What problems are you likely to come across with the internal walls of a Georgian, Victorian or Edwardian period house? Typically you will find wallpapers and Artex coatings to be removed, loose or cracked plaster, areas of missing plaster and stains and mould.
A common problem is walls which have been covered with Artex or other textured plasters, or woodchip papers.
In most old houses, large areas of original plaster are 'live', particularly at the level of chairbacks and below. If you knock on a wall in several places you will find that it sounds hollow. There are usually three coats; the first 'render' coat may have lost its key to the bricks or laths, or the second 'floating' coat or third 'setting' coat may have separated. You can often live with this; as long as you strip wallpaper carefully it should not fall off the wall.
Fine cracks can be caused by shrinkage, or be evidence of live plaster. Large cracks can be the result of minor settlement and heave. For example, a crack may open and close over the course of a year as the ground under the house dries and moistens.
Where flawed plaster has been mishandled, it can fall off the ceiling or wall. Plaster mouldings can be re-fixed. Areas of flat plaster are best patched.
Stains commonly arise from cigarette and pipe smoking. Sugar soap will remove this before redecoration. Staining also occurs if a chimneybreast has become damp; the moisture washes oils from the soot to the surface.
Mould occurs because of damp. You need to determine the type of mould and the cause.
If plaster becomes stained due to damp or mould, any paint or paper applied over it tends to stain subsequently.