Choosing a Flat Roof: Understanding the Terms and Types of Membranes
Choosing the right roofing system for a flat roof can seem complex, especially when terms like white roof, green roof, or inverted roof come up. These expressions refer to different types of flat roof configurations.
Meanwhile, words like elastomeric roof or TPO roof refer to the types of waterproofing membranes used to cover and protect these roofs.
In reality, every flat roof is covered with a specialized membrane — and it’s this membrane (elastomeric, TPO, EPDM, or built-up asphalt and gravel) that provides protection against the elements.
In this guide, we break down the most commonly used terms, their features, and their benefits — to help you make an informed decision based on your needs.
Types of waterproofing membranes for flat roofs
Asphalt and gravel roofing
Asphalt and gravel is not considered a membrane in the modern sense, but rather a multi-layer roofing system that was widely used for flat roofs — mainly before the emergence of newer membranes such as elastomeric, TPO, or EPDM.
Also known as hot bitumen roofing, this system consists of several layers of asphalt-saturated felt (bitumen paper) fused together with hot liquid asphalt applied at very high temperatures. The surface is then covered with gravel, which protects against UV rays and physical impact.
When properly installed, this type of roof offers good thermal performance and wear resistance, while remaining relatively affordable upfront. However, it also comes with several drawbacks: more complex and messy installation, higher maintenance needs (especially due to loose gravel that can shift or trap debris), and declining popularity in residential projects, where it is increasingly being replaced by more durable and easier-to-install modern membranes.
- Usage: Suitable for both residential and commercial buildings
- Composition: 5 layered system of asphalt, felt, and gravel
- Advantage: Proven solution with a good initial cost-to-performance ratio
- Drawback: Shorter lifespan compared to modern membranes (approx. 20 years)
- Maintenance: May require annual maintenance to retain performance
- Warranty: Standard manufacturer warranty of 10 years (may vary by installer)
Elastomeric roofing (SBS)
Primarily used in residential and commercial applications, the elastomeric membrane is a modified bitumen (SBS) system recognized as one of the most durable and robust options on the market. With a two-ply structure and resurfacing capability, it offers a lifespan of 25 to 30 years or more. Certified membranes from manufacturers like Soprema are high-quality solutions.
With an initial cost only about $2 per square foot higher than the cheapest option, its long-term durability and resurfacing potential make it a cost-effective investment. Additionally, its thermal properties contribute to better insulation, which can help reduce electricity consumption.
- Usage: Primarily residential and commercial
- Composition: Modified bitumen (SBS), two-ply system, resurfacing possible
- Advantage: Long-lasting, robust, improves thermal insulation, may reduce energy use
- Drawback: Higher initial cost (~$2/sq.ft more than the cheapest option, but more economical long term)
- Maintenance: Low maintenance required; resurfacing extends lifespan
- Warranty: High-quality certified membranes (e.g. Soprema), typically backed by solid manufacturer warranties
The EPDM membrane
Primarily used for commercial and industrial flat roofs, especially on very large surfaces, EPDM is a black synthetic rubber membrane known for its high durability (20 to 25 years). This proven waterproofing solution is popular due to its generally reasonable cost and eco-friendly profile.
Installation is considered complex and requires specialized expertise. In addition, its standard black color tends to absorb more heat than lighter membranes. However, as a single-ply system with few seams, it offers excellent flexibility and is highly effective for expansive roof areas. Manufacturer warranties typically range from 15 to 20 years (Firestone, Carlisle).
- Usage: Mainly for large commercial and industrial flat roofs
- Composition: Single-ply black synthetic rubber membrane (EPDM)
- Advantage: Durable (20–25 years), proven solution, few seams = high flexibility, good value, eco-friendly option
- Drawback: Complex installation requiring expertise, black color increases heat absorption
- Maintenance: Semi-annual inspections and cleaning, with attention to seams and drainage
- Warranty: Typically 15–20 years, offered by manufacturers like Firestone and Carlisle
The TPO membrane
Primarily used in commercial and institutional settings, TPO (Thermoplastic Polyolefin) is a white single-ply thermoplastic membrane. It offers a lifespan of 20 to 25 years, with 20-year warranties available from manufacturers such as GAF, Firestone, and Carlisle. This system is widely regarded as the most economical choice for large surface areas.
