Reading the Damage

A room that has been through damp or a fire looks as if it just needs a coat of paint. In practice, painting is the last and smallest part of the job. Before anything else, it's worth reading what the damage tells you: where it is, what it looks like and where it might be coming from.

Where the damage is

The position of the damage gives the first clue to its cause.

• Low on the walls, above the skirting. Bubbling paint, crumbling plasterRender (plaster)A layer of mortar (sand, cement or lime, and water) spread over brick or concrete to give a wall a straight, sound surface ready for paint or tiles. and flakesPeeling paintWhen paint loses its grip and lifts off in flakes or sheets. It is almost always a sign of a problem underneath, usually damp or poor preparation. on the floor often point to moisture from below, such as rising dampRising dampMoisture from the ground that climbs up inside walls through the pores of the materials. It shows as stains, blown render and salts at the foot of walls., or to a leaking pipe. In a shop unit, scraping showed clearly how far up the wall the damp had reached.
• Around and below windows. Water getting in at the frame or through the outside wall, or condensationCondensationMoisture in the air turning to water on cold surfaces such as windows, outside corners and ceilings. It is the most common cause of mould indoors. on cold surfaces. In an office, the paint had lifted around and below the window.
• On the ceiling. Usually water from above: a roof, a balcony, a bathroom on the floor above, or a pipe. In one apartment a whole section of ceiling plaster had come down.
• Around pipes. Behind a water heater the plaster had crumbled around the pipes, and in another home the ceiling around the water heater pipe had turned black.
• In corners, high on walls and around windows, as black spots. This is mouldMouldFungi that grow on damp surfaces, leaving black or greenish spots and a musty smell. It is a symptom of damp, not a problem with the paint., which usually points to condensation. It appears where the wall is coldest, for example at thermal bridgesThermal bridgeA spot in a building where heat and cold pass more easily than through the rest of the wall or slab, such as columns, beams and the edges of a slab..

In this flat the walls were covered in dark stains from top to bottom, and the old paint was coming away in whole sheets.

A white crust on the surface

A white crust on the wall, hard or fluffy, is saltsEfflorescence (salt deposits)A white, powdery or crystalline crust on the surface of a wall. It is salts carried by water through the masonry, left behind when the water evaporates. carried by water through the masonry. As the water evaporates, the salts stay on the surface or just behind the paint and push it off. It's a sign that water is passing through the wall, not just sitting on it.

After a fire

SootSootThe black, greasy dust that smoke leaves on walls and ceilings after a fire, or from a fireplace or stove. Paint straight over it without cleaning and priming and it comes back through. is the most visible problem, but not the only one. Heat loosens plaster and paint and can crackCrackA split or gap in render, concrete, a wall, a coating or wood. Fine cracks are usually only on the surface; ones that grow, keep reopening or run diagonally need attention. surfaces. The work after a fire has its own chapter in this guide.

The cause comes first

Scraping, plaster and a good paint job fix the surface, not the cause. If the water is coming from the roof, a leak or the ground, that has to be dealt with first or at the same time, or the damage will come back in the same place. A leaking pipe needs a plumber, a roof needs waterproofingWaterproofingThe work and materials that stop water getting through on flat roofs, balconies, bathrooms, basements, planters and tanks., and condensation needs better ventilation or insulationThermal insulationA layer of material that lets heat through only slowly, so a home keeps its warmth in winter and stays cool in summer. on the cold surfaces.

Which cause applies in a particular home can only be judged on site. Often there is more than one.