Why Exterior Surface Preparation Is Critical
Exterior walls take a beating—rain, sun, frost, wind, and constant environmental stress all impact the integrity of your paint. So when you see flaking paint on an outside wall, you might think slapping on a fresh coat is the easy fix. But painting directly over flaky or damaged paint without preparing the wall—especially without using filler—is a sure way to end up with a short-lived, patchy, and uneven finish.
What Causes Exterior Paint to Flake and Fail?
UV rays, freezing temperatures, and driving rain all break down paint over time. Moisture can seep behind weak paint layers and cause them to lift or bubble.
Surface Movement and Ageing
External walls expand and contract due to temperature changes. This constant motion, combined with aging paint layers, leads to cracking and flaking.
Poor Application or Materials
Paint applied to dusty, greasy, or damp walls—or over incompatible surfaces—will not bond well. If your last paint job skipped the prep work, it’s no surprise it’s now peeling.
Why Painting Over Flaking Paint Won’t Work
Flaked areas create grooves and ridges that fresh paint cannot hide. These blemishes become glaringly obvious once a new coat is applied.
Immediate Peeling and Blistering
Without addressing the underlying issue, new paint won’t adhere. In a matter of weeks—or even days—you’ll see peeling again.
Wasted Time and Materials
Every litre of paint you apply without repairing the surface properly is money and effort down the drain.
The Right Way to Prepare a Flaking External Wall
Step 1: Remove All Loose and Flaking Paint
Use a sturdy scraper or wire brush to thoroughly strip all the loose and damaged paint. The aim is to expose only solid, stable surfaces.
Step 2: Fill All Imperfections and Cracks
Use an exterior-grade filler to repair all cracks, dents, and areas where paint has peeled away. Filler bridges gaps, smooths rough surfaces, and restores the wall’s structure.
Step 3: Sand the Surface for Evenness
Once the filler dries, sand it down until the surface is smooth and flush with surrounding areas. This ensures a seamless look once painted.
Step 4: Prime and Paint with Exterior-Grade Materials
Apply a masonry primer or stabiliser over the filled and sanded areas. This allows the paint to bind well and prevents future moisture ingress. Finish with a high-quality exterior paint designed to withstand weathering.
Why Filler Is Essential Before Painting
Flaking paint often leaves behind cavities or gouges. Filler restores these areas, giving you a level surface to paint on.
Creates a Level, Paintable Surface
Even premium paint can’t disguise damaged or sunken patches. Filler is what allows your topcoat to look even and professional.
Prevents Future Paint Failure
Filler doesn’t just improve the appearance—it enhances the paint’s ability to stick and last by reinforcing weak areas.
Common Mistakes to Avoid When Repainting Exterior Walls
Painting Over Dust or Cracked Substrates
Even the best paints can’t bond to unstable or dirty surfaces. Cleaning and preparation are non-negotiable.
Ignoring Small Cracks or Dents
They may seem minor, but these imperfections will ruin your finish and lead to peeling if not addressed with filler.
Skipping Primer on Filled Areas
Unprimed filler can absorb paint unevenly, leading to blotches or weak adhesion. Always prime first.
Tips for a Long-Lasting Finish
Use Weather-Resistant Paint
Choose paint specifically designed for masonry and external applications. Look for waterproofing and UV-resistant properties.
Apply Paint Only in Dry, Mild Conditions
Never paint on a damp wall or in direct, hot sun. Aim for dry, overcast days with moderate temperatures.
FAQs about Exterior Wall Preparation
Q1: Can I just paint over small flaked areas?
No. Even small patches need to be scraped, filled, and sanded for proper paint adhesion.
Q2: Is filler really necessary?
Yes. It’s the only way to repair damage and achieve a smooth, even result.
Q3: How long should filler dry before painting?
This depends on the product and thickness, but typically 2–6 hours. Always follow package instructions.
Q4: Can I use indoor filler for external walls?
No. Only use a filler rated for external applications—it resists moisture, frost, and UV damage.
Q5: Do I need to sand filler before painting?
Yes. Sanding ensures the surface is level and helps paint adhere properly.
Fix It Properly First – or Do It Twice
Painting over flaking paint on an external wall without properly filling and sanding first is a shortcut that will cost you more in the long run. Take the time to prepare the wall properly—scrape, fill, sand, and prime—and your finish will not only look better but also stand the test of time.
👉 Need expert help? Contact Kensington Maintenance to restore and repaint your exterior walls the right way, the first time.