Q on EPDM corner detail

Hi All,

I'm a homeowner who got some good technical info and advice about replacing my roof on this forum, back in 2005-2006. I ended up with an EPDM based roof. I'm hoping to get some more detail and advice about a corner detail of that roof.

I've noticed recently that there is accelerated wear on the wood siding below this corner, and after look carefully at the construction of the roof in that corner, I believe that during heavy rains, there is probably water leaking out below the metal edge but above the EPDM in that corner. The way this roof has been constructed, the EPDM is stretched over a sloping wood cant at the edges and covered with folded metal. At this outside corner, the metal from the two sides meets at a sort of a bevel with a tiny overlap. I can easily stick my finger between the EPDM and the metal. There is just an air pocket there. Theoretically, tapered insulation should draw water away from the corner, but this is corner is on the low side of the roof and the insulation that was installed was cut by the roofing crew rather than Firestone, and it seems to have little plateaus rather than a smooth slope everywhere. I'm guessing that the cant itself is probably not ideally constructed for this corner and may not have provided any slope for the EPDM to ride up. The roofing crew did rebuild my cant in other sections of the roof where there was tree damage or it was deemed necessary for tapering. I think it's likely they re-used the previously existing wood at this corner, but I'm not really sure about that. A constraining issue of the project was to add insulation without substantially increasing the amount of face metal over the existing siding.

I had another flat roof on my house installed by a different company in 2009. On that roof, while they were also using the same type of Firestone metal, they added a layer of EPDM that rides up the metal on the part that faces the roof , so this issue could not arise in with their method of doing edge details.

The 2006 roof I am asking about came with a ten year warranty, I'd like to get your collective advice on whether I should:

1) do nothing and live with it 2) do something about this myself ( if so what?) or 3) ask the company that installed the 2006 roof to perform warrantied service or 4) ask the company that installed the 2006 roof to perform non-warrantied service or 5) ask another company to do something.

Hi Vaa,

Did you go by MikeNZ around here at one time? If so, then "Hi" to Mike and your wife.

I don't have any liquid rubber but I'm sure I could get some. There wasn't any formal design process for this residential roof. I met with an estimator and told him I'd like as much tapered ISO as possible but I didn't want to make the face metal on the outside much taller than it was. He came up with an estimate that included replacing some, but not all sections of the existing cant. The amount of detail I got was that level of avg. 1/8 inch per foot slope of taper and location of the scuppers. The only part of the cant I actually saw from the old or new roof was the exposed part on the back where my falling oak tree had broken through. The crew chief who worked on the roof would have had discretion over the corner detail.

The estimator who I worked with on the later 2009 roof made a good point about retrofitting more insulation to my type of house. His suggested best practice was to involve a subcontractor to blow foam down through the decking into the cavity below, allowing for more insulation and putting the de facto vapor barrier closer to the warm side.

Hi Egg,

Hope you and your family are well. My daughter, Riley, is starting first grade on Tuesday. Can't remember what I said about her a few years back, but she was an early reader, and these days she reads for pleasure. The "Ramona" books are some of her favorites, though she's also read heavier books like the Little House on the Prairie series.

I'll try to post a picture this weekend. At the same time, I'm going to try and test what happens if I take a hose up on the roof and gently point some water at that corner.

A picture would be helpful. By the way, I remember your last visit here; enjoyed it. Is your youngster still expanding her(?) vocabulary at lightning speed?

This is, of course, impolitic in this industry, but I don't care. Cant strips (in the real world... not the political one) are irrelevant if the materials are handled and installed with respect (call it love if you wish) so if you have water working between the membrane and the cap metal, your fascia height is obviously insufficient.

Call them up and see what they say.

Yeah, I suspect the cant probably wasn't mitered together, though of course I can't see it. I suspect there is just a gap between the cant from one side and the cant from the perpendicular side. The same guys did the EPDM and the metal at the same time, but I think they reused the cant in that location from the prior roof. The prior roof had less insulation (and was tar and gravel) so the cant height would have been less of an issue.

Yes, circumstantially I believe water is probably running between the metal and the rubber at this corner when the water level on the roof is high enough, due to a heavy rain - it's obvious on the roof that the water can run under the metal but it is circumstantial that it can exit the other wide of the metal and run down the side of the house. There is no stain to wash - this is only an issue on the exterior. There is just more peeling and cracking of the wood siding at that corner than in nearby locations.

The warranty is still good on the roof, but I'm asking opinions about whether this should be considered a warranty issue or just a performance issue.

If I were going to fix it myself, would I use the same kind of foam that is used for cavities around windows? Maybe put some polyurethane over that?