Inverted Roof


The longer-lasting roofing solution

An inverted roof (also known sometimes as a protected membrane or PMR roof) uses the same materials as a conventional roof but places insulation on the top of the membrane. Invented by Dow in the late 1960’s, an inverted roof system uses DuPont™ Styrofoam™  Brand XPS Insulation to protect the membrane helping improve the performance and longevity of the entire roof system.

Inverted roofs are becoming a popular alternative to conventional roofs because their benefits include long-term cost savings, sustainability benefits, and increased community resilience.

An inverted system works because DuPont XPS insulation is inherently resistant to moisture and durable enough to withstand exposure to the environment. DuPont XPS Insulation enables inverted roofs because it:

  • Resists water absorption
  • Provides excellent thermal performance
  • Is unaffected by freeze/thaw cycles
  • Withstands surface traffic
  • Provides long-term protection to the waterproof layer
  • Can be ballasted to prevent flotation
  • Protects roof layers from UV and mechanical damage

Inverted roofs are typically assembeled as vegetative, ballasted or plaza roofs. Explore each roof assembly in greater detail below or dig into the downloadable materials to learn more.


Ballast Roof

Ballast roofs are your typical inverted roof but using gravel to hold the roofing components into place. It’s an enconomic method for extracting the long-term performance and cost savings from the inverted roof design with anticipated lower upfront material costs.

Ballast roofs are also a suitable alternative to vegetative or garden roofs where rainwater collection methods for managing sewer system overflow during heavy rans can be employed. This design is approved for no slope.


Green Roof

A green roof, also called a garden roof, preserves the natural environment by simply placing it on a roof, known for a variety of benefits including preserving the local habitat, to reducing the impact of storm-water overflow.

There are two types of green roofs:

  • the green roof (extensive cultivation) with a substrate of the order of 6 to 10 cm and suitable plants.
  • roof garden (semi-intensive or intensive) with a minimum of 30 cm of topsoil

In both cases, it’s important to choose efficient and durable insulation such as Styrofoam™ Brand Insulation with high quality membrane and sealing protection.



Plaza decks and ranges of rooftop terraces are ideal for enabling unique, simple and economical opportunities to extend the utilization of the rooftop real estate.

Just like the Louvre Museum rooftop terrace – boasting DuPont's  Styrofoam™ Brand Insulation under sealed pavers – you can give your guests and occupants easy rooftop access to urban outdoor living.

Our Styrofoam™ Brand Insulation solutions are particularly suitable for accessible roof terraces. It protects the waterproofing against mechanical damage, both during work and during the use and maintenance of the roof.