Gap in roof flashing?

[Steve C.]

Roof flashing over the roof of the front porch had about a 3/4" gap under it. Wood blocking about every 16" or so supported the flashing. The builder said there was screening to help vent. My question is if there was a driving rain storm, wouldn't it go under the flashing through your "screened vent" and down into the closed soffit area above the front porch? He says no because there is a negative pressure. What the? I have a picture but its from a distance, but maybe it will help in what i'm trying to explain. I've never seen flashing propped up like this. He said he used to do this in Seattle to help keep moisture and mold from under the flashing. ?? Comments.

[Billy Stephens]

Roof flashing over the roof of the front porch had about a 3/4" gap under it. Wood blocking about every 16" or so supported the flashing. The builder said there was screening to help vent. My question is if there was a driving rain storm, wouldn't it go under the flashing through your "screened vent" and down into the closed soffit area above the front porch? He says no because there is a negative pressure. What the? I have a picture but its from a distance, but maybe it will help in what i'm trying to explain. I've never seen flashing propped up like this. He said he used to do this in Seattle to help keep moisture and mold from under the flashing. ?? Comments.
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I guess if the Driving Rain was going up 30 degrees.
.

[Jerry Peck]

That *may* be a counter flashing, and, if it is, then no problem.

If that *IS* THE flashing ... then it in installed all wrong.

[Steve C.]

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I guess if the Driving Rain was going up 30 degrees.
.

I've seen some thunderstorms where the rain goes almost upside down. And, I've been called back to a home where a situation (and driving rain) went into the attic area and dripped down through the pendant lights onto the cell phone sitting on the counter. I was asked why I didn't call out that gap in the eave. Small gap I might add. Just trying to cover my a**

[Steve C.]

That *may* be a counter flashing, and, if it is, then no problem.

If that *IS* THE flashing ... then it in installed all wrong.

Thanks Jerry. Love this website.

[John Kogel]

Right. I would definitely point out the potential for moisture to get in. We see rain splash a foot up the wall quite often.

The purpose may be to ventilate the enclosed attic spaces there. If so, he should install a ridge vent which is designed for the purpose.

[Door Guy]

Right. I would definitely point out the potential for moisture to get in. We see rain splash a foot up the wall quite often.

The purpose may be to ventilate the enclosed attic spaces there. If so, he should install a ridge vent which is designed for the purpose.

Take a look at the picture again. It would be a little difficult to install a ridge vent in that situation. Maybe some pancake/pot vents would have been a better choice, but I don't like those either.

[Eric Barker]

He says no because there is a negative pressure. ?? Comments.

He's right about there being a negative pressure. With a wind driven rain there's a negative pressure in the wall and an positive pressure outside. The wind and pressure differentials can drive water pretty far into a structure. Without some dis-assembly you're not going to know how protected things are. Nothing wrong with writing what you see and what you don't know.

[Darrel Hood]

This may be a good solution to ventilating the porch's attic, but I would comment that it is an abnormal installation that may lead to water intrusion under some circumstances.

[Door Guy]

I believe something like this is what you are seeing. Roof-2-Wall (http://www.roof-2-wall.com/)

[Garry Sorrells]

The method for the venting may work and resolve a problem, but just not a complete design to meet need. There needs to be something to physically prevent water from blowing in. Below is my solution though I would question distance from edge of flashing to wall as being adequate. If an extention swas needed an extension could be riveted on to existing material.

The Ridge Vent For Shingle Roofs

The RidgeVent for Shingle Roofs | Specifications (http://www.theridgevent.com/specifications.html)

• Size: 20' x 10.5" x ¾" / 6.096m x 266.7mm
• 14.1 Sq. In. of Net Free Area per Lineal Ft.
• Vent Material: Non-woven, non-wicking matting, UV stable.
Specially formulated pressure sensitive adhesive will adhere to
roof shingles.

[Roofmaster 417]

With rain it might be a good argument but Ice ???,,,now that is a whole different story.Somebody has negative pressure between the ears IMO.

[Glenn Duxbury]

Hi, ALL &

It "appears" this was an attempt to do a rain-screened wall assembly - except the wall flashing should be the lowest piece (anything emptying from inside that vented drainage path should flow over - not under).

Botch-job...


Cheers !

[Garry Sorrells]

After allowing this to sink in I have to question what the Builder was trying to say in "...He says no because there is a negative pressure ...". Negative pressure from what against what???? May have lost something in the translation.