When specifying a rooflight installation, one of the first design decisions to make is whether to choose an on the rafter (standard) or between the rafters (recessed) installation. This choice influences both the aesthetic finish and practical performance of the rooflight within the roofline.
For heritage and listed buildings, the choice is particularly significant. A flush integration helps maintain the building’s traditional appearance while ensuring the installation meets modern performance standards and weather protection requirements.
A rooflight that sits flush within the roofline delivers a professional, long-lasting finish. From both aesthetic and technical perspectives, flush integration enhances the appearance, drainage, and overall durability of the roof.
Before deciding which installation is right for your project, you need to assess your roof build-up.
Roof build-up refers to the total thickness of all layers that sit above the rafters and make up the finished roof structure.
A clay tile roof generally has a build-up of over 100mm, while a slate roof tends to be less than 100mm.
Since most rooflights are approximately 100mm in height, this measurement determines whether your rooflight will sit flush or slightly proud of the roofline.
| Roof Type | Typical Build-Up Height | Recommended Installation |
|---|---|---|
| Clay tiles | 100mm or more | On the rafter (standard installation) |
| Slate tiles | Less than 100mm | Between the rafters (recessed installation) |
A standard installation involves fitting the rooflight directly on top of the rafters, where it sits above the roof structure.
Cavendish House – On the rafter installation, flush with the top of roof tiles.
If your roof build-up measures less than 100mm, such as with slate roofs, a standard installation may result in the rooflight sitting slightly above the roofline. This remains a practical and attractive option, often enhancing visual depth and distinction.
PJ Tonks Studio – On the rafter installation where the rooflight sits slightly proud of the roof surface.
A recessed installation lowers the rooflight between the rafters, supported by bearer beams, allowing the top of the frame to sit level with the roof tiles.
Recessed installations require opening the structural gap wider so the rooflight can drop down between the rafters. The new bearer beams form a sturdy platform for the rooflight frame to rest on.
Our Rooflight Calculator Tool simplifies this process by helping determine the correct dimensions and positioning.
Elmswell / Clayfield – Between the rafters installation, achieving a smooth, flush tile finish.
Choosing the correct installation type depends on your roof build-up and visual design goals. Follow these simple steps:
| Roof Type | Typical Build-Up Height | Recommended Installation |
|---|---|---|
| Clay tiles | 100mm or more | On the rafter (standard installation) |
| Slate tiles | Less than 100mm | Between the rafters (recessed installation) |
Tip: Use our Rooflight Calculator Tool or contact our technical team for expert guidance when measuring and specifying your project.
Whether you select a standard (on the rafter) or recessed (between the rafters) installation, the goal is the same – achieving a balance between aesthetic finish, practical performance, and structural integrity.
Both approaches deliver exceptional results when installed correctly. For detailed advice or technical support, contact The Rooflight Co. team or explore our case studies to see these installation types in practice.
Send us your details and our team will be in touch.
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