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Jkotowski 06-30-2013 08:06 PM

Flat roof - do i need to tear down the old?
I'm looking to re-do my flat roof in a semi detached home in Toronto; one of the contractors said that I can put it on top of the existing one (it looks like it has 2 roof already). This would save me 50% on price.

Any advise on whether it's worth tearing down the current one?


AndyWRS 06-30-2013 10:11 PM

That is dependant on if it is one or two layers atm. You can't go over two existing layers. You should tear off all existing layers.

Windows on Wash 06-30-2013 10:40 PM

What are the two previous layers?


What is he proposing in terms of the new roof?

PatChap 07-01-2013 08:06 AM

Going by Toronto, is he proposing to just torch a new cap sheet down over the existing, without any sort of recovery board or anything? I see this a lot.

Jkotowski 07-01-2013 12:31 PM

I am not sure how the existing roof has been laid down.

He said he would two two layers with torch down.

My two concerns are added weight to the roof and durability of the new roof - hence looking for advice.


jagans 07-01-2013 02:51 PM

Tear it off down to the structural deck. This gives you a chance to look at and repair any problems in the deck. You generally do not want to attach a new roof to a failed existing roof. There are exceptions, but it does not sound like you have one of them.

I would personally never use a torch applied product on a wood framed home. as it is very possible to burn down your home.

If you are working with a real roofer he will have a kettle to heat asphalt, and he can install an SBS mopped down Mod bit over a glass base sheet or you can have them use cold process adhesive. Always apply Mod bit in two plies.

You can also use a real single ply like EPDM, or PVC.

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