It does not drain water off the top of the window but to both sides where some it will end up behind the siding when leaving the bottom of the side j s it s a built in fault with regular and integral j s and the way 99 of people install vinyl and similar sidings.
Installing vinyl siding around windows with integrated j channel.
The vinyl siding trim pieces should slide back and forth slightly.
Continue installing courses of siding along the sides of the window leaving 1 4 inch spaces within the j channel at the end of each piece of the siding for expansion.
Through the middle of the slots.
Alternatively i use vinyl window and door casing which is essentially a 2 1 2 in.
Caulk behind the vinyl nailing flange of the window first then install grace strips over the flange and then you can run your siding right into the window j channel.
Some modern vinyl windows however incorporate a j channel right into the.
For the window first position the j channel against the window casing.
Position the j channel under the window.
Cut and position an undersill trim if necessary see when to use undersill trim.
Mark cut and notch the top.
Nail it to the wall but remember not to nail it tightly.
Another option is crane board makes an adapter that snaps onto the windows built in j channel that turns it into a 1 1 4 deep j pocket for use with their insulated siding.
Drive roofing nails every 8 to 10 in.
The intergral j is a real bad idea.
Windows and doors install the j channel vinyl siding around all four sides of a window or three sides of a door.
No pieces to separate.
When i know a house will be sided in vinyl i select windows that have either an integral j channel or a slot to receive an applied cap that creates a receiver channel.
Traditionally j channel was a siding trim molding fastened around windows and doors which then received the siding.
On the top of the window don t run it to tight leave room for the water to run off.
Integral j is fine its actually better.
Install j channel under the window.