What your walls are made of
Most American homes built since the mid-twentieth century have walls and ceilings of drywall (gypsum board): panels of gypsum plaster faced with paper, screwed or nailed to wood or metal framing. The seams are covered with paper or mesh tape and joint compound, sanded smooth, primed and painted. Older homes often have plaster over wood lath, which is harder, heavier and repaired differently. Knowing which you have matters before you cut, patch or sand anything; tap the wall and look at an outlet’s edge, where you can often see the layers.
Paint is the finish layer. It protects the surface and makes it washable, but it also shows every problem underneath it. Peeling, bubbling, cracking and stains are almost always symptoms of moisture, poor surface preparation, or movement in the structure, not of bad paint alone.
Before you sand or scrape: older homes
Two hazards make preparation in older homes different.
- Lead-based paint. The EPA notes that homes built before 1978 are more likely to have lead-based paint, and that dust and chips from deteriorating lead paint are one of the most common sources of lead exposure in homes. Any renovation, repair or painting in a pre-1978 home that has lead-based paint can easily create dangerous lead dust. Contractors paid to disturb painted surfaces in these homes must follow the EPA’s Renovation, Repair and Painting rule.
- Asbestos. The EPA lists textured paint and patching compounds used on walls and ceilings among products that may contain asbestos. You generally cannot tell by looking, and material in good condition that will not be disturbed should be left alone. Before sanding or scraping old textured ceilings or walls, have the material tested by an accredited professional.
Moisture comes first
Many wall and ceiling problems, from water stains to mold to peeling paint, start with water. The EPA puts it simply: the key to mold control is moisture control. Fix the leak and dry the area, ideally within 24 to 48 hours, before repairing or repainting.
What homeowners can usually handle
Patching small and medium drywall holes, fixing cracks and nail pops, caulking tubs and trim, removing wallpaper, sealing and repainting stained ceilings once the leak is fixed, and repainting rooms are all approachable projects with the right preparation.
When to bring in a professional
Large or recurring cracks that suggest structural movement, mold over more than about 10 square feet (the EPA’s threshold for considering professional help), water damage from sewage, suspected asbestos, and disturbing paint in pre-1978 homes where lead has not been ruled out all call for specialists.
How our wall and paint guides work
Each guide starts by identifying why the problem happened, because patching or painting over an unaddressed cause brings the problem back. Then it walks through the repair with the materials listed, and flags the points where testing or a professional is the right call.