Compact Roof

[amin]

I’m doing a loft conversion and adding a flat roof infill as part of that. Due to head height issues, I can’t go for a warm roof, and I want to avoid the issues of cold roof ventilation and PIR fitting between joists.

 

The Siga “compact roof” and Partel unventilated roof systems seem promising as space saving, insulation-between-and-over solutions. They also seem to avoid the need for ventilation and allow for continuous insulation. I’ve attached some images of the build up. 

 

Has anyone built this type of roof? If so a few questions for anyone with experience:

 

- What products have you used for the intermediate waterproofing layer shown in these types of diagrams?

- Are there any practical issues I should be aware of when building this type of roof?

- Is there a reason this roof type doesn’t seem to be commonly used?