Can J-Channel keep water off wall?

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Old 08-30-14, 07:31 AM
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Can J-Channel keep water off wall?

I don't understand how the Vinyl siding system works to keep water away from the wall any place there is J-Channel. The way it appears to me is water gets inside of the J Channel, water runs down both sides of the siding, and since the inside surface of the siding is in contact with the wall under the siding, the wall gets wet. Am I missing something or is this just how the system works?

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Edit: I found an example of how to flash with aluminum.
 

Last edited by IT_Architect; 08-30-14 at 07:52 AM.
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Old 08-30-14, 08:20 AM
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Personally I go crazy with flashing, however, it is normal for water to get behind the vinyl siding. The key is the house wrap behind the vinyl. It is supposed to be a water barrier, but must allow moisture vapor to pass through it from inside to outside.

Two tricks I use, and I'm not a pro at this, are one, I overlap the bottom section of flashing onto the top edge of the vinyl. Any water flowing down from above is directed back to the surface. And two, any two flat surfaces in direct contact will allow water to flow sideways or even vertical via capillary action. By adding a vertical crease to the side flashing I create a break between the siding and the flashing and prevent any water from being siphoned beyond the crease. The ridge on some steel roofing has a capillary break built in.

Bud
 
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Old 08-30-14, 08:38 AM
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By adding a vertical crease to the side flashing I create a break between the siding and the flashing and prevent any water from being siphoned beyond the crease.
That sounds like something I can use.

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Old 08-30-14, 03:08 PM
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I overlap the bottom section of flashing onto the top edge of the vinyl.
Yeah I do something similar. Take a 12x12 piece of flashing, cut a corner out of it, place that cutout around the bottom corner of a window sill, then put the j-channel on top. Siding then goes behind the flashing, and it's cut to length so that it lays over the nailing fin of that full course of siding below the window. That way it directs water out to the weep holes as soon as possible. Probably not perfect but if it keeps 99% of that water out, that's better than doing nothing at all, which is what most guys do.
 
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Old 08-30-14, 07:25 PM
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which is what most guys do
And that's what I was seeing, and that's why I asked. People worry about the OSB they have behind there, but this building has sheet rock outside walls, a fancy word for plaster board. The wood siding that was on there would naturally keep it dry, but not vinyl.
 
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Old 08-30-14, 07:35 PM
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For many years code didn't "require" a WRB behind vinyl siding but back in about 2006 they wised up and put it into the IRC.

That doesn't help all the people who either had homes built prior to 2006 or who had contractors with no common sense. I mean really. Who would skip the housewrap to save a few bucks? Oh, you're right. A lot of guys would.



Thankfully the gypsum sheathing you have probably seen is a lot more resistant to moisture than OSB is. It is not the same product as interior drywall.
 
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Old 08-30-14, 08:01 PM
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I replaced the bottom two feet because it crumbled to pieces. Animals were forcing their way under the cedar siding breaking the siding off on the bottom and getting into the garage. When I took off the bottom two feet, I couldn't pick it up to put it in the trash without it falling apart. The only nice thing about it is it is tongue and groove, so it was air tight instead of spaced like I have now with plywood on the bottom two feet.
 
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