In an inverted membrane system, the conventional membrane arrangement is inverted or turned upside down. Inverted roof membrane assembly (IRMA) systems are used in applications where the membrane requires protection from site-specific hazards. These systems are typically applied in conditions where there is extensive roof traffic or to protect from excessive weather conditions such as multiple hail events. IRMA roofs protect the membrane from ultraviolet degradation and constant temperature changes.
Proper IRMA design is as follows:
* The membrane is applied directly to the substrate. The membrane should be fully adhered to the substrate.
* Insulation is applied over the membrane in accordance with the manufacturer's requirements.
* Surfacing is applied over the insulation. Surfacing can consist of pavers, ballast, concrete pours, or vegetation with soil.
* Drainage can be accomplished with proper substrate slope (a minimum of 1/4 inch per foot) and substrate level drains, surface drains, filter fabrics or a drainage bed, depending on specific project requirements.