Ask any of our interior painters Brisbane team what the secret of a perfect finish is, and they would not tell you that it is costly paint, or fancy rollers, or even years of practice. They would all give you the same answer: Preparation. One critical thing that stands between you and that professional finish is the cleaning of the walls before being painted. However, in many real job situations, wall cleaning is done only when it is needed (for example, grease, mould, or heavy staining).
At Painting by MOLI, we know that we do not do things the easy way, but the right way. We have already witnessed numerous DIY tragedies, in which not using the scrub resulted in flaking paint, blistering surfaces, and squandered money. So here we are spilling our trade secrets, cleaning before painting walls, answering the most common questions, do walls need to be clean before they are painted, and elaborating on the top 5 tips of cleaning before a painting job that will ensure you get that dream finish.
The Great Controversy: Do You Have to Wash Walls Before You Paint?
The elephant in the room is often left unaddressed. Do you have to clean before getting your walls painted?
The short answer is: Yes. The long answer involves understanding why paint fails. Modern paint technology is incredible, but it is designed to adhere to a solid surface (plaster, drywall, timber, or render), not a layer of loose debris. Your walls are a magnet for contaminants you cannot always see with the naked eye. Over months and years, they amass a “bond-breaking” film composed of:
- Microscopic debris and dust are spread by HVAC systems, ceiling fans, and open windows.
- Oils and cooking grease spread by air (even into rooms distant from the kitchen).
- Fingerprints and skin oils around light switches, doorframes, and corridors.
- Soap scum, hairspray, and humidity deposits in bathrooms and ensuites.
- Stubborn oily residues like nicotine or candle soot.
It is important to remember that not every wall needs heavy washing before painting. In many homes, a simple dust removal or spot-clean is enough, especially when there is no visible grease, mould, or stubborn staining. In cases where stains have penetrated deeply (such as heavy nicotine staining), cleaning alone may not be enough, and using a stain-blocking primer is the best way to stop the stain from bleeding through the new paint.
Tip 1: Scrub It (The Foundation of Clean)
Every nook and corner should be thoroughly cleaned with a soft scrub. In many cases, you only need to scrub areas that have visible marks, grease, handprints, or built-up dirt; however, the technique makes the difference between a DIY project and a professional finish.
The Two-Bucket Technique: To do this professionally, do not use just one bucket. If you plunge your dirty sponge back into the cleaning water, you are simply pushing dirt back onto the wall. Instead, use:
- Bucket 1: Cleaning solution (Sugar Soap or detergent).
- Bucket 2: Clean, warm rinse water.
How to do it properly:
- Dust First: Before wetting anything, use a vacuum with a brush attachment or a dry microfiber mop to remove dust. If you mix dusty walls with water, you end up with mud, which is much more difficult to clean.
- The Scrubbing Technique: Use a large cellulose sponge. Dip it in the cleaner and squeeze it out until it is damp, not dripping. Do not soak plasterboard walls or ceilings, as excess water can cause moisture issues.
- Wipe: Use clean water to wipe off the soapy residue. This ensures your new colour has good sticking power and prevents dust from being trapped underneath. After wiping, a dry cloth wipe-down or a short drying time (often around 15 minutes in warm weather) is usually sufficient before sanding and painting.
Tip 2: Removing Mould and Mildew
You must get rid of mould before any interior house painting begins. It can happen to almost any wall, particularly in damp places such as bathrooms, laundries, or rooms with no insulation.
Why you cannot simply hose it down: Ordinary cleaners may rub off the visible black spots, but the tiny roots (spores) in the plaster remain alive. If you paint over them, the mould will continue growing behind the paint film. With time, it will eat through the paint, causing it to bubble and flake.
The Expert Solution: The best DIY solution is to mix one part bleach with three parts water.
- Ventilate: Open the windows and wear a mask, as the fumes are dense.
- Wait: Spray the solution and allow it to sit for 15-20 minutes. This “dwell time” is essential to kill the spores in the porous plaster.
- Scrub and Rinse: Thoroughly scrub the area and rinse it well.
