Flat roof re-roof debate - Contractor Talk - Professional Construction and Remodeling Forum

bob_cntrctr · 09-09-2009, 08:25 PM

Gentlemen,

I'm not doing this one myself, outta my league - but I'd love your opinions on what's the best thing to have someone else do.

Dead flat roof on a century old Victorian. I haven't been up on it yet to know what it's currently covered with, but it's leaking - bad. Commercial guys will assure me that a properly done flat roof is bullet proof, stop whining. Call me a wuss, I figure gravity's about the most reliable thing on the planet. I want a slope.

EPDM on wedged insulation?

Standing seam steel on a new deck on wedged sleepers?

Or suck it up and torch or hot mop back onto the flat?

What is the apex of current technology for this?

Thanks.

Slyfox · 09-10-2009, 05:38 AM

The more slope there is the longer the system will last.

Metal properly installed on even low slope situations will last longer than any of the other systems you mentioned.

BTW, I'm a hot maggot, I have installed many a 4 ply dead asphalt, pitch and torch downs and you can easily get 20 years out of those systems with minor maintenance.
That don't change the fact the metal on a slope will last longer.

PA woodbutcher · 09-10-2009, 06:01 AM

duro-last roofing. I have seen it 20 years and hold standing water. I don't put it down, but have another contractor that does

Red Adobe · 09-10-2009, 08:25 AM

Im with sly pitch it and metal.

You can get many different styles besides standing seam or R.
With tax rebate and lower insurance there are alot of flat roofs getting pitched here

AaronB. · 09-12-2009, 09:56 PM

You could apply a seamless vapor barrier system unaffected by water like polyurea. On dead flat, if you went with metal, I would say you would havr to go with flat locked and soldered seams.

I still wouldn't put on a 4 ply asphalt with even a FR MB cap sheet cuz asphaltic products are all breathers.

Gilby · 09-13-2009, 05:26 PM

Duro-Last I been doing it for 5 years and never had a roof fail. I have seen it twenty years old just l like Wood Butcher said and it still don't leek. It dont have to have a slope.

Scott Siegal · 09-13-2009, 09:16 PM

This is an easy project, but could be tricky. Metal would be great, but you still need a pitch to it. Since its level now, the best you can hope for is 1/4" per foot (with tapered insulation). This, as previously stated, will require flat lock seams that are fully soldered. This can get quite expensive and also requires maintenance (painting) if its not done in copper.

Durolast, a PVC product, would do fine but is more expensive than other PVC membranes as they custom make the roof and flashings. They also include the warranty fee in the cost of the material, which may not be necessary since this is residential. (Durolast does not give full warranties on small residential properties as so many other manufacturers of flat roofing products).

I believe that PVC would be the best product in this case. My choice would be IB roof systems as they provide a lifetime warranty for residential roofing properties. My second choice would be fibertite. Fibertite does not offer the same warranty, but their product is one of the more superior PVC products on the market as they use Elvaloy in the formulation.

You can research both of these products on their websites. In the end, IB would be the best option (in my opinion). By the way, I have been installing flat roofing systems for over 20 years on residential properties in the Washington DC area.

Good luck. If I can answer any questions or be of any help, I would be happy to do so. I am new to this forum.

bob_cntrctr · 09-14-2009, 09:01 AM

Appreciate all the answers so far - just so everyone knows I'm still reading. I'll be researching the various membrane systems mentioned.

As for pitch and tapered insulation - I think I'd be more likely to tear off the old deck (most likely 1" x 12" barn board) and frame a 1/4" to 1/2" pitch to it, building onto the existing - at which point I could either way, membrane of metal.

dennis · 09-14-2009, 09:28 PM

Quote:

What is the apex of current technology for this?

A flat lock soldered seam copper roof.

AaronB. · 09-14-2009, 11:13 PM

80 mil seamless polyurea. Simple.

theflynner · 09-21-2009, 11:58 PM

Tear-off all roofing materials to wood deck, and install 1/4" tapered Polyisocyanurate insulation. Fasten to deck with 5 screws and plates per 4' x4' board.

Adher and 60-mil EPDM Rubber or 60-Mill PVC, (TPO?) to insulation with bonding adhesive. Use new lumber at details, and properly flash all edges. The workmanship of the perimeter will determine the quality of the roof. Hold back your final 20% payment untill a few thunderstorms have tested the roof.

Grumpy · 09-22-2009, 07:12 AM

Slope it no less than 1/8" per foot, preferrably 1/4", with tapered insulation. Your choice of membrane. I prefer white theromplastic single ply such as TPO or PVC.

Metal is fine if it's flat locked at the low slope. It it's steep sloped (3/12+) then standing seam willbe ok. I'd be afraid to do standing seam less than 3/12. Metal will most likely cost signifigantly more than a low slope membrane.