Nodules on rubber roof; rubber roof longevity?

**Ernie Simpson** · 07-21-2011, 08:11 PM

Had a commercial inspection today. Building has a rubber (EPDM) roof. Installed over a solid metal roof integral to the 1940 trusses. I saw these hard nodules on the roof surface. Are they piece of the metal roof that have changed their chemical composition? Haven't seen this before. (Roof was older and had loose seams so I basically said it was at end of life, confirm with roofer and get cost estimates, etc. )

On a more general note: how long do you find EPDM roofs lasting. I have a tough one with this as these roofs don't show wear factors like an asphalt shingle roof will. I have very occasionally seen these roofs just fatigue and split - but this is very uncommon; plenty of bad installations too. But many rubber roofs look the same at 15 or 20 years that they did a 3 years. So, how long should these roofs last, even with good installations. I like to say 25 to 30 years, with one reseaming job over this life. Too much or too little?

Feedback?

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**Ernie Simpson** · 07-21-2011, 08:26 PM

Forget photos. Attached.

David Valley · 07-22-2011, 03:02 AM

Ernie,

Those circular defects appear to be melted areas from a hot object dropped on them. The open seams are obviously in need of an upgrade as you stated.

I tell my clients that EPDM roofs typically last 30 years.

If I were inspecting this particular roof I wouldn't report that the entire roof needs to be replaced, I'd simply recommend an EPDM specialist to repair or replace defective areas.

**Scott Patterson** · 07-22-2011, 06:29 AM

Depending on the weight(millage) EPDM membranes will have a factory estimated life span from 15 to 30 years. Firestone has some great information on their website, I use their literature for basic information when I have a question on EPDM. From what I understand Firestone has the majority of the EPDM market so they are a pretty safe source.

David R. Bonaparte · 07-22-2011, 07:21 AM

the nodules are difficult to determine cause...but as far as the edge metal...i dont see any evidence of an uncured roll application tying the aluminum gravel cleat to the edpm.
I also dont understand the two different dimensions of edge metal. Either way...this is an easy fix because at least it doesnt have to be done over...it just needs to be done for the first time.

David

**Joseph Ehrhardt** · 07-24-2011, 08:52 PM

I have done my share of flat roofs, not sure I understand the EPDM installed right on the steel roof, typically brown board/ insulation is screwed down to the corrugated steel deck, plank or Tectum . My question were those circles in a pattern which would be the fasteners corroding in a perfect circle?

**Garrett Merrick** · 07-26-2011, 05:02 AM

EPDM roofs that I have seen in hot and sunny Utah typically last the 30 years that you quoted. At 10-15 years the lap sealant begins to crack and would benefit from a re-application. Also about this time I have seen some (shouldn't be many) of the laps begin to lose their adhesion and start leaking. I like to verify that all the sheets are lapped uphill to the water flow (like asphalt shingles) to minimize the chance of standing water flowing into a defective lap adhesion; I've seen some that were not.

**Ernie Simpson** · 07-30-2011, 05:55 PM

Thanks all for the feedback. I think Joseph Ehrhardt's comment rang a bell on something: the metal nodules appeared to be centered, so they may indicate some type of metal fastener that is now protruding through the material (the roof needs repairs or, more likely, replacement, in any case). This roof appears to be installed over some type of metal roof with possibly a thin board sheathing over that).

**Matthew Steger** · 08-02-2011, 06:16 AM

Originally Posted by Ernie Simpson

Thanks all for the feedback. I think Joseph Ehrhardt's comment rang a bell on something: the metal nodules appeared to be centered, so they may indicate some type of metal fastener that is now protruding through the material (the roof needs repairs or, more likely, replacement, in any case). This roof appears to be installed over some type of metal roof with possibly a thin board sheathing over that).

As most EPDM roofs used in my area (PA) are typically either a 0.045" or 0.060" thick and this material typically wears at 0.001" to 0.0015" per year (per most EPDM manufacturers) I most often report that a 0.060" (most common around here) should last at least 35 years assuming regular maintenance. In most cases, the manufacture imprints something on the material stating its thickness like a "..45.." or "..60..". If I can't visually confirm thickness, then I state I can't tell.