The only reason that would be a problem is if the new shake siding is thicker than the existing siding AND you need to install the new shake siding into an existing outside corner post, otherwise theres really nothing thicker J-channel cant take care of. Standard lap vinyl siding is 5/8" thick, most shake siding is also 5/8 tho. When you get into the rough spit and real deep grain stuff then it can be up to 1". Shake vinyl siding can be a bit tricky tho just to give you a heads up, going around windows/other areas that require cuts can be pretty difficult to 'lock' the pannel

My husband resided our house with vinyl shake last summer. I'll ask him to give you specifics tomorrow - he's already asleep ;-)

Meantime, here are some pictures of ours in process - maybe this will give you some info, although we not only changed from clapboard to shake but also changed color.

oops - he made a liar out of me - he's up and says typically you *could* use the same j and trim but doesn't know whay you'd want to. That's a minimal expense in the scheme of things and removing the old gives you a chance to fully inspect all your junctures for any water damage. Plus, it's easy to damage them in the tear off process so why not start fresh? I have no idea what I just typed, I am just the messenger.

{{!gwi}}

{{!gwi}}