In most episodes, Gibbs in seen working on his boats in the basement. He gets a couple of them done, but it doesn't show how he gets them out of the basement.
Anybody know how he gets them out?
There has never been enough detail provided in the episodes that have aired to date - there are a few hints and a few jokes along the way (like knocking down a wall and using a ramp) - but this one doesn't really have an answer currently.
The boat "Diane" does have an answer as to what happened to it;
However, whether the boat was burned inside the house or not (unlikely, considering that burning a boat in a basement would probably burn the house down) is never covered in the show.