I bought a 20 year old flat log (tongue and grover boards) home and one side of the house that gets the weather has no stain left, while the other side has a brown stain. I plan to go to a grey semi transparent stain.

1 – If I chemically strip the brown stain will the strip leak to the inside walls and cause damage?

2 – Do I need chinking or will a stain and sealant do the trick?