Sealing vinyl siding

Hey everyone, just a quick question on if there are any situations where vinyl siding should be sealed. I know that the seams and J-channels should not of course, to allow movement. I believe the gap between the siding and brick veneer in the photo should. My question is about the gaps around penetrations such as the outlet housing and hose bib? It seems like these would be easy places for moisture intrusion but then of course there’s the concern about allowing movement. Call this out or no?

Thanks, Ed

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Here is some good info. There is an installation guide. I use these types of guides for vinyl, cement fiber, engineered wood etc. to help me understand good building practices.


I agree with Brian. This is the same document I reference in my inspections.

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Curious, have you ever bothered to look at the bottom edges of most vinyl and metal sidings??

Now why do you think that is???

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Even if installed correctly, vinyl siding is not waterproof.


As Larry said, Vinyl siding is not weatherproof, and thus the importance of the Weather barrier under the siding. If the WRB was not installed properly, you will get leakage.

“Vinyl siding has always been designed as an exterior cladding, not a weather resistant barrier. Vinyl siding is designed to allow the material underneath it to breathe; therefore, it is not a weather tight covering…. To achieve designed performance, vinyl siding must be installed over a weather-resistant barrier system that includes 1) a continuous weather resistant material and 2) properly integrated flashing around all penetrations and where vinyl siding interfaces other building products such as brick, stone, or stucco” [3] (emphasis added).


Thank you Brian, that looks like a great resource!

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That’s a great point Jeffrey, thanks!

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Thanks everyone for your responses. Much appreciated!

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Since IRC 2006 weather resistant barrier has been required under vinyl siding.

Here is a photo of what can happen without the Tyvek.


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That can still happen with Tyvek if the siding is not properly installed. Tricks of the trade.


Here is a vinyl siding installation trick, Install flashing under the J channel and then on top of the upcoming siding panel. Water will run down the J channel, on top of the flashing, then on top of the nailing flange, the water will run out through the weep holes in the bottom of the siding. Most builders don’t know this or do not do this. :nerd_face:
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I used to install a section of flashing that came out onto the brick with about 1/2" profile so that it could be caulked to the brick and to the jchan. Water running downward has an opportunity, thanks to cohesion, to wick up behind the jchan. While there should be a weather resistant wrap, it can still cause issues over time. Loosening, rusty nails, little rot spots, etc…

I write it up as missing flashing/caulking. If nothing else is prev. main. and helpful.

That’s an awful install job on those windows! When we’d come across a hack job like that I’d tell the fella that I worked with that it looked like him and his brother were there before. Hehe…

Did you figure out the same trick for v-siding installed vertically? :thinking:

Yep, sure did, but I will keep that to myself. Don’t need to debate it.


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yep…that’s the way it should be done…Around here builders spend a lot of time flashing the top right but leave the bottom out of the equation…I guess they figure house wrap will help drain the water. If they gave the framer some vinyl flashing they could nail it up before they set the windows.