Inverted Roof Insulation

Inverted roof insulation consists of rugged panels installed on top of waterproofing on inverted roofs. These boards withstand foot traffic and weather, repel water, and protect the waterproof membrane underneath, while also providing thermal insulation to the structure below.

What is an inverted roof insulation board?

Inverted roof insulation boards are insulation panels that go above the waterproof layer in a roof. They are specifically built to work with inverted roofs.

These roofs are constructed with the waterproofing layer positioned beneath the insulation. In typical flat roofs, the waterproofing layer is laid above the insulation.

Inverted flat roof insulation panels are manufactured using hardy materials, usually water-resistant XPS, since they will be protecting the waterproofing membrane and supporting foot traffic or landscaping layers.

Most boards also have a specified compressive strength – usually between 300–500 kPa – to ensure they can safely handle people walking on the roof.

What is inverted roof insulation used for?

Inverted insulation is ideal for walkable or usable roof spaces. It can be covered with gravel, decking, slabs, soil, or light paving and is common in spots like:

• Roof balconies and terraces
• Green roofs complete with soil and plants
• Roofs finished with gravel or ballast
• Walkable flat roofs on commercial buildings
• Service roofs where maintenance crews walk around

XPS boards are suitable for foot traffic and light landscaping loads in these spaces. Consult a structural engineer for higher load requirements.