Preparing a wall for lining: what a liner can and can't hide

Lining paper is often sold as the cure for a poor wall, and it does hide a lot: fine crazing, patchy porosity, the ghost lines left after old paper is stripped, the slight colour differences between old plaster and new filler. What it cannot do is defy physics. A liner is a thin, flexible skin. It will follow the shape of whatever is behind it, so a hollow, a proud lump, or a live crack that is still moving will all read through the finished surface. Good preparation is what turns a liner from a cosmetic cover into a durable base.

Filling comes first. Hairline cracks and small holes are filled and sanded flush, because a liner bridges a gap but does not fill it, and an unfilled dent stays a dent under the paper. Cracks that reopen season to season are structural movement, not surface damage, and paper will tear along them no matter the grade; those need the cause addressed before any decorating starts.

New or bare plaster needs time and then sealing. Fresh plaster holds building moisture for weeks and should be allowed to dry out fully before anything is hung, or trapped damp will push the paper off later. Once dry, bare plaster is still thirsty and will suck the water out of paste far too fast, so the paper grabs before it can be positioned and the bond is starved and weak. A coat of size, a practice old enough that it was once done with animal-glue solution, evens out the wall's absorbency and gives the paper a few seconds of slide to be brushed into place. Size also makes the eventual removal cleaner, because it stops paste bonding directly into the plaster.

Old gloss or a shiny previous finish is the opposite problem: paste cannot key to a slick surface. Those areas are keyed by sanding to a dull matte and then sized. Powdery or flaking distemper has to come off entirely, because no liner will hold onto a layer that is itself letting go of the wall. Spend the time here and the liner does its real job, which is to give the finish covering one clean, sound, uniformly absorbent surface to sit on.