Three materials, two approaches
Elastomeric is a two-layer system of modified bitumen. TPO and EPDM are single-ply membranes, where one thin sheet does all the waterproofing.
Elastomeric
An elastomeric membrane is thick, granulated and torched in narrow strips.
- Strengths. Elastomeric resists punctures and foot traffic, shapes around the many details of a small roof and can be repaired in patches. Roofers in the region know it very well.
- Limits. The system has many seams, installation takes longer, the torch is common and the weight is higher.
- Lifespan. An elastomeric membrane lasts roughly 25 to 35 years, depending on the manufacturer and the quality of installation.
TPO
TPO is a flexible plastic sheet, most often white. The seams are welded with hot air, without a flame.
- Strengths. The smooth white surface of TPO is highly reflective. Wide sheets leave few seams, the system is light and installation involves no open flame.
- Limits. A TPO sheet is thin and more sensitive to sharp objects and debris.
- Lifespan. A TPO membrane lasts roughly 20 to 30 years, depending on the manufacturer and the quality of installation.
EPDM
EPDM is a synthetic rubber delivered in very large sheets. It is most often black.
- Strengths. EPDM stays very flexible, even in deep cold. It is light and leaves few seams on a simple roof.
- Limits. EPDM seams are glued or joined with tape, not melted. These seams are the point to watch over the years. The usual dark colour of EPDM can be a problem where a reflective roof is required.
- Lifespan. An EPDM membrane lasts roughly 20 to 30 years, depending on the manufacturer and the quality of installation.
What matters on a plex roof
A duplex or triplex roof is not a warehouse roof. It is small and crowded with obstacles, with parapets on four sides, a chimney, vents, skylights and sometimes a deck.
On this kind of roof, the advantage of wide sheets disappears. The membrane must be cut everywhere, and every cut is a detail to get right. Elastomeric is at ease on a small roof crowded with obstacles.
On an open roof, such as a garage, an extension or a building without obstacles, the math changes. A well installed single-ply membrane does excellent work there.
The white roof requirement
When a roof is replaced, most boroughs require a reflective roofing. White TPO meets this requirement by nature. Elastomeric meets it with a white-granule cap sheet, depending on the product. For EPDM, look closely at the version proposed.
Frequently asked questions
Which membrane lasts the longest?
On paper, elastomeric has a slight edge, at roughly 25 to 35 years against 20 to 30 years for TPO and EPDM. In practice, installation, drainage and maintenance make more difference than the material.
Is TPO cheaper than elastomeric?
The price gap between TPO and elastomeric depends on the roof. Only quotes for your roof can answer.
Can I put back a black EPDM membrane when the roof is replaced?
If your borough requires a reflective roof, a black membrane may not be accepted. Check the rule with the borough before choosing.