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fix for pooling water on a flat roof?

JFink's picture

Forgive me for the odd picture, I didn't have my ladder so I had to climb a tree to snap this quick photo. I would have gone out the window but the new owners of the house haven't closed the deal yet, and I didn't have access. Anywhooo...


The EPDM roof has some pooling water. Probably partially due to shady area.


What are my options for fixing this issue? It's finished living room below, so I'm not sure how I would increase the pitch without problems.



Justin Fink - FHB Editorial


Your Friendly Neighborhood Remodelerator

Justin Fink - FHB Editorial

(post #103891, reply #1 of 29)

Not much you can do with the existing, but when it's reroofed, use tapered insulation to get more slope. They make it in 4'x4' panels that slope from 1/2" to 1 1/2" and 1 1/2' to 2 1/2". If you use them in conjunction with 1" board, the dimensions are pretty much limitless.

(post #103891, reply #2 of 29)

whats that tapered insulation called? who makes it?


 


 

(post #103891, reply #5 of 29)

(post #103891, reply #16 of 29)

I've used " posi-slope" but it was a while ago and I don't know who makes it.


Its a fibre board product, custom made for each installation. Covered with a fibreglass fire protection mat and 2 ply torch down roofing.

If you didn't have time to do it right the first time, how come you've got time to do it over again?

(post #103891, reply #3 of 29)

Good thing is, it does not look like a huge area.I would think pull the existing roofing, rip some 2X material to correct roof framing for pitch & then re-sheet & re-roof.

(post #103891, reply #4 of 29)

taper system is the way to go, you dont need much to get run off 1/2" inch or so at the wall and down to nuthin on the edges. Building supply houses should be able to point you in the right direction

-worth exactly 2 cents!

If vegetarians eat vegetables, what do humanitarians eat?

(post #103891, reply #6 of 29)

I certainly agree that when it is reroofed the puddle should be eliminated with the tapered board.

But one question I have is how long does the puddle generally remain after a rain.

The last time I looked at instructions, the EPDM manufacturer wanted no puddles that lasted more than 24 hours.

So, less than 24 hours shouldn't be a problem...especially if there is no seam.

Rich Beckman

This signature line intentionally left blank.

(post #103891, reply #10 of 29)

Guideline I've heard is puddling after 48 hours is a problem. This is at least that long, maybe twice that.

Justin Fink - FHB Editorial


Your Friendly Neighborhood Remodelerator

Justin Fink - FHB Editorial

(post #103891, reply #7 of 29)

do it over again adding tapers.

 

 


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(post #103891, reply #12 of 29)

<< do it over again adding tapers. >>


Can't say I have much experience in EPDM...have you ever removed EPDM before? I've got to imagine it's not going to be much fun...


can layers be added to it like on the first or second go-round of applying asphalt shingles? or total strip and re-do?


Justin Fink - FHB Editorial


Your Friendly Neighborhood Remodelerator

Justin Fink - FHB Editorial

(post #103891, reply #13 of 29)

Either use tapered insulation or just the same thickness of insulation- mechanically fastened- then fully adhere the new rubber to the new insulation.


Leave the existing in place.

(post #103891, reply #14 of 29)

Depends

The ones I have torn up really didn't come that hard. Once started, the contact cement stretches apart, sometimes slit it a bit like peelong bark off a tree or skinning a deer, and it comes right along.

Keep the tear off piece. It makes a great tarp for over tools in the pickup truck or on the generator or...

you needen't tear it all off. use a sharp utility knife and cut about a foot back from the edge, take out the center and taper there, then tie the new to the metal or even place new metal and new back.

 

 


Welcome to the
Taunton University of
Knowledge FHB Campus at Breaktime.
 where ...
Excellence is its own reward!

 

 

Oh Well,

We did the best we could...

(post #103891, reply #8 of 29)

Get polyiso tapered roof board and get a 1:12 and hip it on that roof (to save you hassles at the drip edge).


Now, you could either put epdm back on, or you could go with a metal roof.


