Preparing a wall before painting: steps for a perfect finish

Repainting an apartment in Paris or refreshing the walls of a house in Lyon quickly transforms the atmosphere of a living space. But the success of a painting project is not decided only at the moment of applying colour. It is beforehand, during surface preparation, that everything is determined. Surface preparation often accounts for 50 to 70 % of total work time on a painting job1. A poorly prepared wall will reveal defects, marks or premature peeling, even with premium quality paint. Here are the essential steps to achieve a sound, smooth surface ready to receive colour.

Why wall preparation is essential

The temptation to save time by skipping certain preparation steps is great. Yet this phase determines the lifespan and visual quality of the final result. A properly treated surface allows paint to adhere correctly, displays its true shade and resists daily stresses (moisture, friction, temperature variations).

In older apartments, typical of cities like Bordeaux, Marseille or Toulouse, walls often show cracks, moisture marks or layers of paint that have accumulated over decades. In a Haussmann-style Parisian apartment, the preparation phase required three days of careful work to strengthen the surface and treat all cracks before considering paint application2. These particularities require specific attention before any painting project.

Steps for preparing an interior wall

Cleaning and degreasing the surface

Before any work, the wall must be clean, dry and free of all dust, grease or dirt. Washing with lukewarm water mixed with mild detergent is sufficient in most cases. This step is particularly important in kitchens and areas near radiators, where greasy deposits accumulate over time.

Once washed, the wall must dry completely before moving to the next step. A damp surface prevents proper adhesion of filler and paint.

Filling holes and cracks

Holes left by old fixtures, cracks caused by natural building movement or plaster chips must be filled with appropriate filler. For small holes, ready-to-use filler works perfectly. For larger cracks, powder-based filler offers better mechanical resistance.

Each repair should be applied in a thin layer, then smoothed with a spatula. Once dry, the filler is sanded to create a flat surface, with no visible excess or hollows.

Sanding to level the surface

Sanding levels the filled areas, dulls the shine of old paint and creates a slightly rough surface that promotes adhesion of the new coat. Medium-grain abrasive paper (120 to 150) suits most surfaces. Sanding generates a lot of dust: it is therefore essential to protect floors and ensure good ventilation in the room.

After sanding, careful dust removal (with a vacuum then a slightly damp cloth) removes residue that could compromise primer adhesion.

Applying an appropriate primer

Primer, also called adhesion primer, evens out the surface's absorption and stabilises the base. It is essential on new plaster, on old glossy paints or on mixed surfaces. Without primer, the topcoat risks showing differences in gloss, stains or poor durability over time.

The choice of primer depends on the type of surface: acrylic primer for plaster or plasterboard walls, blocking primer for stained surfaces (nicotine, old moisture), filling primer for microporous walls. This step is often overlooked by homeowners seeking to save time or money, but it makes all the difference to the final result.

Adapting preparation according to wall condition

Not all walls are in the same state. A sound surface, already painted and in good overall condition, simply requires washing, light sanding and a primer. Conversely, a damaged wall (due to water leaks, infiltration or structural defect) requires more extensive work: stripping flaked areas, anti-moisture treatment if necessary, application of smoothing filler across the entire surface, fine sanding and reinforced primer.

In humid regions such as Brittany or Normandy, or in poorly ventilated homes, moisture can weaken walls and cause paint to peel. It is then essential to treat the cause before repainting, otherwise the defects will reappear within a few months.

When to entrust preparation to a professional

For small areas or walls in good condition, a motivated homeowner can certainly prepare the surface themselves by following the steps described. But when surfaces are large, when they show significant defects or when seeking an impeccable finish (premium matte paint, dark colour, lacquered finish), involving a professional guarantees a lasting result without rework.

On our platform, you can request quotes for your interior painting work after the professional has assessed the space, either via detailed photos and videos or during an on-site visit. Both approaches allow evaluation of the actual surface condition and proposal of a precise price, including necessary preparation. All project details (areas to treat, type of preparation, number of coats, chosen finish) are visible online by the customer, the professional and the platform, preventing misunderstandings and ensuring job security. Payment is made in two stages: 50 % at the start (to reserve the date and purchase materials) and 50 % at the end, after work verification.

What to remember before you start

Successful painting always begins with a properly prepared wall. Cleaning, filling, sanding, dust removal and primer are all steps that guarantee adhesion, uniformity and result durability. Depending on the initial surface condition, this phase may represent the bulk of work time, but it entirely determines final quality.

Before you begin, honestly evaluate the condition of your walls and the finish you wish to achieve. If you notice major cracks, damp areas or are seeking an impeccable finish, comparing several professional quotes will help you choose the tradesperson who masters preparation techniques suited to your project. A properly treated surface is the promise of a transformed living space for years to come.