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Old 06-13-2009, 07:50 AM  
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Default Foam for flat roof - viable for residential use?

I have a townhome whose roof is 18x44 feet. The roof deck itself is reinforced concrete, with built-up roof that's approximately 10 years old (according to the guy who sold the house to me last year). I've always had a major humidity problem (with 90pt/day whole-house dehu, I can get the house down to 45% when it's not raining, and 50% when it IS), but blamed the central A/C up until yesterday. Meanwhile, I've known for a few months that the upstairs bathroom has a major mold problem, which I've historically blamed on the broken exhaust fan and idiot previous owner's use of vinyl-backed wallpaper in the bathroom. I knew there was mold inside the wall where the exhaust fan was, but thought it was due to the duct being blocked and blowing hot, moist air into the wall cavity.

Well, earlier this week I started gutting the bathroom to eliminate the mold and fix everything once and for all. I got the drywall off the fan's wall, and what I found is shown in the first and last pics (the electrical box is for the light over the sink in the master dressing area on the other side). It quickly became obvious that water is coming in through the fan's vent shaft.

As of yesterday afternoon, my theory was that the duct was either missing its flashing, or had been removed entirely and roofed over (when cleaning out the duct, big chunks of tarry gravel came out). I was almost at the panic stage, because it occurred to me on my way to work that I might have actually punched a hole through a roof patch, and would have water pouring inside the next time it rained. I bought a ladder, made it up to the roof, and was simultaneously relieved and anguished by what I saw.

The good news is that the vent did have proper flashing and a cover, so if water is going to come in the next time it rains, it doesn't look like it will be any worse than it's been for the past few years. So at least I didn't escalate this from "problem needing repair" to "crisis" by cleaning out the duct.

The bad news is that the roof was under at least an inch of water nearly everywhere, and had a few large, very soggy and waterlogged blisters -- one of which was a few feet away from the duct in question. I'm now guessing that water is getting under the roofing, and making its way under the flashing to the duct... quite possibly, elsewhere in the house as well.

OK, time to discuss repair options.

I really, REALLY want to get the roof covered with sprayed-on EPS foam (the dense kind used for making ICF forms). Apparently, it's waterproof, provides just about the best insulation you can get, and "maintenance" consists of having more foam sprayed on if something like a hurricane or damage from the rooftop A/C's replacement dislodges chunks of it. The problem is, I've NEVER been able to get one of the few companies in Broward County with web sites claiming to do EPS roofing to ever return a call, and have a hunch that this might be one of those things that's a nearly ideal solution for flat concrete roofs... but cost-prohibitive unless you're talking about something like a multi-acre roof on a mall, plaza, school, etc.

Does anyone have any idea how the cost of EPS compares to alternatives, like IB (PVC) or conventional BUR?

Alternatively, if EPS is do-able, but way more than I can afford right this minute (or can't be done in the summer when it rains nonstop), do I have any viable DIY options that are likely to patch it well enough to eliminate the leaking for at least a few months (if I can do EPS in January or February when there's no rain) or a couple of years (when I'll be in a better financial position to afford EPS, even if it IS hideously expensive)?

The biggest problem I see right now with trying to patch it myself is the endless daily rainstorms we'll be having until November or December. The only idea I've come up with so far is to try and use sandbags to dam off a 10x10 area at a time, try to keep that area covered with plastic , and try fixing it a piece at a time, starting with the center and working my way towards the front and rear (there's a slight slope downward towards the front and rear, where there are drains emptying into gutters). I'm aware that elastomeric paint exists, but I'm not sure whether they can be applied anytime over the next few months due to the endless rain -- even if I WERE able to partly dry off a 10x10 area at a time.

Any ideas? The one bright spot here is that I DO have a concrete roof deck, so if I can at least somehow seal off the roof penetrations, I'll be 99% of the way "home". In fact, one Idea that occurred to me (no idea about cost effectiveness) was to strip the BUR altogether, build concrete "islands" around the penetrations, coat the entire roof (including the inside of the penetrations with Xypex (a concrete waterproofer that gets soaked up into the concrete matrix, then chemically bonds with any water that gets through to form crystals that physically block the passage of more water), fill the voids inside those penetrations with expanding foam sealant, and finish by painting everything with 2 or 3 coats of elastomeric paint. In theory, it seems like it would work... but I've never heard of anyone doing it, and suspect there's probably a good technical reason why (or possibly a building code requirement that this solution elegantly engineers an alternative solution to solve the original problem, but wouldn't be allowed just because that's the way the law is written).

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Last edited by miamicanes; 06-13-2009 at 08:15 AM.
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Old 06-13-2009, 03:44 PM  
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HI Miami!

I'd like to tell you I have a solution to this problem... but I dont.. although the much wiser ones will be around shortly to help you with that... but, I do know that that is ALOT of mold/mildew..... I hope you wore a respirator and remember that you've got to clean ALL of that off with a bleach solution. I think I would also swab a sample and send it off to make sure that there is none of the potent black mold in there.

