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Learn2Build 05-28-2010 12:06 PM

Help! Casings around window with integrated J channel?
Hi all! I am new to the forums and would appreciate some ideas from others who have ran into a similiar situation.
I have installed vinyl windows with an integrated J channel with every intention of installing Craneboard7 vinyl siding, but afterwards (windows already installed) I decided to go with HardiPlank 8 1/4" Lap siding. I don't want to butt the HardiPlank into the J channel due to possible water getting behind the siding. I am using 5/4 LP Smart Trim board for my siding corners, and would like to use them as for window casings.

My question is if I should router outer the edge of the trim board so it fits into the J channel and caulk that?
Would it be better to butt the trim up against the window frame, which is what I seem to gather from some other threads? That way the trim would be at outermost edge covering up the J channel.
If I do this will a 3/16" gap between the window and casing sufficient for caulking?
Any suggestions for the best caulk for between the vinyl and painted casings?

I have seen a couple old threads on this same issue, but can't seem to find I a real good answer how anyone completed theirs, or how it has held up over the years. I am going to try and nail it out this weekend so everyone's suggestions are highly appreciated. Thanks to everyone in advance.

white29 05-31-2010 07:24 AM

Hi Learn2, I'm the starter of the original thread on this a few years ago. Here's what I did and I've been very happy with the results: 1). I flashed over the windows nailing fin with this stuff; 2).I used #2 pine 1x4's (3/4" actual) primed and butted up to the window frame,under the Integrated channel. I caulked all joints . 3).I had a siding guy wrap all the casings in aluminum. 4). I caulked where the casings met the window channel and on the outer edge where the Hardiplank met the casings later on after the siding was up. Oh, I also installed a drip edge at the top of each window prior to siding. As far as caulk goes spend the extra and get decent stuff. I think I used a GE or maybe Dupont silicone. I did not use paint but a solid color stain(Flood) on the siding. Also, Azek PVC could be used to trim your windows instead of wrapped pine if you are concerned about water. I really couldn't be any happier with how my project turned out and I'll try to post pics as time allows. :thumbsup:

Scuba_Dave 05-31-2010 09:00 AM

I do have 3 windows with the integrated J channel
I did install the Hardi up to the window for those 3
I did not have to route anything for the Hardi to fit into the channel

kwikfishron 05-31-2010 09:31 AM

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You want that channel of the window completely covered by trim.

I’d be using 2x trim not 5/4 so the trim comes out past the window giving you a place to caulk the trim to the window and not trying to fill what’s left of the channel gap.

white29 05-31-2010 10:56 AM

Kwickfish, HUH?

kwikfishron 05-31-2010 06:44 PM

199 Attachment(s)
OP says he has windows with the J-channel built in for Vinyl Siding and now wants to install Hardi and is concerned because you can’t get into the channel to properly caulk.

His solution is to trim the window and butt the siding to the trim so it can be properly caulked, that’s great.

My concern is that the 5/4 trim he wants to use is only 1” thick. OP says (if I’m understanding correctly) that still leaves him with 3/16” gap showing in the channel and is that acceptable to caulk.

What I’m saying is no. Rather than trying to caulk the 3/16” gap of the channel (and wasting a lot of caulk as the cavern try’s to fill up) the thing to do is install thicker window trim (1 ”) so it completely caps the channel and then now stands proud of the window ”+. Now the channel of the window is capped and you can caulk the trim to the face of the window and the siding to the trim.

I personally don’t like 5/4 trim for new windows. Most new construction windows protrude 1 ” out from the nail flange and after installing "30lb ASTM Felt, blind caulked" (or whatever you choose) over the flange the 5/4 trim the trim comes out flush to the face of the window leaving no acceptable offset for a proper caulking job. 5/4 for corners, OK.

All of that said, OP said he originally was going with Vinyl Siding when ordering the windows and then after the windows were in decided to go with Hardi. If he had stayed to the original plan and go with Vinyl Siding what would keep the water from getting behind it?

Learn2Build 06-01-2010 02:14 PM

Agreed, I would prefer to trim the windows versus sliding the Hardi into the j channel. Sliding the trim into j channel isn't an option since the j channel is only 1/2" wide which would leave the lap on the hardi sticking out further than the trim. When I tried to butt the 5/4 trim against the window the window was sticking out about 1/16 " further than than trim. It was enough to cover up the J channel allowing for adequate caulking.
I would prefer the look of the window being recessed in the trim, but do you all think it would look odd if the 5/4 trim at the corners sat closer to the hardi than the 2x trim around the windows?

kwikfishron 06-01-2010 02:46 PM

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Unless the customer tells me otherwise I always use 2x over 5/4 every ware. It just looks better, adds depth and more detail. Not to mention a better caulking surface, especially on windows.

Learn2Build 06-01-2010 05:10 PM

Unfortunately, I have the 5/4 trim up on almost all of my corners :eek:.
I don't how much a 1/2" of difference would make on the aesthetics from the 2x trim around windows vs. the 5/4 trim everywhere else.

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