerships
Onduline has also partnered with Northstone Materials to unlock even more possibilities for homeowners and their builders. This collaboration means you have access to a wide range of premium flat roof tiles designed to work perfectly with ISOLINE® LOW LINE, such as its Causeway and Dunluce ranges, ensuring both aesthetic appeal and durability in your extension project.
A better way to extend your home
Your extension should be more than just extra space - it should feel like a natural part of your home. By choosing a pitched roof with ISOLINE® LOW LINE, you can achieve a design that looks better, lasts longer, and gives you peace of mind.
So, before you settle for a flat roof, talk to your builder about ISOLINE® LOW LINE. It’s the smarter way to create an extension that blends style with substance, and a roof that works as hard as the home beneath it.
To learn more about the difference our roofing solutions can make, visit our case studies page.
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