Reforming a house can often be considerably more tedious and time-consuming than most people think. There are many talented DIYers and those with moderate to considerable experience. However, unless you have professional experience, or experience reforming a house from start to finish, you most likely lack many essentials.
Reforming a house can be relatively simple, or it can be a nightmare. The older the house is, the more of the original framing you’ll need to replace due to rot. Also, the framing of older wooden houses are often significantly out of plane — twisted, warped, bowed etc. What this means is that simply replacing the old finish with a new one is not as simple as it sounds.
Corners won’t be square, floors and ceilings won’t be level, and walls won’t be plumb or stand parallel to those they otherwise should. The good news though, is that to a certain degree, these things don’t matter all that much. The average human eye won’t be able to detect modest departures from right angles, as well as modest bowing and dipping etc.
As a rule of thumb however, walls should be plumb to within 1 millimeter per meter, and floors should be within 1 millimeter per 3 meters. It’s important that floors are relatively level, as then you can base your ceiling off of it. Also, the floor is the surface that most affect the occupants, due to frequent direct physical contact, as well as the effects it will have on stationary furniture.
For these reasons, the normal order of renovation is floors, walls, then ceiling. This of course, is generally only concerning the framing, not the actual finish layer. The order of finish layers are typically not all that important, besides doing it in such a way that minimizes the risk of damage after installation.
The Floating System
When the original framing of a house is so bad that it can’t be used as a reference point from which to base a new finish, it is usually best to incorporate the “floating” system for your floors, walls, and ceilings. This is a system that is more or less isolated from the original framing, with only minimal points of contact.
These points of contact are typically some kind of hardware that allow for a certain degree of play so as to accommodate the difference in measure between points. For floors, we have metal “jacks” whose height can be adjusted and on which large beams can be seated. However, these jacks must be firmly bonded or secured to both beam and ground or they will be pulled up by upward warping beams.
For walls, we have metal “L” brackets that come in varying sizes which are first secured to the current framing, and then to the new wall framing after it is checked for plumb. Ceilings can be based off the floor, with ties secured to the rafters spaced every meter or so in both directions. These ties are cut and placed so as to connect the ceiling framework to the rafters above.
Some have the practice of “pushing” their ceilings slightly above level at the center of the ceiling and gradually leveling out at the perimeter. This practice comes from the apparent optical illusion of a ceiling sagging due to the viewer’s angle of vision from below. This phenomenon becomes more pronounced the larger the ceiling area becomes. However, for most conventional homes, this isn’t an issue.
Also, for cases where door frames are custom-made to fit the exact predetermined height of the rooms, you wouldn’t want to push the ceiling up past this point. This however only applies to a “ceiling-first construction model”; ie, where the entire ceiling of a given floor is built first, followed by the interior walls.