Identify the substrate
Bare plaster, timber, metal and masonry need products compatible with that surface. Previously painted walls in sound condition may need cleaning and preparation rather than a separate primer.
Look for problem areas
Repairs, porous patches, stains and large colour changes can create uneven absorption or show through. Use a product intended for the specific problem rather than treating one primer as universal.
Keep the systems compatible
Follow the finish-paint manufacturer’s preparation and recoat instructions. Primer coverage and drying time are separate from the finish coats entered in the paint calculation.
Practical checklist
- Spot-prime repairs only when the product system allows it.
- Do not paint over dampness or an unresolved surface defect.
