window/j channel /siding question

raypunzel · 05-01-2008, 07:15 AM

Hello all,
This is my first post and sorry to say it is for help. I am replacing an octagonal window and have a question regarding the siding butting up to the j channel that borders the window. How does one prevent moisture from getting behing the j channel where the channel accepts the siding? I realize that silicone caulk should be used where the window meets the j channel but what about the siding butting up to the j channel, how do I make sure that any water around the window is diverted correctly away from FROM getting behind the siding?

Big Al · 05-01-2008, 08:26 PM

We didn't have fancy smanshy vinyl clad octagon windows with built in drip caps in my day. We had wood windows and we liked it ... we loved it ! I used to install vinyl or metal drip cap on 3 sides,J-channel all around and side. In 30 years I've done 100's. Never used caulk. If it makes you comfortable use it. Siding is designed to breath. Make sure your tyvek is tight and taped then any water that gets thru won't damage anythind.

glennjanie · 05-02-2008, 01:35 PM

Welcome Raypunzel:
Hey, help is what we are here for. It thrills me to see a question that I have dealt with in my years; then I can help someone.
I would cut the octagon pieces with an 11* miter on each end of the face part and back part, cut the bottom of the channel an inch or so longer so that each one can overlap the one below it. Then caulk the J before installing the siding. Think of roof shingles, each one has to overlap the one below it or the water would be funneled in.
Glenn

tinner666 · 05-06-2008, 04:48 PM

http://www.rooferscoffeeshop.com/show_album_photo.asp?userid=30&AlbumID=313&file=37 02&s=0