Its benefits include heat reduction due to its reflective white surface and fast installation. However, it’s important to note that TPO is considered more fragile compared to other membrane types.
- Usage: Mainly commercial and institutional
- Composition: White single-ply thermoplastic membrane (TPO – polyolefin)
- Advantage: Cost-effective for large areas, reduces heat (reflective surface), fast installation
- Drawback: More fragile than other membrane types
- Maintenance: Not extensive, but increased monitoring may be needed due to fragility
- Warranty: 20-year warranties offered by leading manufacturers such as GAF, Firestone, and Carlisle
Other terms used
White roof
White roofing is an increasingly popular solution for residential, commercial, and institutional buildings. It involves applying a light-colored coating or a reflective membrane, such as TPO or PVC, to reduce heat absorption through the roof.
This type of roofing helps lower air conditioning needs during summer and contributes to reducing urban heat islands. While highly effective in warm climates, its benefits are more limited in colder regions, where solar heat gain can be advantageous during winter months.
Sandwich roof
The sandwich roof is a pre-fabricated roofing system, particularly suitable for industrial, commercial, and agricultural buildings. It is composed of two metal facings, usually galvanized or pre-painted steel, which encapsulate a rigid insulating core such as polyisocyanurate (PIR) or mineral wool, depending on the required thermal resistance or fire rating. Thanks to its self-supporting structure, this type of panel provides both high thermal insulation, effective air and water tightness, and mechanical strength suitable for large spans and snow loads.
The inverted roof
Primarily used for flat roofs, both residential and commercial, the inverted roof stands out due to a reversal of the traditional layer order. The waterproofing membrane is placed directly on the roof structure, followed by the thermal insulation layer. This innovative system effectively protects the membrane from weather exposure, thermal shock, and mechanical damage, thereby enhancing durability and resistance to climatic stress. Insulation is often done using extruded polystyrene (XPS) panels for their moisture resistance.
The green roof or the vegetated roof
The green roof is a multi-layer system that incorporates vegetation (waterproofing membrane, drainage, substrate). It offers significant environmental benefits: reduction of stormwater runoff, improved thermal and acoustic insulation, support for urban biodiversity, and mitigation of urban heat islands. Despite a potentially higher initial cost, its durability can lead to long-term savings. Maintenance depends on the type of vegetation selected.
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Vous recevrez un devis détaillé et gratuit dans un délai de 24 à 48 heures suivant votre demande. Aucun dépôt n’est requis à la signature.
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La majorité de nos projets sont complétés en une seule journée, pour une superficie moyenne d’environ 1500 à 1700 pi². Vous êtes informé à chaque étape du processus.
Lorsque installée correctement, une membrane élastomère a une durée de vie moyenne de 25 à 35 ans. Grâce à la technologie de resurfaçage, il est possible de la renouveler jusqu’à 4 fois, sans tout arracher.
La membrane élastomère est la plus fiable sur le marché depuis plus de 40 ans. Elle offre durabilité, résistance aux hivers québécois et la possibilité de resurfaçage, ce que peu d’autres systèmes permettent.
Oui. Nous sommes certifiés RBQ, APCHQ, CAA, SOPREMA, IKO, et agréés Firestone. Nous sommes également membres du BSDQ pour les projets commerciaux.
Absolument. Nos toitures sont couvertes par une garantie de 10 ans sur la main-d’œuvre et 10 ans par le manufacturier. Nous nous engageons à assurer un travail de qualité et un suivi rigoureux.
Nous restons disponibles même après le chantier. En cas de souci ou de question, notre équipe vous répond rapidement, généralement en moins de 24 heures
Oui. Nos membranes resurfaçables sont une alternative durable et écologique, qui évitent de générer des déchets lors d’une réfection complète, tout en réduisant vos coûts à long terme.
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