When the home was originally designed, one of the designs called for an additional 3 x 15 foot extension.
When the home was built, the room extension was not incorporated therein.
Basement is fully finished with no visible access to this extension from the basement.
A deck was then constructed over the area, deck framing is boxed in beneath so there is no visible access to really determine how, and/or why this was done.
It looks really strange…