Tearing off a single layer of a two layer roof and roofing over the first layer? (Flat Roof)

We have a potential client who wants a commercial tear off and replace. It’s a small business (25sq). We went up to the roof the other day to take a core sample and found that there is currently two roofs on it, the first being a tar and gravel and the second and top layer is a torch down.

I want to provide an alternative option to the client in case they don’t like the price of a double tear off and install. A roof over is not an option because city code only allows two layers max.

My question is, is tearing off the top torch down layer only and roofing over the tar and gravel with polyiso board and TPO a viable alternative?

It should also be noted that I hate roof overs and would much rather go to the deck. But considering its a small business, and its not an insurance job I want a last resort if the property owner absolutely can not afford a full tear off. I am of course going to push for the full tear off first.

I’d need to know more.
Did they burn the torch directly on top of The spudded Rock?

When you walk across the roof,
Does it look smooth or is it real bumpy looking?

Thanks for your reply

I dont think the top layer is fused with the layer under it because when I took the sample I pulled up on it and it came right apart. Oddly enough though the roof looks pretty smooth all things considered. It’s just slightly squishy when you walk across it. Also I didn’t see any insulation in the core, just what looked like tar, rocks, and the top layer of torch down.

I assume its torch down because it has tar oozing out the lap seams. At first I thought it might of been sbs.

That’s the problem with laying over flat roofs. Nobody puts one on until they have leaks. Vapor vents are mandatory on a recover, but it’s rare to see them installed. The real question is how much rotten deck are you covering up?

You bring a very good point to the table. For the most part the deck is quite sturdy but there is a problem area in the back where water is pooling up, And likely this is rotten decking there. We were considering only tearing up that part fully and building it up with insulation.

That’s so true though, some people dont even call a roofer until it’s been leaking so long that their rafters are rotten, it baffles me.

steel deck/bar joists or wood /rafters?

I know the deck is wood, I can only assume the rafters are too because it’s so old

You won’t meet fastener pullout specs without solid deck.

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