Tried to convert Firehouse Garden to a Greenhouse and left with disappointment

I don't know if this is a me problem or a current game limitation

Converted the privacy fence to a brick wall, doors to metal doors, roofing I was having difficult with and resorted to building Small Metal Support to place roofing as the option to roof was not showing when I was trying to place it between a corner to get the "Must be supported on at least two sides" annotation with supports in place and without - probably not fully understanding how roofing works, but the sky light frames didn't give me any issues.

Completed the roofing to my knowledge, placed a large heater and it was not heating the room.

I am not sure if I haven't placed the roofing correctly, there is currently limitation with game in regards to building extensions or some reason I am not aware of