An inverted roof places insulation above the waterproof covering. Protective or ballasting layers above the insulation may form part of the selected roof system.
What does this mean on your roof?
This sequence differs from a warm roof, where insulation sits beneath the waterproof covering. Material suitability and drainage detailing therefore matter.
Not every insulation board suits every position. The system description needs to explain more than the desired thickness or a generic thermal rating for an isolated product.
During maintenance, upper layers can affect access to the waterproof membrane. Ask how an outlet or junction remains accessible and how displaced material will be reinstated after investigation. Additional load and available height also need assessment. Keeping existing waterproofing still requires understanding its condition; new layers above it do not establish that the underlying roof is free from defects.
Frequently asked questions
Can any insulation go above the membrane?
No. Materials and the complete application must suit this arrangement.
Will inspection of the membrane remain simple?
That depends on upper layers and access. Include maintenance in the design.
Consulted 19 September 2026. Check requirements for your own address and selected system.