Rolled asphalt roofing is the cause of your problems, and if it started leaking – it cannot be fixed. This product does not last mor than 5-7 years.

I recommend doing either IB PVC roof and floating deck or IB Deck Shield, wich is also a PVC membrane, but can be walked over, and will be less expensive in the end, as you do not need to build a deck on top.

You will also need to consider drainage issues, to get water off those roofs.

Where are you located? I can help put you in contact with certified IB Roof Contractors, or if you are in New England, we can help you out.

Best of luck.

What you are referring to is “Green Roof”. PVC roofing is perfect material for that – I do recommend going with thicker 80-mil membrane and using modular green roof such as Green Roof Blocks (http://www.greenroofblocks.com).

You can then grow Green Roof plants / grass which can grow in as little as 4″ of specially designed for low weight soil.

This is an expensive “garden” though – so do your research first.

Good lick.

You can find some approximate pricing here: http://www.coolflatroof.com/roof-deck.php

Just use pieces of rubber mats to separate the rafters from roof.

I recommend you thoroughly inspect the roof before building the deck – if it leaks – it will be big mess taking the deck apart to fix a leak.

Better yet, install a low-slope system like PVC, before building a deck. I know this may not be realistic (budget-wise), bit it will be cheaper than building a deck, taking it apart to fix leaks and then putting it back together.

If you still plan to build it on current roof, put in your contract that you are not responsible for future leaks, say after first 3 months of you installing the deck (if it leaks in the first 3 months – it is probably you puncturing the roof).

Also build deck in sections, if you suspect it may leak soon – it will be easier for you to take it apart later.

Good luck