Before you clean off an old flat roof...

[Sam Leon]

Well I think I kind of hit the jackpot...One month into a new rental purchase, I have to bite the bullet for a new roof, a subterranean termite treatment and a drywood termite fumigation.

Property has a flat roof, traditional 2 ply asphalt, with multiple patching over the years, I know the roof is near the end of it's life, and may even been living on borrowed time.

When we inspected the property there was just so much leaves on the roof, that it was holding up a "mat" of leaves sitting there for years and with the south florida rain and sun, those leaves have turned into compost.  Under the new leaves is an inch or two of composted organic matter, I am sure it's good for planting, because there were plants growing out of it.

After I closed, I had a company come by to clean the roof.  They used a giant push broom to push all this stuff off the edge of the roof.  The result is a pile of wet mushy debris about 9 cubic YARDS in volume!

When we used a garden hose to hose off the roof, the next day one tenant called and said the roof's leaking in one bedroom, and another tenant called said they have a leak by the kitchen...there was absolutely no evidence of leak, no stain whatsoever inside, and tenants both said there wasn't any leak since they moved in.  Not even during the rainy summers.

The only explanation I can think of, is this thick mat of disintegrated leaves and debris had been acting as the top layer of the roofing membrane, and once we cleaned it all off, the old roof below started to leak.  A week later we had some additional showers in the afternoon, and the leak continues.

As I got estimates for repairs and reroofs, I noticed termite droppings inside along some baseboards, and one tenant told me about occasionally spraying of "coffee ground" looking pellets in the closet shelves, so I started to get estimates from termite control companies for fumigation, while one company looked around inside and outside for evidence of drywood termites by observing kickout holes and pellets, he noticed one interior door was totally hollowed out...Poking a hole into it, a a few live moving subterrainean worker termites fell out, inside are some mud tubes.  Oh boy.  I need a full perimeter treatment below for the subs and a tenting up top.

This is one month into this purchase, and I am dealing with a new roof, two species of termites.  Fun fun fun.

Anyone redone a flat roof lately?  I am getting bids from roofing contractors and am debating between the traditional 2 ply asphalt (cap sheet, hot mod layers of modified felts or fiberglass), versus TPO, versus PVC, and also underneath them, a tapered insulation to give it a bit of pitch for water runoff.  Never seen a TPO or PVC roof, so I am not sure of their longevity and whether it is worth the extra $.

[Dave Hill]

As an experienced contractor, forget the 2 ply Built up Roof (BUR) that's a maintenance system at best.  Consider a torch applied APP modified bitumen instead.   To be code compliant the roof needs to be sloped a minimum of 1/4" per lf, with built in crickets to direct the rain water flow to the drainage locations, if required because of the roof configuration.

Now about tapering (building the slope) there are three basic methods:
1.  Carpenter approach, that is frame it and sheath it with plywood.

2.  Design a tapered insulation system using Expanded Poly Styrene EPS and use a recover type board over the top to separate the insulation from the torch applied membrane.

3.  Similar to 2 above, except using Poly Iso Cyanurate to gain a much higher R value, if that is an important consideration.  Poly Iso is available in stock panels to do this.

Roof venting is an important consideration, either into and out of an attic space or the joist cavities - you need both intake and exhaust.

Now about single ply roofs which come in various thicknesses, I'm considering 45mil products here which is the usual residential thickness sold - TPO is the cheapest but usually costs more than a torch applied APP.  PVC costs about 10% more in our market and the top of the line KEE (a modified PVC with woven and sealed reinforcement is 30% higher.  They all require high quality workmanship skills with TPO the most difficult to handle because of its stiffness.  Robotic welding is required on all seams exceeding 10lf by manufacture convention.  If the contractor doesn't have a robotic welder don't do business with them. 

More help is available in terms of advise if needed, just let me know.