Roof-to-Porch Transition, advice request

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Old 06-01-12, 08:03 PM
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Roof-to-Porch Transition, advice request

Hooray - the building inspector passed my sheathing inspection (some excess space between boards, but acceptable)!!

So, finally, I can go ahead with underlayment, etc

But, I'm wondering how to deal with my porch.

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I don't think I'm the only one who has reservations about rolled roofing.

The roof slope is 5/12 and the porch is 1/12.

The city inspector suggested I just go with my 3-tab Malarkey Alaskans (put ice & water shield down first with extra overlap). This will not be covered by warranty, but I'm not to concerned with that.

But, what about the valley?

I want an open-cut valley (ice & water plus galvanized steel).

Also, I want to bridge the roof/porch transition with galvanized flashing (I&W first; flashing and then Tri-Flex underlayment over the metal.

This is Denver - not a huge amount of rain or snow (accumulation of maybe a foot of snow - at most).

I'm just trying to picture the valley -
Since we don't get a huge amount of rain or snow - I guess there is no problem with an open valley streaming down onto the porch shingles? - I just need to make sure the porch shingle has a full tab at the bottom of the valley?
Maybe I need to extend the valley metal out a little further over the porch to spread the impact of water coming down the valley?


You can see more shots here:
valley - to - porch - a set on Flickr

And some shots of the deck, after tear-off:
Porch - post tear-off - a set on Flickr

thanks for everyone's help - starting to see some light at the end of the tunnel
 
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Old 06-02-12, 05:49 AM
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Flashing, flashing, flashing. You gotta stop capillary action at the transition somehow. Flashing will need to go under the house roof and over the deck roofing enough to stop backup.

This is Denver - not a huge amount of rain or snow (accumulation of maybe a foot of snow - at most).
Not sure which part of Denver you live in, but I have seen my grandkids' standing with only their noses above showing. I can't imagine a 1:12 pitch roof in that area.
 
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Old 06-02-12, 08:06 AM
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"Flashing will need to go under the house roof and over the deck roofing enough to stop backup."

Thanks Chandler.
So, to say it another way: Flashing to cover the transition between roof and porch. First cover porch and up onto the roof deck about 18" with ice & water shield (adhesive, self sealing, rubberized asphalt). Then cover that transition area with flashing (20" wide galvanized steel). Then cover with Tri-flex underlayment and then shingle?

Or, should flashing go down first?
 
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Old 06-02-12, 04:49 PM
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We don't use the membrane too much here in the south, so I'd have to defer that order of business to some of our yankee pros, or even Canadian
 
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Old 06-02-12, 10:12 PM
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The city inspector suggested I just go with my 3-tab Malarkey Alaskans (put ice & water shield down first with extra overlap). This will not be covered by warranty, but I'm not to concerned with that.
Does that mean that Malarkey doesn't warrant the Alaskan to perform, i.e., drain water, on a 1:12 pitch roof? If so, then you're essentially relying on the underlayment for protection and laying the shingles for a finished look, right?

When you talk about "the valley," are you talking about the horizontal transition from the porch to the main roof? That should be doable with the membrane and a release layer from the porch eave to maybe 3' up onto the main reef, plus continuous shingling from the porch eave to the roof ridge. Is there a diagonal valley above the porch roof, draining onto it, that you're wondering about?

I used a membrane as the first layer under a metal-shingle roof some time ago, on the lower, bell-cast portion of the main roof. The pitch there was below the minimum at which the shingle manufacturer would warrant the performance of their product. The full system - solid sheathing, the membrane, a release layer and the metal shingles - actually performed better than we'd expected.
 
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Old 06-02-12, 10:52 PM
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Does that mean that Malarkey doesn't warrant the Alaskan to perform, i.e., drain water, on a 1:12 pitch roof?

Malarkey:
"Do not apply shingles on roofs having a slope less
than 2" (51 mm) per 12" (305 mm)."


then you're essentially relying on the underlayment for protection and laying the shingles for a finished look, right?

Yes, I suppose that's what it amounts too (its a front porch).

I'm concerned about both:
- that diagonal 11' valley that empties onto the porch
- and the 1" gap / transition (varies) between roof and porch

Can you describe the "release layer"? Is that the flashing I will use to bridge the transition from roof to porch (20" wide galvanized)?

Yes, the sheathing is 1x8 boards (not OSB).

Maybe it will make more sense for me once I start laying it down.
Valley will be "open" over galvanized steel.

Thanks for your input.
I may be trying to do this Sunday or maybe Monday.
Any further insight would be much appreciated.

Photos:

valley - to - porch - a set on Flickr

Porch - post tear-off - a set on Flickr

Valley, mid tear-off - a set on Flickr
 
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