My first thought was to cobble up a 2x roof framing up there, until I started looking at how few courses of shigles were under that window, not leaving a lot of room for flashing the job correctly.


Occupational hazard of my occupation not being around (sorry Bubba)
I may not be able to help you Occupational hazard of my occupation not being around (sorry Bubba)

(post #103891, reply #9 of 29)

Justin,


Nothing really earth shattering, but I'll add a few comments. 


The roof appears to be about 10' wide (just a guess assuming the slider is 6/0 with ~2' on either side).  That small of a roof can be done w/o a seam.  I would check to see if there is or isn't a seam.  Assuming there is no seam or puncture, the EPDM membrane isn't adversely affected by the standing/ponding water.   


It would be better to have the roof slope and move the water to the gutter, but I wouldn't replace the roof solely to eliminate that ponding water.  With three exposed edges, it really can't build up that much.  


Are there other reasons to consider replacement?  Any leaks??

 

(post #103891, reply #11 of 29)

<< Are there other reasons to consider replacement?  Any leaks?? >>


Bingo. Small water damage in the room below. It may be closer to the where the chimney contacts the house, It's too close to tell.


Either way, standing water doesn't make me happy.


Justin Fink - FHB Editorial


Your Friendly Neighborhood Remodelerator

Justin Fink - FHB Editorial

(post #103891, reply #15 of 29)

If the water damage is close to th echimney, then the chimney itself or its flashing could be your problem. I waould be sure of that first.

As far as puddling goes. I am far more comfortable with puddling on EPDM on such a small roof with no seams than with any other roofing membrane.

But it still do3es allow minor permeability. I forget the rating on it, but if you baged water in it and held it there, it would eventually sweat some out.

 

 


Welcome to the
Taunton University of
Knowledge FHB Campus at Breaktime.
 where ...
Excellence is its own reward!

 

 

Oh Well,

We did the best we could...

(post #103891, reply #17 of 29)

It occurred to me that you could put in a drain in the middle of the roof.

Of course, that would require access to the underside of the roof...

and you'd have to run the drain out of the side and to somewhere...

But it can be done.

Rich Beckman

This signature line intentionally left blank.

(post #103891, reply #18 of 29)

you know...that's a pretty unconventional idea, but it's not all that bad. I'll have to give it some more thought, and check to see that the chimney isn't the point of leakage...but it's definitly worth tossing around as an option. Thanks!

Justin Fink - FHB Editorial


Your Friendly Neighborhood Remodelerator

Justin Fink - FHB Editorial

(post #103891, reply #19 of 29)

>>>>>>>>>that's a pretty unconventional idea, but it's not all that bad.

Let's see here: collect the water that you're trying to keep out of the house and bring it in the house. What part of that is "not all that bad".
I've probably had to fix about 20 of these type brainstorms in my career. I know it's common on large commercial roofs, but in your scenario it's pure folly.

(post #103891, reply #26 of 29)

"I've probably had to fix about 20 of these type brainstorms in my career."

Although I wasn't being all that serious when I made the suggestion, I don't see how you fixing 20 of them is all that relevant.

I've repaired countless asphalt shingles.

That doesn't mean an asphalt shingle can't be a good roof.

It does mean that it should be installed by someone who knows what they are doing (and I think every time I've repaired a roof, it was clearly installed badly).

Whether it is shingles, rubber, metal, flashing or roof drains (windows, siding, doors, cabinets, flooring, etc., etc) there are plenty of people out there installing it without really knowing what they are doing.

Rich Beckman

You are here

(post #103891, reply #27 of 29)

Just the fact that the drain exists is a problem and one that is more likely to cause trouble than to help things out on this partiicular roof.

One of the things holding water back right now is the extra thickness of membrane material around the perimeter where the metal trim is nailed and then stripped off
That creates a dam to hold water on a flat roof.

The same thing exists arond a roof drain. It has to be sealed to the membrane with at least one other layer of material. Then most good drains have a debris curb that will also cause water backup around it another 1/4" to 1/2". On commecial installations, things are designed and pitched to the drain to minimize that probalem.

