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mymrbig 02-19-2013 08:08 PM

Flat Roof - probably not DIY for me
I live in southern Louisiana and part of my home has a flat roof that has a pretty terrible puddling problem. I have a fairly unimaginative roofer who my in-laws have used numerous times for years and he seems to keep wanting to just re-seal the flat roof every few years and never provides me with any suggestions on how to give the roof a little pitch to allow it to drain.

Common sense tells me that there should be some way to build up the center of the flat roof to allow it to drain to the edges, but I have no idea how to go about doing so. The roofer hasn't really offered up any suggestions other than continuing to re-seal. I recently noticed a few spots that are very soft and have me worried about leaks.

Is there something than would be an easy/cheap DIY fix? Should I let the old family roofer continue to just re-seal every couple years and ignore the puddle that lasts for days and days when it rains? Or do I need to find a new roofer who might have a non-DIY solution?

My skill level and time availability for a DIY project are pretty limited, but I'm not totally worthless. My roofer's 2 suggestions were: (1) add a layer of roll roofing above the current material for extra protection; or (2) do the same thing with something like a couple sheets of plywood between the current flat roof material (asphalt of some sort) and the roll roof, right where the flat roof puddles, to help it drain.

Thoughts? Many thanks!

mymrbig 02-19-2013 09:11 PM

A few more details, the puddle that forms is probably 10-15 feet long and eliptical, about 6 feet across at the widest. It has been forming since I bought the house 8 years ago and the flat roof has been re-sealed 3 times since we bought the house. My concern ratcheted up recently when we began noticing a slightly musty smell in corner of our dining room (where the pitched roof meets the flat roof). I went into the attic under the pitched roof and couldn't smell or see anything, though the area where the pitched roof meets the flat roof is covered by open-cell foam insulation. Of course, there is a wet wall in that corner of the room as well, so the musty smell might not be related to the flat roof (but I still want a good solution for the flat roof).

jagans 02-19-2013 09:39 PM

Have a real commercial roofer come in.

1. Tear off the existing roof to the deck.
2. Replace any bad decking you find in kind.
3. Install two stacked 2x6 nailers around the perimeter.
4. Install 1.5 inch Black Faced Isocyanurate insulation over roof.
5. Install a 3 inch commercial cast iron roof drain in the middle of the roof right in the lowest spot on the roof. Use sump receiver, cast iron drain body and CI dome. Don't get talked into plastic dome. demand stainless hardware.
6. Install 4 x 4 Tapered edge strip around drain.
7. Install .060 fully adhered EPDM roof. Strip in seams with 6 inch Pressure sensitive flashing. Install raised gravel stops of .040 aluminum, color match to home. Skirt must cover down over siding 2 inches minimum.
8. Coat roof with 2 coats of white acrylic every 10 years.

You will never need another roof.

hotrod351 02-21-2013 09:31 AM

depending on how large the area is thats holding water there is a product called emulsion, its like a thick pudding that i have used with success. if to large then agree = reframe with a slope or at least clean off then apply 4 coats of roof paint, might even need the webbing with the paint. but yeah the best thing is to get rid of the pounding. that will solve 95% of the problem.

1985gt 02-21-2013 11:40 AM

same as jagens or

Tear off

Remove 6 courses of shingles on sloped roof.

Install 1 layer 2x4 or 2x6 at roof edges you wish the water to drain off of.

Install 2 layers of 2x4 or 2x6 on other edges.

Install 1 1.5 base layer of ISo

Install 1/4 per foot tapered insulation sloping towards the roof edges you wish the water to drain to.

Install EPDM and assorted details.

EPDM to go up atleast 1' of the sloped roof, UNDER the felt. Re shingle to 6-8" of the flat roof.

Trim with metal, 24 ga steel, and new gutter on the sides it drains to.

Sounds like a very simple thing to do, get a real roofer in there. Added anymore to the roof may cause further problems. It's "sagging" now that is why it's ponding. if the 1/4" per foot taper wouldn't be enough to eliminate the pond, then you can use 1/2" per foot.

mymrbig 02-21-2013 11:58 AM

Doubt this changes anyone's suggestions, but the roofer told me that the current roofing material where the ponding is occuring is torch down. He said that despite the ponding, he thinks the roof is in good shape since we've been getting it re-sealed (or whatever the proper term is) every couple years. Rather than tear off the current roof, he wants to lay down some plywood across the area that is ponding to create a slope toward the edges of the roof, then just use roll roofing over that. We have a connected flat roof with roll roofing that drains well and has held up very well, so he is focussed on fixing the drainage problem at a reasonable cost, rather than re-doing the roof (because he doesn't think there is any damage underneath the torch down).

1985gt 02-21-2013 01:26 PM

IMO adding plywood on top of an existing roof is not "fixing" anything. And judging by what has been said the roof has very little slope at all, so adding plywood in this area may cause problems in other areas. Plus I would not put "roll roofing" on it. You would be better off leaving it alone. Unless he is defining roll roofing, since 90% of of low slope roofing products are on rolls.

Now this "resealing" Is this an aluma coating (shiny silver) most any coatings on top of the roof systems do little to seal them, it's a protective coating to keep the sun from breaking down the materials. The coating products do not do very well in ponding areas, and that is evident by the fact you have had to do it ever couple of years. Most coatings should last in the 5-10 year range on a decently sloped roof.

