Another flat roof - Mod Bit?

[Kyle Kubs]

I see these so rarely I can educate myself on them and then forget it all by the next time I come to one.

1) I make this material to be torch down Modified Bitumen?

2) Normal life span is around 25-30 years? This one was still quite soft underfoot and the alligatoring was there but not at all heavy so I'm guessing it is around 5-10 years in age.

3) Now the real question. Where it meets the ridge of the shingled roof I would expect it to overlap the ridge, not be under it the way it is. I figured maybe they did that and then put the ridge shingles over it to hide it but when I lifted the ridge shingles it wasn't visible. Is this wrong?

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Download Attachment: 021.jpg

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[Brandon Whitmore]

Looks like mod. bit.

I was thinking that mod. bit. had a life expectancy of around 15- 20 years, but I think it may vary quite a bit depending on a lot of factors such as slope, whether it is coated/ maintained, etc. I just looked up life expectancies on- line because I was curious--- looks like anywhere from 15-30 years.

I'd be concerned with that detail as well, but don't have anything to back it up.

[caryseidner]

Kyle -

It does look like APP (Torch Applied) Modified Bitumen. The manufacturer warranties it for 10 years, unless a surface coating is applied (an re-applied as it wears) in which case you get 12 years.

There needs to be a transition flashing between the flat and pitched sections. The diagram below shows the transition flashing that would be used for a BUR and gravel roof - shingle roof, and it would be correct for your roof as well. However the vertical rise in the metal gravel stop could be eliminated since there is no gravel on your roof.

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[Brandon Whitmore]

Hi Cary,

That's the detail that I think should be there, but it shows where the flat roof is draining onto the sloped roof. I think, may be wrong, that Kyle's pic. shows the roof sloping away from the sloped roof.

Of course, when snow starts to melt and pool up, the water won't care that it is supposed to drain the other way.

[Kyle Kubs]

That was my concern as well. The rain should not give it a problem but with snow sitting up there it can easily turn into one. And if someone gives it a white sealer coat to help it last longer then the snow issue will get worse.

Brandon, the 15-20 year life span is what I initially believed also, in broad, general terms, but had done some googling myself and was finding roofers claiming 30 years. I think I may stick with the 15-20 given our climate.

Cary, Thanks for the info & diagram.

I've never seen one sloping toward the shingled roof unless the design didn't allow any other way. Not sure I would like that if I did.

[caryseidner]

Yea the slopes are different, but the metal flashing detail is the same. Just bent at a different angle.

[qhinspect]

I've seen the same install around here that's in picture 026. I went to a well known union roofing company (I did an inspection for the owner) and he informed me that the type of install is considered acceptable. I to was a little surprised but when I went to another roofer and informed him of what the owner of this other company told me, he agree with what I was told.

I don't know the slope of the roof in the pictures but there was a small pitch away from the roof shingles.

I still don't like it.

[kurt]

I don't like it either, but I will grudgingly admit that it works fine if the shingles are sealed to the membrane.

Reason I say, I see this a fair amount in the City; there's a lot of shed dormers on old bungalows and capes around here.

[Kyle Kubs]

I had a feeling someone was going to come along and say that.

It would probably bother me less if there was a way to get under this area in an unfinished space and see the sheathing, but by it's very nature, it's finished space underneath.

This is the first I've seen it configured this way, typically the shed hits the sloped roof several courses down from the ridge instead of right up to it like this.