Then remember that one main advantage of the EPDM single ply roofing is fewer seams since any flat roof it is usually the seams that are the source of leaks. By adding a drain, you punch a hole in the roof and then seam around it.

So in effect, you do not reduce the puddling, plus you add a potential 'flaw' right in the middle of the puddle.

The reason roof drains leak is only half from bad work. The very concept is poor design most of the time.

They are also very expensive to build in. Probably at least as much as this whole little roof.

 

 


Welcome to the
Taunton University of
Knowledge FHB Campus at Breaktime.
 where ...
Excellence is its own reward!

 

 

Oh Well,

We did the best we could...

(post #103891, reply #28 of 29)

(post #103891, reply #29 of 29)

I tried to avoid it the other day - but I had a headache then too...

 

 


Welcome to the
Taunton University of
Knowledge FHB Campus at Breaktime.
 where ...
Excellence is its own reward!

 

 

Oh Well,

We did the best we could...

(post #103891, reply #20 of 29)

No
nO
No

Just trust me - NO ROOF DRAIN!

 

 


Welcome to the
Taunton University of
Knowledge FHB Campus at Breaktime.
 where ...
Excellence is its own reward!

 

 

Oh Well,

We did the best we could...

(post #103891, reply #22 of 29)

ya know...it seemed like an interesting idea first thing this morning. But a cup of coffee and a little bit of consideration later...I think you're right. It's a pretty scary thought!


Luckily I'm not afraid to admit that I don't know everything about building...far from it! Thanks Piffin.


Justin Fink - FHB Editorial


Your Friendly Neighborhood Remodelerator

Justin Fink - FHB Editorial

(post #103891, reply #21 of 29)

I can understand why YOU would want one with all those chickens and cows and rabbits needing a place to flush though.

;)

 

 


Welcome to the
Taunton University of
Knowledge FHB Campus at Breaktime.
 where ...
Excellence is its own reward!

 

 

Oh Well,

We did the best we could...

(post #103891, reply #23 of 29)

Let me first state I am an engineer, not a roofer, so I don't have a lot of experience with EPDM roofing. However, I roofed my garage with it a few years back and read up on Firestone's products and methods extensively before doing the work.


Do you know if the roof is fully adhered?  It could be fully adhered (glued down), or it may just be glued around the edges or even mechanically fastened through the gravel stop ("drip edge"). 


If it's not fully adhered, you could remove the gravel stop and insert a tapered cant under the middle of the roof - or even slide in some of the tapered foam insulation.  You really don't need much slope to eliminate ponding - 1/4" per foot is sufficient, maybe even 1/8", so a slight "bump" in the middle may well be enough to solve the problem.


If it's fully adhered, you could still do the same thing, but since you would have to completely remove the membrane anyway, it's probably not cost effective from a labor standpoint to do it that way.


If you do replace the membrane, look into some of the alternatives such as TPO before choosing EPDM.  The solar gain from EPDM is a lot more than I would have expected, the white color of some of the alternatives would be a huge help.


I assume you also know that the manufacturer won't warranty the install unless they certify you?


The other thing that really annoyed me is that my supplier will only sell it by the roll.  I needed 600 square feet, so I have to buy the 1000' roll and now have 400' left over.  Anybody need some EPDM in western PA :-)  (Firestone sells in 500' and 1000' rolls)

(post #103891, reply #24 of 29)

Thjere is nothing better for tarping down tools in the truck!

EPDM can be had in white if heat gain is an issue.

Your idea of removing just the edge metal has no merit IMPO. That is 2/3 of the work right there.

He could slit center and peel back enough to insert some tapers tho and re-apply more EPDM over the central portion though.

 

 


Welcome to the
Taunton University of
Knowledge FHB Campus at Breaktime.
 where ...
Excellence is its own reward!

 

 

Oh Well,

We did the best we could...

(post #103891, reply #25 of 29)

Scrubbing the field rubber to get it clean enough for another sheet to bond properly is a pain!