# thoughts on TPO coated metal?



## Grumpy (Oct 29, 2008)

We've used the TPO coated metal a few times. However I am a fan of redundancy. I like to wrap my roof membrane over the edge of the wall, then install my metal atop the membrane, then strip in the metal with other cover tape or more membrane. I feel that this strip in adds the layer of redundancy and when it does fail, worst case the water rolls under the edge metal/gravel stop/gutter flash. 

However with tpo coated metal, if I understand the detailsa bd specifications properly (and I am going to do some more research actually once my wife's study group leaves and I can have my office back) the detail is to first install the metal, run the membrane up to the metal and weld it. A huge savings on time, but is it better?

In another thread I posted about an 85 square job, we've done two almost exactly the same. We did as ai described ran our roof a few inches over the edge, installed metal and stripped in. However it costs 7 rolls of cover tape just for the perimiters and I am thinking we can save a bunch by using the TPO coated metal, but I do not want to try it at a cost of quality.


So I want your guys opinions. How long will the bond of the tpo membrane to tpo coated metal at the edge really last?


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## Pie in the Sky (Dec 21, 2011)

Best detail IMO is to install a strip of membrane over the edge and under the metal which extends onto the roof 2-3 inches past the metal flange on the roof, Then you can heat weld the strip to the above membrane then the Metal. Make sense? Now your membrane is continuous to the edge but you have the redundancy of the extra membrane. It’s an EPDM detail really but I have seen roofers adapt it to thermoplastic roofs. I know it’s a heat welded seam but your already looking for redundancy so you are admitting it would fail. Why install a seam? you obviously have to get it approved by the manufacturer for warranty work.


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## 1985gt (Dec 21, 2010)

I'm same as you grumpy. One could also do a normal detail (membrane over the edge then metal) Then you could use reinforced 6" slit roll to strip it in. I think it would be a pain in the rear keeping the roll straight plus it would take more time double seaming. It would probably be about same money wise ofseting the cost of the cover tape with the labor and material. I just learned of a product that GAF has not sure if others do but its almost the same thing as the RUSS?RTS strip or what ever you want to call it. Has a tape on one side and you weld the other. 

Our thing is, that damn TPO metal is expensive.


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## Grumpy (Oct 29, 2008)

Pie in the Sky said:


> Best detail IMO is to install a strip of membrane over the edge and under the metal which extends onto the roof 2-3 inches past the metal flange on the roof, Then you can heat weld the strip to the above membrane then the Metal. Make sense? Now your membrane is continuous to the edge but you have the redundancy of the extra membrane. It’s an EPDM detail really but I have seen roofers adapt it to thermoplastic roofs. I know it’s a heat welded seam but your already looking for redundancy so you are admitting it would fail. Why install a seam? you obviously have to get it approved by the manufacturer for warranty work.


We do what you described with modified. Never seen it done by anyone but us though to be honest. 

Hmmm on a thermoplastic roof, that'd all have to be hand welded. 

I always assume a roof is manufacturer warranted when I spec it, and I spec nearly all of our jobs currently (very few are bid to spec by consultant or architect or what ever). On the jobs that are not warranted by manufacturer are guaranteed by us so we still worry about failures. Not to mention just plain doing what's better rather than what's faster and easier. On the jobs when it is not manufacturer warranted, I may adapt a detail from another manufacturer which for what ever reason I prefer. I'm always looking for ways to save money, like anyone, but I don't want to do it at the cost of quality which will always come back to bit you in the ass. 


On this particular job I decided to stay with our original spec because that's what we did on the other buildings gravel stop and because this isn't gravel stop but is gutter flashing on this 3rd building. I worry about K style gutters on flat roofs and want a membrane behind the gutter.


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## RoofYourWorld (Jul 27, 2011)

It is tough to beat an EPDM edge with a cover strip. However, you can install several versions of a TPO edge with cover strip that work great.

This is just a quick screen shot I pulled from Carlisle's site that does a good job illustrating a detail I prefer. You get the membrane wrapped over the edge, your metal face fastened and top fastened, and a cover strip (welded) to encapsulate everything. 

Lots of contractors will use a white 'peel and stick' instead of heat welding the cover strip. In some cases this will work but you can expect it to start failing in places (UV damage) about 8-10 years in.


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## Grumpy (Oct 29, 2008)

Yeah other than the double edge metal with the clip, which I don't see the point of, that's how I prefer as well.


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