Almost white as snow

The TPO membrane roof was completed this past week.  Overall, its a 100% improvement over the old roof, and I hope it will last until our daughter gets through college (with some maintenance).

I paid close attention to the install method out of curiosity, since it seems like there are at least 3 choices out there.
1.  'fully-adhered' - the TPO membrane is glued to the substrate
2. 'mechanically-fastened' - the membrane is fastened to the roof with circular metal plates with screws through them (like huge washer)
3. 'RhinoBond system' - relatively new idea where an electro-magentic induction 'welder' heats up the metal fastener plate *through* the membrane, and the membrane sticks to the plate with the aid of a weighted magnet to help the weld set (magnet top - TPO middle - hot fastener bottom).  The advantage of this is you can put the fasteners anywhere under the TPO, use less fasteners, and you don't need to create a hole in the membrane.

I thought I was getting the glued on membrane, since the roof board was listed in the contract, and any videos or diagrams of TPO roofing showed a three layer system of
- (1) insulation and (2) roof board mechanically fasted to deck
- (3) TPO membrane glued to roof board

After the main TPO membrane was installed (in one day), I went to check it out.  It looked really great, since it was so flat and clean, and the major seams were really solid. But, I noticed the roof was squishy.  I wondered if there was any roof board under the TPO.  It didn't smell right that one whole layer of the roof system was missing.  I called Lakefront Roofing supply, and they said the roof board was $16/sheet, so this would be a significant cost savings to the installer (at least $600 in materials alone).  Regardless of which of the three install methods were used, the roof board might be considered integral to the TPO roofing system.

Johns Manville TPO diagram

After some discussion with the installer, he said the roof board listing in the contract was a 'typo', and the RhinoBond system was used to adhere the membrane.  That's neither here nor there.  JM website states the roof board (otherwise known as 'cover board') is optional in their RhinoPlate solution guide (RS-8680).

new TPO roof! needs a couple rain showers to clean off the shoe marks

round dirt marking above fastener

'Surface mounted counter flashing' around chimney, and clay coping tiles on parapet wall

3 pitch pans with correct flashing (unlike my previous hack job)


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