# Most cost efficient product for a flat roof?



## LeRayParateur (Aug 23, 2018)

Hello all,

I would like your thoughts about a few different roofing options that have been offered to me.

This is for a small income property with a flat roof, in a climate where weather goes from -15F in winter to 90F in summer.

The actual roofing looks like patches over other patches so I don't trust it at all. Naturally, as it's an investment property I don't care how it looks as long as it's cheap and easy to maintain over the life of the property.

In my area, the roofers who have been around for a long time swear by Elastomeric Membrane (maybe because they are mainly tooled for this product and their staff knows it well), while some smaller firms offer TPO.

Overall, we can summarize the local offering to 3 options :

- Install elastomeric membrane over whatever's already there and double the attic ventilation rate (5 to 10 years warranty given by the installer, cheapest option)
- Strip everything to the wood decking, install elastomeric membrane and do nothing about the ventilation (most expensive)
- Cover everything with EverGuard TPO, single-ply roofing system, keep ventilation the same (20 years warranty backed by GAF, intermediate cost)

The best product might not even be listed in these options but I have to work with what the local guys can install.

I like that the TPO joints are welded instead of glued, and the light color prevents the attic and roof to become too hot in summer. 

The increased ventilation option is likely required to both evacuate moisture which would eventually rot the wooden deck and reduce roof temperature to prevent premature aging of the elastomeric membrane, but this might increase heating costs during winter, or even cause unforeseen moisture control problems in very cold weather if the vapor barrier isn't perfect on the warm side.

So far, I'm inclined to try TPO as if we spread the cost over the warranty period, it's about 30¢/sq ft-year with potential benefit of reduced air conditioning costs and no risk of unexpected consequences of the different ventilation rates.

I still worry that either this product is too new to know the long term performance, or that a potential buyer of the building will not trust it and prefer what everyone else uses.

Please also note that this is for a 90 years old building where I'm running my business and also have rental income. I'm not trying to make it perfect and might not hold it for life, just want the best return on my investment while avoiding cheaping out and creating maintenance headaches down the line or harm the resale value too much.

I guess there are horror stories for both products and am sure the skill and care level of the installer makes a big difference no matter the product.


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## Nlightleadfarmer (Sep 12, 2018)

Tapered insulation with tpo


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## LeRayParateur (Aug 23, 2018)

I finally chose to go with TPO.

The white membrane looks much brighter than the surrounding buildings especially on sunny days.

I think for best results, the skill and care of the installer is very important. Laying the roof seemed quick and easy, but welding good joints, meeting vertical surfaces, drip edges and flashing required a good attention to detail.

So far I'm glad I picked this product and this roofer's team.

Ray
Reparateur Electromenagers


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## atlroofman (Nov 23, 2018)

You chose the correct system. The other ways of doing it you describe were vastly inferior.

My company has been installing all types flat roofs consistently for 30 years.


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