You will have to use bleach and water and scrub the 2X4's and drywall and such, and then... you will have to let it completely dry.

I hope someone comes along soon to help you out with this so that it doesnt get anyworse and good luck with this project and again welcome to the forum

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Old 06-13-2009, 05:15 PM  
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Well, I just got back from Home Depot ~2 hours ago, after picking up a sweet St. Louis brand 24' 300#-capacity fiberglass extension ladder for $110 (closeout special). I went up on the roof again, was happy to see it looking a LOT drier than yesterday, and shot some new pics.

The bad news is that for now, it looks like foam is financially out of the question (though I'd still love to know the cost, because I want it eventually), and I'm going to have to settle for patching up the existing roof myself.

Basically, every seam is bad. There are puffy blisters and lots of alligatoring everywhere. And what's theoretically supposed to be the highest part of the roof perversely seems to be the lowest.

I have a lot to learn about roofing, but I guess my current high-level plan is to slice and seal the blisters, build dams around the penetrations, try to give the roof a consistent downhill slope from front to rear, and finish it off with 2 coats of white elastomeric paint. Anyone know any good books available from Amazon that do a good job of addressing the topic of built-up roof repair (what to do, what NOT to do, how the different products available from Home Depot & Lowe's work together, etc)? The two I saw at Lowes Depot(tm) only dedicated 3 or 4 pages apiece to the topic

Onward to the pics:
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Last edited by miamicanes; 06-13-2009 at 05:17 PM.
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Old 06-13-2009, 06:40 PM  
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I didn't read your whole post, but I know a little about flat roofs, and I can tell you that it is COMMON to use expanded foam when making a "sloped" roof.

A sloped roof is NOT the same thing as a shingled roof that relies on a steep slope to prevent the rain water from running under the shingles. When a roofing company makes a sloped roof, they start with a flat roof and make an accurate drawing of it's dimensions and the locations of any roof drains or scuppers.

Then they feed these dimensions into a computer and tell the computer where they want the drainage valleys to be. The computer then generates all the parameters to cut 4 foot square foam slabs of varying thickness. These parameters are fed into a computer controlled machine that cuts each slab with a hot wire. Sometimes the same slab has to be rotated in the machine and cut several times, for example at the bottom of a valley where the two slopes meet. The computer controlled cutter cuts all the foam slabs so that when the slab are laid down in order on the roof, the top of the foam will have "valleys" in it that slope at 1/4 inch per foot toward the center of the valley, and the valleys will flow to the drains or scuppers on the roof.

The advantage of having a sloped roof is that even if you get a roof leak, you won't have as much water damage because water won't "puddle" on a sloped roof; it'll flow to one or the roof drains or scuppers. Also, having a sloped roof means that you pay more up front, but thereafter every 25 years when you redo the roof, you end up with another sloped roof at no extra charge.

After they put the styrofoam slabs down in order, they cover the styrofoam with two layers of fiber board and then mop down hot asphalt and roll asphalt impregnated felt paper into that hot asphalt. Typically, they'll have four plies of felt paper with an additional two to 4 plies around the perimeter of the roof.

The reason they put TWO layers of fiberboard down over the foam is two fold. If they put only one layer down, the 300 deg. C asphalt they mop down would seep through the joints between the fiberboards and melt the foam. By using two layers and staggering the joints, this is avoided. Also, when it comes time to re-roof, they can pull off the top layer of fiberboard and have a clean layer of fiberboard underneath. They then just put another layer of fiberboard down and start mopping the felt paper on. That way they never have to walk directly on the foam (which might get damaged).

So far as mildew growing on your bathroom walls goes, that might just be due to condensation forming on those surfaces. If that's the case, you can prevent mildew growth on those painted surfaces by using a paint specifically intended for bathrooms like Zinsser's PermaWhite Bathroom Paint available at Home Depot and other paint retailers.

Bathroom paints have mildewcides in them that are highly soluble in water. Because of this affinity for water, the mildewcides in the paint will migrate through the dry paint film to the surface of the paint if the paint gets wet or even under conditions of high humidity. The mildewcides are slow to migrate, but they are very effective. As a result, the painted surfaces stay free of mildew for a long time. Zinsser's guarantee's their PermaWhite bathroom paint to be free of mildew for a minimum of 5 years. My own experience is that this paint stays mildew free for very much longer than that.

I own a 21 unit apartment block in Winnipeg, Manitoba, and I have a sloped roof on my building, and all 21 bathrooms in my building have Zinsser's PermaWhite Bathroom Paint on their walls. There is no mildew on any of the walls or ceilings in any of my bathrooms, and I can assure you that it isn't because all of my tenants wipe down their walls and ceilings with a dry towel after every shower or bath.
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