And you may find yourself
living in a shotgun shack...
The term may also be shotgun double. It's used to describe a sort of house. They are two dwellings built side by side as one building and divided along the middle into two apartments. There are usually two front doors, one of each side, and maybe one window each between them, depending on how wide the front is. These buildings are among the most common in New Orleans and in many other cities and small rural towns as well.
Normally, the rooms run in this order: front room, bedrooms, bathroom, kitchen in the very back. If the lot allows it, there is often a shared courtyard in the back that is usually also fenced up on each side. To get to any one room, you have to go through all the other rooms, as there are typically only two forms of entry and exit, the front door and the rear door running to the courtyard.
They are referred as "shotguns" because each side it built as one long rectangle, with all the doors built along the outside wall. The theory is, that if all doors are open inside, you can fire a shotgun in through the front door and it would go the entire length of the apartment, with nothing in its way, a straight shot. I am not sure why this term was applied. Perhaps it addressed the easy access you could make if you wanted to rob the place, or that it did not provide protection if you came under fire while inside.
In New Orleans, shotgun doubles can be the cheapest affordable housing for the square footage (because they cannot really be cut up any smaller than along the middle without costing the owner extra for relocating the ancient plumbing), but they can also be re-united into one dwelling, since they are often made and un-made depending on need. You want a shotgun double, just wall in the large front rooms; you want one dwelling, just knock the walls in. If a house began as a shotgun double, fireplaces usually frame the inside walls, so that if you want to make it one dwelling after the fact, you have to leave the fireplaces standing freely, a sort of mirrored wall in the center of a now open room.
These buildings will be usually propped up off the ground for flood prevention and typically have attic spaces high enough to convert into second floor living space if needed. Many of the most well-restored buildings look on the outside to be nothing but a simple squat structure, but when you inside, it can be opened up as high as the outside roof allows, and besides, the ceilings are already going to be high, as they helped to release heat in the summer.
Go here for a little more info: http://www.greatbuildings.com/buildings/Shotgun_House.html