Picture rails can help to bring down a high ceiling, and increase the apparent floor area of a room. For this reason, do think twice about their removal if you live in an old house that has them. In spite of their not being fashionable, at the time of writing at any rate, they do serve an exceedingly useful purpose by preventing nails and screws being banged into walls, so that if rearrangement of pictures or mirrors is contemplated you are not left with ugly holes.
If you wish to reduce the apparent ‘weight’ of a rail, you can disguise it to a degree by painting it the colour of the walls.
There is another reason for not removing picture rails. If the wall was plastered before the rail was first attached you can certainly take it off, make good any unevenness and holes, and nobody will be aware that it has ever been there. But, if the plastering was done after the rail was put up, or the wall was subsequently patched, there could be a slight difference in the thickness of the plaster, so that a step or a slope inwards or outwards would show.
After due consideration, you may still think that the room would be better without the rail. In that case, check for unevenness in plastering by knocking three nails through a perfectly straight batten, about a metre (3 ft) in length, so that the points of the nails protrude by precisely the same degree.
Hold the batten vertically against the wall with two nails below the picture rail and one above. If all three nails touch the surface, the wall is true. If the middle nail does not touch, the plaster above the rail is thicker; if the bottom nail does not touch then it is thinner.
Removing a rail often pulls out chunks of plaster, necessitating replastering. So find out where the fixing nails are and cut the rail on each side of them with a tenon saw. The parts in the middle will now come away and the remaining wood surrounding each nail can be splintered off with a chisel. Remove the now exposed nail with pincers or a claw hammer and do the job gently so that not too much plaster is disturbed.
The nails may be badly rusted and snap off half-way down. In that case punch the stubs well into the plaster, knife a little putty into the hole to seal off the ferrous metal and fill level with plaster or cellulose filler.If you leave the ends of broken corroded nails too near the surface, rust may bleed through whatever decorative material is subsequently applied. Should this happen, wipe off as much of the stain as you can and dab a small quantity of aluminium primer-sealer over the top before redecorating.
Sometimes the fixing nails are so covered with paint that they are difficult to locate by merely examining the surface of the wood for a slight obtrusion or depression. A small powerful magnet on the end of a piece of string, moved slowly along the wood and close to it, will be attracted to the buried metal. If this is not effective, splinter the rail along its length with a chisel, using the tool as a lever. The nails will then stand out.
In addition to showing holes, part of the plaster may come away when the rail is removed. This will have to be made good with a skim coat of fresh plaster and sanded level when dry.
You will now be faced with two types of surface, old and new, the old represented by the mature plaster of the rest of the wall and the new by your filling. These will have two different absorptive capacities, which may show as a light or dark patch under paint or may even affect wallpaper. The best method of levelling up this porosity is to line the walls or apply a coat of plaster primer all over.