# Fitting siding under window with built in j channel



## Yodaman (Mar 9, 2015)

Dixon12 said:


> How would I fit siding under this (pic)? There isn't really a room for undersill trim and also the window fin is longer than the undersill trim. So can I just fix the next course of siding with aluminum trim nails under the window? Or do I nail the undersil trim to the window nailing fin? Or just run the it under the window without fixing it with anything?



No to the trim nails. Ok to nail thru the window fin providing you: 1.) stay on the outside of the fin, no closer than the anchoring hole/slots, 2.) predrill the fin, don't want to take a chance of breaking it by driving a nail thru it.

Don't go crazy on qty, 2 or 3 tops,

Pending the width of the window and being so close to siding nail strip it might be ok to just tuck in the undersill w/o any nails. It basically acts as filler strip to support the thin slice of siding running under it.

If you are in a high wind area, I would nail it thru the fin as described.


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## carpdad (Oct 11, 2010)

Just a reminder, flashing under the trim channel that overlaps the vinyl beneath. Same flashing for the sides that overlaps the bottom flashing. A good quality stick on flashing.


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## jlhaslip (Dec 31, 2009)

It looks to me as though the window nail fins are blueskinned.


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