How To Clean Walls Before Painting?
QUICK ANSWER
Wash walls before painting with a TSP substitute or warm soapy water to remove dust, dirt, grease, and surface oils. Rinse with clean water and let dry completely (at least 24 hours). For kitchens and bathrooms, this step is essential. For dry rooms with intact paint, light dusting may be enough.
Cleaning walls before painting is the step DIYers most often skip and pros never skip. The dirt, dust, and especially oils on wall surfaces prevent paint from bonding properly. Even brand new paint over uncleaned walls peels within months in high-soil areas. Here is the right approach and when this step is essential versus optional.
Why clean walls before painting?
Paint bonds to surfaces, not to the dirt or grease sitting on those surfaces. Common wall contaminants: dust, kitchen grease, smoke residue, hairspray, body oils on high-touch areas like switches and door frames, mildew in bathrooms, and pet dander on lower walls. Each prevents paint from adhering to the underlying surface. Paint applied over dirty walls peels, blisters, or shows the contamination through the new color. Cleaning takes 30 minutes to an hour and prevents months of paint failure.
What is the basic cleaning method?
Sherwin-Williams recommends washing off dirt, grease, soap and oil buildup with the appropriate cleaner, then rinsing thoroughly. For most walls, mix warm water with a TSP substitute (Krud Kutter, Savogran TSP-PF) or just dish soap. Apply with a sponge or microfiber cloth. Work from bottom to top to avoid streaks. Rinse with clean water using a separate sponge. Let dry completely (24 hours minimum) before any paint application. Patch nail holes and imperfections after cleaning but before priming.
How do you handle greasy or smoky walls?
Kitchen walls and walls in homes where people have smoked need more aggressive cleaning. Use real TSP (trisodium phosphate) rather than the substitute; TSP is stronger but requires gloves and ventilation. Mix per the label (typically 1/4 cup per gallon of warm water). Wash thoroughly, rinse twice with clean water. For walls with heavy nicotine staining, apply a stain-blocking primer (Zinsser BIN shellac primer or Kilz Original) after cleaning to prevent the yellow stain from bleeding through new paint.
When should you skip cleaning?
Skip the full wash for rooms that meet all these criteria: dry rooms (bedrooms, living rooms, not kitchens or bathrooms), existing paint is intact with no visible dirt or grime, no smokers or pets with shedding fur, walls have not been touched frequently. For these rooms, a light dusting with a microfiber cloth or vacuum brush attachment is enough. Even in these clean rooms, wipe high-touch areas (around switches, doorframes) with a damp cloth before painting. The full wash is for visibly dirty or high-soil areas.
Cleaning walls before painting is fast insurance against paint failure. Use TSP substitute or dish soap with warm water for normal walls. Use real TSP for kitchens and smoky rooms. Rinse thoroughly and let dry 24 hours. The step takes 30 minutes per room and prevents the much bigger problem of repainting peeling walls a few months later. Even in clean rooms, wipe high-touch areas before painting.
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