Preparing Walls Before Painting: A Complete 8 Step Checklist

Ask any professional painter what separates a long-lasting paint job from one that fails within a year, and the answer is almost always preparation. Peeling, bubbling, flaking, patchy colour and cracks that keep returning rarely come from poor paint. They come from paint applied on a surface that was dirty, damp, loose or uneven.

Preparation takes up most of the time in a good paint job, often more than the painting itself. This checklist explains each step in detail so you know what to do, why it matters and what mistakes to avoid.

Step 1: Clear the room and protect everything

Move furniture to the centre of the room or out of it, and cover what remains with plastic sheets or old cotton cloth. Cover the floor with a drop cloth, not just newspaper, because newspaper tears and soaks through. Take down curtains, switch plates, light fittings and wall hangings, and use masking tape on window frames, skirting and edges you do not want painted.

Turn off the electricity to the area when you are working near switches and sockets. A few minutes of protection saves hours of cleaning later.

Step 2: Inspect the walls properly

Walk along every wall with a torch held at a low angle. Side light shows cracks, bumps, patches and rough areas that you cannot see under normal light. Press a hand along suspicious spots to find loose or hollow-sounding plaster, and look for stains, dark patches and a powdery white salt deposit, all of which point to moisture.

Make a note of every problem before you start. A wall that is damp must be fixed at the source first, because no paint can hold on a surface that keeps getting wet from behind.

Step 3: Remove old, loose and flaking paint

Scrape away every bit of paint that is peeling, blistering or flaking, using a scraper or putty knife. Keep scraping until you reach firm, well-attached paint. For old chalky surfaces, brush off the loose powder with a stiff brush, because paint cannot grip on dust.

If the old coat is sound but glossy, you do not need to strip it. A light sanding will roughen it just enough for the new paint to bond.

Step 4: Treat damp, fungus and efflorescence

Dark green or black patches are fungus or algae. Scrub them with a stiff brush and a fungus-removing solution, rinse and let the wall dry completely. White salt deposits, called efflorescence, should be brushed off dry and then wiped with a damp cloth.

The important part is to find why the wall is damp. Check for leaking pipes, cracks in external walls, blocked drain pipes and gaps around windows. If the dampness continues, consider a waterproofing treatment before painting.

Step 5: Fill cracks, holes and uneven areas

Open up hairline cracks slightly with a scraper so the filler can go deep, then clean out the dust. Fill cracks and holes with a suitable putty or crack filler, pressing it in firmly and leaving it slightly raised. For large areas of uneven plaster, apply a thin skim coat of wall putty.

Wait until the filler is completely dry. Rushing this step is the main reason cracks and patches show through the finished paint.

Step 6: Sand until the surface is smooth

Sand the filled spots and the whole wall lightly with fine sandpaper, using a sanding block to keep the surface flat. Work in gentle circular strokes and do not press hard. The goal is a smooth surface with no ridges where the filler ends.

Wear a dust mask and keep the room ventilated. When you finish, run your hand over the wall. Anything you can feel now, you will see after painting.

Step 7: Clean off all dust, grease and dirt

Dust left from sanding is the enemy of a smooth finish. Brush the walls down, vacuum the corners and wipe with a slightly damp cloth. Kitchen walls and areas near cooking need extra attention, because oil and grease stop paint from sticking. Wash greasy patches with mild detergent water, rinse and let them dry.

Only paint on a completely dry wall. Painting over even slightly damp plaster causes bubbles and peeling.

Step 8: Apply the right primer

Primer is not an optional extra. It seals the surface, evens out how much paint the wall absorbs, improves adhesion and helps the topcoat show its true colour with fewer coats. New plaster, repaired patches, bare putty and dark old colours all need a good primer.

Use a primer that is suitable for the surface and for the paint you plan to use on top, whether interior or exterior. Let it dry fully before applying the first coat of paint.

How long should you wait between steps?

Drying times depend on temperature, humidity and thickness, so always check the instructions on the tin. As a general idea, allow filler and putty to dry completely, often a day for deep repairs, and let primer dry for several hours before painting. Apply the second coat only after the first is dry to the touch and the recoat time on the label has passed.

Good preparation might feel slow, but it protects the cost and effort you put into the paint itself. Walls prepared this way keep their look for years.