Roof deck over living space - what materials to use?

We have a 550 sq ft roof deck over a living space which must be redone this summer. But after 4 bids (and waiting for 2 more) we are unsure of what materials/contractor to go with.
One planned to do TPO, another mentioned Metacrylics, another Graco deck coating (not Gaco, although can’t find any info on Graco), another does only cementitious Poly Tuff waterproof deck coating, and the last planned on modified bitumen. The bids range from all over the place from around $4000 with TPO/metacrylics to $9000+ for poly tuff.

TPO is slippery and I doubt it’s ability to hold up to foot traffic, and I’ve read that liquid membranes (metacrylic and Graco) fail quickly and need regular maintenance. Aesthetically poly tuff wins out, but is so expensive and would require a framer to come out and redo the pitch at an added cost. Modified bitumen seems slightly more sturdy than TPO, but I again question it’s ability to hold up as a deck as well as a roof.

We’re oddly both overwhelmed and disappointed with our options so far, so any input on the materials mentioned above or on anything else out there would be greatly appreciated!

I assume this is a walking deck, no? Mod Bit and TPO are not suited for a walking deck. Graco is the name of a paint sprayer, not a roofing system. They mean GacoDeck. #1 concern is that you have a suitable plywood substrate. Plywood should be 1.25" T&G if you want the deck to hold up to foot traffic. If the deck is solid, you can use any number of pedestrian systems. ITW Polymer Sealants, Tremco and others make good elastomeric systems. They will take some movement in the deck. Typical reasonable warranties are 5 years, but that really is only because of wear not failure of the coating.

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I realize that this thread is more than a few months old. Nonetheless, I’ve revived it because we are facing precisely the same problem. Our situation is almost exactly the same, right down to the 550 square foot deck size. We too have gathered multiple proposals, one for TPO, one for PVC, one for modified bitumen, and one for DeckShield (which I gather is a very expensive PVC variant). The only possible difference I can see is that all our proposals recommend installation over IsoGard. Unfortunately, I have my doubts regarding even that.

I spoke with Firestone regarding IsoGard today. The technical rep feels that IsoGard might well work; although, Firestone, of course, will not officially endorse such usage. Several roofers on this and other forums strongly believe that IsoGard is inappropriate for such an environment. There is similar disagreement regarding TPO, PVC, and modified bitumen. A small dissenting minority is one thing; but, on these topics there truly is widespread disagreement. Spending six to sixteen thousand dollars when half the experts contacted disagree with every solution takes some real chutzpah.

I suspect that much of this is due to the harsh demands of walking decks, especially those located over true living space. The care taken when using the deck probably varies greatly from one instance to another. There is probably a much greater chance of consumer dissatisfaction due to the active environment created on walking decks with conventional roof expectations regarding leaks in the living space below.

Forget TPO, roofing PVC,Mod Bit. They are roofing membranes, not walking decks. If you want a sheet membrane for the walking deck consider Duradek (the oldest), Tufdek and DecTec. These are all PVC membranes designed for walking decks. For the most part, I think they are all made by a firm in Canada. The other alternative is to use a liquid pedestrian coating such as Pacific Polymers or equal. IsoGard is great for a roof application but adds little to a walking deck situation. if you are looking for something to put over the plywood to stiffen it up, consider Dens Deck Prime or SecureShield products. You really don’t need an underlayment if you have reasonable plywood decking. As I said before, it is good to have 1-1/8 t&g plywood or at least 3/4or 5/8 t&g.

@donl Mod Bit is not really a membrane :slight_smile:

@Laura I agree with Don, forget about TPO - it’s made for large open flat roofs - not for decks.

We use IB DeckSheild - its a heat welded system MADE FOR DECKS and to be walked on, even when wet.

More is here

Compared with rubber + wood deck you save about 40-45% and have a beautiful, long lasting and EASY TO REPAIR (if ever needed) roof deck. Easy to repair becuase you don’t have to remove wood or pavers, and have access to everything.

Also, the very important post and corner flashings are pre-fabricated and weld in place … like I did here:

Im installing a walkout from basement enclosed 14×18 ft room. On the top of the room is another walkout from my kitchen that will have a deck installed above the lower room. It to will be 14×18 ft. Could i use this IB Decksheild on just the lower rooms roof?
Any help would be much appreciated.

That would be one of the best products to use for a walking deck.

I wasnt planning on making that product my upper deck to walk on. I was thinking of melting the product around my post that would protrude up through the lower rooms roof. On the room below I would have a metal roof that has a 1/8 in drop per foot to one side to catch all the rain from above in a guttering system…
Any thoughts on that?

There is a specific way to flash posts.

If you aren’t going to be walking on it you can use something less expensive

Easier to flash brackets, then mount the posts

I haven’t seen many pictyres or any plans of people havibg a room addition on the walkout basement with a deck walk out above it. Would be nice if anyone has some insight .
Thanks to all who have responded

Does your droom below have footings for its foundation or is it just on a slab?
Im needing some advice.
Thanks