Preparing Walls for Painting

Wall preparation for painting starts with inspection

Look along each wall in daylight as well as straight at it. Mark dents, cracks, peeling, stains and uneven repairs on a simple room sketch. Check around windows, plumbing and external corners for signs of moisture. Resolve the cause of damp before covering the mark.

Identify the background: painted plasterboard, plaster, timber or wallpaper. They do not all need the same preparation. Our house painting guide helps you build a surface-by-surface scope before buying materials.

Before disturbing old paint, assess the risk of lead or other hazardous material. WorkSafe advises presuming lead-based paint on buildings from the 1980s or earlier. Get appropriate advice before sanding or scraping unknown old layers.

Protect the room and make access practical

Move small items, wall hangings and furniture away from the working area. Protect floors and fixed fittings. Agree who will move heavy furniture and deal with fixtures before work begins. Keep clear access and prevent people or pets entering active preparation areas.

Do not remove electrical fittings or introduce water around them without appropriate electrical advice and isolation. Good lighting makes defects easier to find; use the room's normal lighting as part of the final check.

Clean before sanding

Remove dust and surface contamination with a cleaning method suited to the coating. Grease and hand marks around switches or kitchens need attention because sanding can spread them across the wall. Follow the cleaner's dilution and rinsing instructions and let the wall dry.

For sound painted surfaces, start with the principles in cleaning painted walls. A wall that loses paint during gentle cleaning needs its adhesion assessed before more coating is applied.

Mould and water stains are not ordinary dirt. Investigate the moisture source and use the appropriate treatment and protective measures before decorating.

Repair and smooth the defects

Remove unsound material using a safe method suitable for the coating and wall. Fill small holes and stable defects with a compatible filler, following its depth and drying instructions. Larger damage, moving cracks or a soft wall lining may need a different repair.

Once dry, smooth the repair without leaving a ridge. Use controlled pressure and appropriate dust management. Remove the dust afterwards: a fine layer left on the wall can interfere with the next coat.

Check the wall again in side-light. A repair that feels smooth can still have an edge that shows under paint. For a large patched area, discuss whether broader surface preparation is needed to achieve a consistent appearance.

Choose sealer, primer or undercoat by the surface

See primer versus undercoat for the role of each layer. A product that works on one surface is not automatically the answer to every repair.

For new plasterboard, first confirm the stopping compound is dry and the joints are ready. Smooth the joints as specified, remove dust from the whole wall and apply a compatible wallboard sealer evenly across the face and stopped areas. Let it dry, inspect in side light and correct visible defects with the specified repair system before topcoating. Sealing a dusty wall or painting over damp stopping can compromise the finish.

How to prepare walls for painting: final checks

• The wall is dry and the source of any damp is resolved.
• Loose material and contamination have been removed.
• Repairs are dry, smooth and dust-free.
• The specified preparation coats are complete and ready for recoating.
• Flooring and adjacent finishes are protected.
• The room has suitable light, temperature and ventilation.

Choose the final paint finish with the wall's condition in mind, and leave the required drying time between stages.

Your questions