Why preparing walls before painting matters
The best results start long before the first coat goes on. Skipping proper prep can lead to cracks showing through, paint that won’t adhere, or dark patches that bleed through the top coat. Properly preparing walls makes it easier for your chosen paint colour to cover evenly and requires fewer coats.
Proper preparation:
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Helps paint stick better to the surface
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Reduces the risk of bubbling or flaking
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Creates a smoother finish with better coverage
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Extends the life of your paint on interior walls
Once major cracks or damage are repaired, the rest of the wall surface can be addressed with a basecoat or filler to ensure a uniform finish.
Assessing the wall condition
Before you start painting, take time to thoroughly assess all the walls in your room. Look closely for any peeling paint, cracks, or holes that need to be filled before you can achieve a professional finish. Pay special attention to areas that may have been affected by dampness or water damage, as these can affect how well your chosen paint adheres to the surface. Run your hand over the walls to check for any rough patches or uneven finish that could show through your new interior paint. Make a note of the chosen paint colour and the type of interior paint you plan to use, as this can influence how you prepare the walls for painting. By carefully inspecting every wall and identifying any issues early, you’ll ensure your surfaces are properly prepared and ready for a flawless coat of paint.
Preparing your room for painting
Clear enough space to move safely around the room and complete the prep work without disturbing dust sheets or tools. Wash dirty areas with warm soapy water, rinse where required and allow the walls to dry.
Repair and sand each surface properly to create a smooth surface before applying primer or paint. Careful preparation supports a fine finish and helps each coat cover consistently, reducing the risk of needing several coats to correct visible marks or uneven absorption.
Clear and protect the room
Move furniture away from all the walls and remove pictures, curtains and loose fittings. Cover remaining furniture and the floor with dust sheets before sanding, washing or painting. Mask fixed edges where required, provide adequate ventilation and follow every product’s safety instructions.
Inspect the walls before painting
Use a bright light across the surface to reveal cracks, holes, stains, flaking areas and other imperfections. Identify damp, mould or recurring dark patches before applying new paint, because decorating over an unresolved moisture problem will not provide a lasting repair.
Remove wallpaper and adhesive
Remove wallpaper rather than applying paint directly over loose or damaged coverings. Use a stripping knife carefully to avoid gouging the plaster. Once the wallpaper is removed, wipe away adhesive with a damp sponge and clean water, then let the walls dry completely.
Remove loose and peeling paint
Scrape away peeling paint and any old paint that no longer bonds to the wall. Feather the edges of sound existing paint with sandpaper. Older coatings may contain hazardous substances, so seek professional advice before sanding when their age or composition is unknown.
Clean walls before painting
Clean walls to remove dust, dirt, grease and grime. Warm water with a compatible cleaner may suit light contamination, while kitchens may need a degreaser. Sugar soap can help with decorating residue, but rinse as directed so it does not affect adhesion.
Treat mould, mildew and algae
Do not cover mould with a fresh coat. Address the source of moisture or poor ventilation before using a suitable fungicidal treatment. Centrecoat GS36 Fungicidal Wash is listed by Promain for removing mould, algae and mildew before paint application.
Fill holes and surface damage
Remove loose edges and dust before using a filling knife or putty knife to fill holes. Press compatible filler into the repair and finish slightly proud where sanding is required. Deep holes may need several applications, depending on the product’s permitted depth.
Repair cracks in plaster
Check whether cracks are stable before filling. Repeated or widening cracks may need investigation beyond routine wall prep. For minor stable cracks, remove loose plaster and fill the gap. Flexible joints may require an acrylic jointing compound rather than rigid filler.
Allow filler to dry completely
Filler must dry completely before it is sanded, primed or painted. Drying depends on product, depth, temperature and ventilation, so a firm outer surface may hide damp material. Check for shrinkage, pinholes or low spots and repair them if required.
Sand walls smoothly
Sand walls after repairs to remove filler ridges, rough paint edges and imperfections. Use fine sandpaper for final smoothing and lightly sand a gloss finish where the coating system requires a key. Avoid damaging plaster or creating unnecessary dust.
Remove remaining dust
Use a vacuum cleaner to remove dust from the room, floor, skirting and walls. Complete a final clean with a damp cloth or sponge where appropriate. Remaining dust can reduce paint adhesion and create a gritty rather than smooth finish.
Prepare new plaster
New plaster must dry until it is uniformly pale and free from dark patches. Do not rely on a fixed waiting time. Once the walls dry, remove surface dust and follow the chosen paint manufacturer’s preparation instructions.
Apply a mist coat where specified
A mist coat is diluted water-based paint used on suitable new plaster. Use only a product that permits this application and follow its dilution ratio. Apply the mist coat evenly and let it dry fully before the first coat of chosen paint.
Do not use PVA as a general primer
PVA should not replace a specified wall primer or mist coat before normal painting. It can form a sealed film that prevents some paints bonding correctly. Use the preparation system recommended by the plaster and paint manufacturers instead.
Painting your interior walls
Once the surface is ready, apply the paint using a quality brush or paint roller. Always start from the top and work down. Two coats are usually enough, but prepping properly helps avoid needing extra layers.
For best results, paint windows in the morning to allow them to dry properly, and pay special attention to painting around windows for a neat, professional finish.
Start with your mist coat if you’re painting over new plaster. Then apply your first coat of your chosen paint. Let it dry as recommended before applying the second. Allow each coat to dry fully between applications for the best finish.
Prime porous and repaired areas
Primer helps paint bond to porous plaster, sealed stains and filled repairs. It can reduce uneven absorption that makes patches visible through the top coat. Choose a product compatible with the filler, existing paint and intended finish.
Prepare glossy existing paint
Clean and remove grease from glossy paint, then lightly sand where the new coating requires abrasion. Wipe off all remaining dust. A bonding primer may be necessary when changing the gloss finish or when paint adhesion is uncertain.
Mask edges and protect fittings
Apply masking tape to clean, dry edges around skirting, trim and fittings. Cover sockets and switches safely rather than brushing around dirt. Careful masking protects the room for painting and helps produce clean lines around ceilings and woodwork.
Complete the final surface check
Inspect walls from several angles in strong light. Feel across repairs and check corners, gaps and edges. If another defect appears, fill, dry, sand and clean it before priming. The surface should be sound, smooth, clean and dry.
Prepare walls for the first coat
Stir the primer or paint and apply it with the recommended brush or roller. Maintain an even film and never overload repaired areas to disguise poor preparation. Allow the first coat to dry for the stated time before applying the next coat.
Wall preparation products from Promain Paints
Promain’s range includes fungicidal washes, treatments, fillers and products for preparing walls for painting. Centrecoat GS36 Fungicidal Wash supports pre-paint cleaning where biological growth is present, while suitable repair products can address cracks, holes and flexible gaps.
Shop wall preparation products
Shop wall preparation products for interior walls, exterior walls and professional projects through Promain. For advice, call 01462 421 333. The technical team can help you prepare walls for painting and match each treatment and primer to the chosen paint system.