How to Prepare Walls Before Painting

Here is the truth that separates professional painters from amateurs: preparation is eighty percent of the job. You can use the best paint in the world and apply it beautifully, but if the surface underneath is not properly prepared, the paint will fail. Cracks will reappear, paint will peel, and you will be repainting within two years instead of eight. This guide covers the essential steps to prepare your walls correctly before you pick up a brush.

Step 1: Clean the Surface Thoroughly

Paint does not stick to dirt, grease, mould or efflorescence. Before anything else, every surface must be properly cleaned. For exterior walls, this typically means a high-pressure wash to remove dust, algae, mould staining and any loose paint. Allow the surface to dry completely - at least 24 to 48 hours in good weather, longer if the walls are thick or porous. For interior walls, wash down with a sugar soap solution to remove grease, cooking residue and any nicotine staining. Pay particular attention to kitchen walls and areas near the ceiling where cooking grease accumulates. Skipping this step is the most common cause of premature paint failure. If you notice signs of damp coming through the walls, do not just clean and paint over it - read our guide on Damp Proofing vs Waterproofing to understand what you are dealing with before proceeding.

Step 2: Repair All Cracks and Damage

Every crack, hole and damaged area must be repaired before painting. Small hairline cracks can be filled with a flexible acrylic filler and sanded smooth once dry. Larger cracks - anything wider than a few millimetres - need to be cut out in a V-shape, filled in layers and allowed to cure properly before painting. Structural cracks that reappear need professional attention before painting. On exterior walls, pay special attention to cracks around window and door frames where water can penetrate. For badly damaged or crumbling plaster, consider having the affected areas replastered entirely before painting. Our article on How to Fix Peeling Paint covers what to do when the paint itself is the problem and needs to be removed before repairs.

Step 3: Sand and Create a Key

Any glossy or semi-glossy surfaces need to be sanded down before repainting. Paint does not bond well to a shiny surface. Use medium-grit sandpaper (80-120 grit) to dull the sheen and create a mechanical key for the new paint to grip. This applies to previously painted gloss enamel trim, kitchen cabinets, bathroom tiles and any other shiny surface. After sanding, wipe down with a damp cloth to remove all dust. Allow to dry completely. For exterior textured surfaces that have chalked badly, you may need to use a bonding liquid primer rather than simply sanding to re-establish adhesion.

Step 4: Apply the Correct Primer

Primer is not optional - it is the foundation of your paint system. Different surfaces need different primers. New plaster needs an alkali-resistant primer to prevent the alkalinity of the cement from attacking the paint. Bare wood needs a wood sealer. Metal needs a rust-inhibiting primer. Stained walls - particularly those with water stains or nicotine - need a stain-blocking primer to prevent bleed-through. Using the right primer ensures your topcoat goes on smoothly, covers evenly and bonds properly. Many professional painters will tell you that the primer coat is more important than the topcoat. In hot Cape summers, apply primer in cooler morning temperatures for best results - see our guide on Tips for Painting in the Cape Summer for more on timing your application.

Step 5: Protect What You Are Not Painting

Mask off all surfaces you do not want paint on - window glass, door handles, light switches, skirting boards, ceiling edges. Use quality masking tape and apply it carefully for clean, sharp edges. Cover floors, furniture and fixtures with drop cloths. Good masking takes time but saves enormous time at the end. It is far easier to apply tape neatly before you start than to clean dried paint off glass or floor tiles afterwards. Choosing the right paint to apply over all this preparation is the final step - our guide to Interior vs Exterior Paint will help you make the right choice for each surface.

Franschhoek Painters never cuts corners on preparation. Every job is properly cleaned, repaired and primed before a drop of topcoat goes on - because we want your paint job to still look great in ten years.