Return to the Windows Forum | Post a Follow-Up

Water-tight without the J-Channel

Posted by embedded_tim (My Page) on
Sun, Oct 23, 11 at 11:58

Hi Guys-

Another question for all you pro's...

I've done a fair amount of googling on this one... any recommendations on how to apply exterior trim to new construction casement windows that avoids the unsightliness of running vinyl J-channel all around the window?

I'm not a brake pro, so bending metal isn't that great of an option for me (never understood how mitering alum around a window made it leak-resistant). I have talked to an Azek rep and he offered me the rabbeted 1by trim board. It certainly looks beautiful, but its not a full j-channel (nothing returning underneath the siding). Can you put normal vinyl j-channel pieces underneath the rabbet to create a leak-resistant barrier? If not, what other methods can be used to: 1. make the window look nice 2. not leak like a sieve.

Finally, anyone have any recommendations outside of exposed j-channel or rabbeted board? I'm always looking for better ideas...

Thanks in advance!!

Follow-Up Postings:

RE: Water-tight without the J-Channel

Vinyl siding as a system is not as water resistant as a wood siding system, as gaps must be left for expansion/contraction. Traditional J is no true waterproof joint. That's why the "rain screen" concept has been adapted for synthetic siding systems.

The miter is just cut on the header casing piece, the verticals are cut square at full length and run up under the cap; there's your waterproof "miter" joint.

RE: Water-tight without the J-Channel

There are windows that have the option of a nailing flange and you can get a clip in J-Channel or sill expander that can be made to act as a J-channel.

If you run a flat trim, you should put a drip edge above the window and above the trim.

You will need some sort of j-channel to cover the cut edges on the siding regardless.

The integrated look is a bit better.

RE: Water-tight without the J-Channel

No siding system is intended to be the final drainage plane on a house.

The siding is there to protect the actual drainage plane from damage mechanically and from the sun.

Tar paper used to be the drainage plane of choice, but there are plenty of newer materials available.

Though sometimes I have my doubts what the new materials will look like in 60-70-80 years.

RE: Water-tight without the J-Channel

Ya, I noticed the snap on trim with built-in J-Channel for the Andersen 400 series. Unfortunately they appear to cost a large amount of $.

So in terms of a casement window, does this sound like proper steps for a good Weather Resistant barrier:

1. Tyvek wrapped / stapled / taped into the window opening
2. Flexwrap the bottom and lower sides of the opening
3. Silicon caulk around the nailing flange
4. Nail in the windows
5. Flash tape the sides
6. Flash tape the top

What do people recommend doing to the window after step 6? I'd like to avoid running straight vinyl j-channel. Any ideas on the azek board? I'm looking for a nice look, but also don't want water easily running under the vinyl siding.

Thanks again!

RE: Water-tight without the J-Channel

3. Not a fan of silicon in this application as compared to some other sealants but check the compatibility with the flashing tape manufacturer.

Easy finish trim would be an foam PVC board that could be run or routed for a j-groove. I would bend up an L-piece of coil to go against the wall to provide the proper drainage to outside the siding.

 o Post a Follow-Up

Please Note: Only registered members are able to post messages to this forum.

    If you are a member, please log in.

    If you aren't yet a member, join now!

Return to the Windows Forum

Information about Posting

  • You must be logged in to post a message. Once you are logged in, a posting window will appear at the bottom of the messages. If you are not a member, please register for an account.
  • Please review our Rules of Play before posting.
  • Posting is a two-step process. Once you have composed your message, you will be taken to the preview page. You will then have a chance to review your post, make changes and upload photos.
  • After posting your message, you may need to refresh the forum page in order to see it.
  • Before posting copyrighted material, please read about Copyright and Fair Use.
  • We have a strict no-advertising policy!
  • If you would like to practice posting or uploading photos, please visit our Test forum.
  • If you need assistance, please Contact Us and we will be happy to help.

Learn more about in-text links on this page here