Again there is a reason why the roof is sagging in that area, it could be the home has settled, the insulation under the roof has been exposed to moisture and has compressed, could be people have preformed repairs in other area's that is backing up and making this a pond.

If you can put some pictures on here, it will give us a much better idea of what your dealing with. It will be much more helpful, maybe even the dimensions of the roof.

OldNBroken 02-21-2013 03:20 PM

Just based on the few things he has suggested tells us he has no clue what he is doing.

Do not even consider ANY of those things he has suggested. Those are the worst things you could do. (sorry for the caps, had to make sure you read it)

1985gt has given you the best solution, except I always recommend 18-24" up the slope. Gutter the new eave and you will be all set. An eps taper system is considerably easier and cheaper than all that new plumbing.
It sounds like at this point it is critical that everything be removed and start from there. Adding anything to the existing is only adding more weight to an already overloaded structure and exacerbating the problem.

And what the hell is roof paint for?

jagans 02-21-2013 09:08 PM

1. No Modified Bitumen does well in ponded water.
2. Low slope roofs fail where dissimilar materials move differently under thermal load. IE where metal ties into bituminous or elastomeric material.
Getting the metal edge out of the water line, and installing an internal roof drain eliminates this.

3. Adding slope is good.

1985gt 02-22-2013 12:20 PM


Originally Posted by jagans (Post 1122082)
1. No Modified Bitumen does well in ponded water.
2. Low slope roofs fail where dissimilar materials move differently under thermal load. IE where metal ties into bituminous or elastomeric material.
Getting the metal edge out of the water line, and installing an internal roof drain eliminates this.

3. Adding slope is good.

1. So do single ply's, the point is to get the ponding water off the home.
2. Gutters, drip edge and the associated materials are a heck of a lot cheaper then a 200+ dollar drain tearing out a ceiling and a plumber. Drains have their own set of problems, and putting one in a home some times doesn't always work.
3. Very good!

mymrbig 02-26-2013 10:56 AM

1 Attachment(s)
Here's the requested picture.

The more I think about it, the more I agree with the opinions above (not my own). At a minimum, a 2nd opinion from a few more roofers.

I'd rather step on the toes of my in-laws long-time roofer than just make a problem worse. I went up there to sweep the water off this weekend and the pond was bigger than it was in the past where it only extended from the right edge of the picture across 60% of that part of the roof (and wasn't as wide in the other direction, or as deep). We're also thinking of selling the house in the next year or so, and doing the wrong thing from a roofing perspective seems like a big risk.

I think the big problem for this roof is the kind of weird rectangle between the pitched roof and the pond. I need to make sure that drains even if we tear out the flat roof to add pitch.

To describe the picture, most of the area below the pond is an addition to the house (den and master bedroom). The flat roof without the ponding is over the covered deck that connects the house to the garage (which has a pitched roof). There is a slight ridge (that you can't see in the picture) between the torch-down flat roof over the house and the roll-down roofing material over the deck that prevents the pond from draining toward where I took the picture. I've never seen any ponding over the flat roof at the bottom of the picture.

1985gt 02-26-2013 11:43 AM

Basically what I would do is redo the whole thing, there is not enough info for us to say you could do one section or another, and honestly it's best to be done all at once. If there is no leaks and your going to sell it, I'd leave it unless there is a major issue it looks as if it would pass inspection.

mymrbig 02-26-2013 12:05 PM

There is one small area (maybe 10 inches across) that is quite soft, not to the point I would fall through, but it is very easy to make the roof give way by pushing on it.

We've also noticed a musty smell lately, though strangely not anywhere close to the soft spot and not under the part of the flat roof where the pond occurs (but instead where the part of the flat roof that doesn't pond in the center of the picture meets the pitched roof).

I'd love to wait and just let a new owner deal with it, but I also don't want the sale to fall apart because of the roof (which we were warned would be a potential problem when we bought it 8 years ago).

If I think I can get it on the market in 4 months, I'm thinking of just letting the new owner decide how to handle it. But I'm also worried with the soft spot and the smell that disaster could occur if I wait too long.

Thanks for your thoughts everyone, I'll keep checking it. This clearly isn't DIY for me, but I really appreciate the criticisms of the family roofer's approach if they are warranted.

jagans 02-26-2013 05:31 PM

You probably have fiberboard or Perlite insulation under the membrane that is soaked.

You are probably due for a tear off and new roof, but it is impossible to tell from here. If you want to take a core cut let me know and Ill walk you through it.

As 1985gt said you need to get the water off the roof. The problem I see with this setup is if you add tapered insulation it will bring you up onto the slope of the steep roof areas pretty high. Your low slope roof should run up slope at least a foot above the change of plane.

If that low area is still there once you tear off the roof, I would stick with my original recommendation to install a roof drain, except I would put in two 3 inch drains, after seeing your situation. You can use type A drains which are right angle type, and you can install them from the top by cutting out your sheathing. Keep in mind that the new sheathing must span three joists.

Of course You have to question why that area is low, and if it is a structural problem it must be addressed.

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