Strange roof valley condition in New Orleans


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Old 01-07-08, 11:33 AM
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Strange roof valley condition in New Orleans

I have limited construction experience, and I am now project-managing for a nonprofit group, and we have a unique roof condition and I really have no clue how to handle it - I can't seem to find a standard detail to deal with it. The house will be located in New Orleans.

This is a rendering of the house: http://i13.************/7xt7i1g.jpg

I can post a roofplan/elevations/anything else, if there's more info needed. It is a valley that is perfectly horizontal across the width of the house; in other words, the valley itself has no slope. Any ideas?

Thanks,
Melissa
 
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Old 01-07-08, 12:18 PM
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Melissa,

My $.02 worth: that roof is asking for trouble.

A butterfly roof's horizontal valley is difficult to keep clear of debris and prone to leakage, so this type of roof requires more attention than many homeowners want to give it.

And, where is all the water going after it runs off that roof?

It's difficult to collect water at that point and the collector box and flashing will be prone to clogging, so unless the rake edge and/or fascia/soffit junction in this area (and elsewhere) is designed to prevent it, water will be running along the fascia and soffit and down the wall of the structure.

If the designer didn't bother to draw this detail, they may not thought this through - and this is exactly the kind of detail that if left to the discretion of the a typical roofer creates water infiltration nightmares.

Also, that roof profile is likely going to act as an airfoil and generate considerable uplift when Katriina's sister come to visit - has this been calculated and the structure designed with this in mind?

If you still want to roof that as designed, ask and established local commercial roofer for membrane and flashing recommendations.

Good luck with your project!

--------------

"Just because an architect can draw it, does not mean it's wise to build it as drawn."
 
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Old 01-07-08, 02:12 PM
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This condition is similar to having a chimney along the wall at the end of an eave. Any appreciable length of this junction needs a cricket to help shed the water, or else the long term health of the roof is compromised.

If the design will not change, then I agree with Michael about enlisting the services of a commercial roofer that does flat roofs with membranes early on in the construction phase.
 
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Old 01-19-08, 12:35 PM
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Melissa,

Here's an example of a "cricket" of the sort mentioned by Kestas at the intersection of two planes on a "butterfly" roof profile:

 
 

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