A:
Dear Disturber of the Force,
I am much afraid that if you were to reverse the effect of gravity for the entire earth, not only would your buildings be pushed away from the earth's core roughly at a diminishing 9.81m/s^2, but the mantle and core would be repelled at even a faster rate, causing no end of chaos. I think your houses are toast. And no amount of scraping will remove the black parts.
If you are willing to scale back on your wanton destruction and simply dangle the house by its foundation, we might be able to get things together enough to ... watch... them... fall apart.
Well, to answer this fully, I thought: we are going to need a step-by-step breakdown of how a house is built to determine its upside-down-hold-together-atude-ness. So, I built a house. As it turns out, it was too windy on Monday to fly the trusses, and we didn't work on Sunday, so it ended up taking about 140 hours to build. Sorry for the delay, register your complaints with the wind.
As it turns out, a well built home will hold up astonishingly well against vertical forces. While the foundation was being poured we placed J-shaped straps of metal (known as hurricane straps) at the corners of the building. <Img src="http://theboard.byu.edu/filelib/Images/47556%20bolts.jpg"> Every two to three feet we left an eight inch long 1/2 inch diameter anchor bolt embedded into the foundation. To these we bolted 2x6x12 pressure treated "greenboards" with a sealant under them and square plate compression washers (for some reason the square washers withstand over 1000lbs more force than round ones).

And all that is just on the outer walls, the pony walls you can see going up in the last picture were adhered by a sub-floor adhesive and then nailed with a .27 caliber powder actuated nail gun (which was WAY cool btw...).
To sum up, those beams aren't coming free of the foundation. The next joint would be the weakest to a vertical force in my opinion. Most of the nails attaching the walls to the greenboards were driven vertically in, thus are not much good for holding against being pulled right back out when the house is flipped. You can't just write them off, however, and a great many were toenailed (angled) in. In addition the sheeting that covers the outside walls was heavily nailed to the greenboards, as those would be running perpendicular to the new gravitational force, they would have to shear (not likely) or split the sheeting (even less likely if the wood is still good) before failing. Most likely would be the walls bowing until the nails were bent "down" towards the g force. I find this scenario difficult to imagine as well, but timber is
heavy, there would be a lot of strain in a direction not planned for. (No pictures here, turns out any pic close enough to show detail ends up showing little more than the head of a nail embedded into wood... sigh.)
Walls are pretty much symmetrical, so we'll move on to the last major joint: the trusses. As I said, Monday was too windy to fly the trusses, and I was laminating a 6x10x32 beam for much of the time they were able to actually get them in, so no pictures here either. (Which is a shame, really, the 100ft crane was something to see.) Roofing has notably different specs depending on the state you are in and the building code of your particular area. In areas with high chances of major storms or earthquakes, you might find hurricane straps around each joint, and even up and over the rafters in some cases. A 200 mph wind can create some major forces, and a building built to withstand something along those lines is much more likely to hold up in your topsy-turvy condition. Ours didn't have to meet that strict of code, and while the entire roof was toenailed, I don't know how well it would hold if the straps failed.
Well, there you have it, Señor Sith-Lord, I figure you've already got housing all taken care of, so I took the liberty of giving your house to someone else. The Jackmans sure are looking forward to moving in.
Cut out doors and windows in order to make a room.
Adapt the nothing therein to the purpose in hand, and you will have the use of the room.
Thus what we gain is Something, yet it is by virtue of Nothing that this can be put to use.(XI,5-7)-Tao