Caution: Never combine ammonia and bleach. If the mould is extensive or caused by a structural leak, you may need professional remediation before any interior painting can commence.
Tip 3: Wash It Good With Chemicals (TSP Heavy Duty)
Sometimes warm soapy water isn’t enough. In cases of excessive grease accumulation in kitchens or high-traffic areas, it is wise to clean walls before painting with something stronger.
What is TSP? Trisodium Phosphate (TSP) is a heavy-duty cleaner used by professional painters Brisbane wide. It is an effective degreaser that removes stubborn soils such as heavy grease, crayon marks, candle soot, and scuff marks. Sugar soap is often a more affordable option and remains very effective for most standard wall cleaning jobs.
Why use it? TSP acts as both a cleaner and a de-glosser. This is an added advantage for paint preparation, as it slightly dulls the finish of the old paint, providing the new paint with a “tooth” to cling to.
Safety: TSP is a powerful chemical, so you need to use rubber gloves and eye protection. It is slightly more expensive than dish soap, but it provides the cleanest surface possible, the best prep walls for painting technique for neglected walls. When cleaning plasterboard, always use a damp sponge instead of over-wetting the surface.
Tip 4: Sanding (The Smooth Finish Secret)
Sanding is a vital part of the painting process, yet it is the step most DIYers skip. While cleaning eradicates dirt, sanding changes the Sanding is a vital part of the painting process, yet it is the step most DIYers skip. While cleaning eradicates dirt, sanding changes the texture to ensure the paint adheres smoothly.
Why sand clean walls? Imagine trying to paint on glass, it slides right off. If your old paint finish was Satin, Semi-Gloss, or Gloss, it will be too shiny for the new paint to bond. You need to “de-gloss” it.
- Inspect & Feather: If your wall has chips, sand the edges until you can no longer feel the ridge where the paint flaked off.
- Scuff Sanding: Scuff the walls using fine-grain sandpaper (180 to 220 grit). You are not stripping the paint; you are just making tiny scratches to help it stick.
- Dust Off: You must wipe the walls again to remove the powder. If you paint over dust, your wall will feel like sandpaper.
Pro Tip: If this sounds like too much work, hire professional residential painters in Brisbane. We use dustless sanding machines to ensure the perfect substrate while keeping your home clean.
Tip 5: Allow Walls to Dry Completely (The Step That Often Gets Overlooked)
While cleaning is necessary, it is equally important to ensure that walls are given sufficient time to dry before painting any interior surface.
Why this is important:
If walls are slightly damp, paint will not adhere properly. This can cause blistering, peeling, or uneven paint surfaces over time, particularly on plasterboard and painted surfaces.
The best practices for interior walls:
- After washing, allow walls to dry naturally
- In well-ventilated and warm areas, drying usually takes 15-30 minutes
- In bathrooms, laundries, or humid environments, allow additional drying time
- Use fans or open windows to increase airflow if necessary
- Always ensure walls are dry to the touch before sanding or painting
Conclusion: Respect the Prep!
Whether you choose to DIY or contract us, keep this important piece of painting advice in mind: The actual quality of your paint job is defined long before you even open a paint can.
But do walls need to be washed before painting? Yes. Is it worth the effort? Absolutely. However, the amount of cleaning will also depend on the surface condition; some tasks will only require dust cleaning or light spot-cleaning, whereas others (such as kitchens, mould, or heavy stains) will require more preparation. With these tips in mind on how to clean, de-gloss, and dry your surfaces, your new colour will be bright, the finish will be smooth, and it will last for years before it peels. In cases where stains have been absorbed into the surface (as in the case of a strong nicotine stain), stain-blocking primers may be the only solution before repainting.
With these painting tips on cleaning, de-glossing, and drying your surfaces, your new colour will be bright, the finish will be smooth, and it will last for years without peeling.
Need expert help? Contact Painting by MOLI. As your local interior painters Brisbane experts, we provide high-quality finishes across the city. We do the dirty work so you can enjoy the lovely outcome.
