Roofing Membranes (EPDM vs. Hot Rubber) 1

[Cleigh]

I am inquiring to see if anyone has a long term experince with EPDM roofing & a Hot applied roofing. My research has shown that EPDM life expectency is 12-15 year, while Hot rubber is 15-20. Can anyone shed some light on this topic?

 

[Ron]

Cleigh...your info is correct. EPDM membranes have limited life spans without extraordinary maintenance. Yes, they are sold as "20-year" systems, but in reality I have not seen many of them make it to 15 years and I've seen many of them fail in less than 10 years. Most of the problems are associated with seam problems and shrinkage of the membrane pulling flashings loose.

Conversely, hot applied built-up roof systems are still the best systems available. Hybrid systems using a combination of conventional built-up roofing and modified bitumen cap sheet are, in my opinion, the most "bullet-proof" roof systems available.

Yes, there are some pretty good synthetic membranes on the market (EPDM is not one!), but they require specific repair techniques, careful application, and maintenance. A good built-up roof system will last for many years with minimal maintenance (note...minimal does not mean "no maintenance"...all systems require maintenance). Add that to the fact that if you have a roof leak on Saturday, you can usually pick up materials to fix it at the local hardware store without screwing up the membrane in the process!! I have provided inspection, consulting, and management of over 10 million square feet of roofing and built-up still comes out on top (sorry about the pun!).

Ron
ps...the term is hot asphalt, not hot rubber, though there are "rubberized asphalts" available (modified bitumens).

 

[RDK]

I agree with Ron a modified bituminous roof is still the best type to use. I also have a lot of bad experience with EDPM membranes, especially from a maintenance perspective. A traditional hot process roof can become brittle and cracked with age resulting in leaking due to freeze thaw effects. I have seen some BUR’s (built up roofs) over 40 years old.

Here in Canada with our extreme climate I like to use a mod-bit roof assembly in an IRMA configuration. (Inverted Roof Membrane Assembly). In this type of roof the membrane is protected by the insulation which is held in place by a ballast. The ballast, typical rocks or paving stones does add top the weight for the structure to support but the roof membrane is protected from the elements and from any roof traffic. Dow made a product called Roofmate CT which was a polystyrene rigid insulation with concrete bonded to the top which works well but drainage is an issue as ponding can lift the panels so that the tongue and groves do not fit back in place.

As an added benefit the vapor diffusion barrier is nearer to the warm side of the building envelop. In swimming pools and other high humidity areas you have to place some insulation under the membrane as well.
Rick Kitson MBA P.Eng

Construction Project Management
From conception to completion

http://www.kitsonengineering.com

 

[Cleigh]

Thanks Ron & RDK, I agree that the hot asphalt roof is better and will pay for its self many time over in the future. Do you have any suggestion on manufactures. We have been using Tremco (TP-150) & Hydrotect system (a natural rubber).

 

[Ron]

Cleigh...I don't want to get into bashing manufacturers but Tremco is bit on the expensive side with, in my opinion, no significant gain.

Johns-Manville, Siplast, Tamko, and a few others produce good, quality materials and offer good backup of their products. I would stick with domestic asphalt and use a 3-ply glass fiber felt system plus a modified bitumen cap sheet, all fully hot mopped.

Remember... in roofing, the devil's in the details!