Caulking J Channel around window


Old 10-14-11, 11:13 PM
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Caulking J Channel around window

Is it necessary to caulk where the siding enters the 'J' channel around windows. I thought the 'J' channel was a water barrier itself. Is this area the cause of water leaks on the inside walls around the windows?

Last edited by the_tow_guy; 10-15-11 at 03:35 PM.
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Old 10-15-11, 08:08 AM
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Received 2 Votes on 2 Posts don't caulk inside the J. Just between the J and the window.
Old 10-15-11, 11:25 AM
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No you do not caulk it, and "no" j-channel is not a water barrier of any sort. With vinyl siding, water runs down the side j-channels and then runs BEHIND the siding at the bottom corners of a window opening. This is normal and is the way vinyl siding works. It is also the reason why you NEED to have a weather resistive barrier (WRB) like Tyvek, Typar or even felt paper behind your siding. Any water that gets behind your vinyl siding needs to shed on top of the WRB until it reaches the bottom of the siding where it will then drip out.

Some installers will install a metal flashing behind the j-channels and out on top of the row of siding that is directly below the window corners so that any water that comes down the j-channel and goes behind the siding can be directed out toward the weep holes asap.

But it is NEVER a good idea to caulk j-channels shut to try to prevent leaks. That would be a surefire way of destroying your siding if anyone ever has to work on either the window or siding in the future.
Old 10-29-11, 08:07 AM
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Building codes

Depending where you live, building codes may require you to place the "metal" above and below the window, and on any other wall openings. This metal is aluminum drip cap and can be purchased at any siding store.

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