How to Prep Aluminum Siding for Paint — Step-by-Step Guide

The single biggest difference between a 4-year aluminum siding paint job and a 15-year one isn’t the paint — it’s the prep. Here’s exactly what proper preparation looks like before the first drop of finish coat hits the wall.

Step 1: Inspection & assessment

We walk the entire perimeter looking for: panel damage, chalking severity, areas of bare metal, caulk failures around windows and doors, trim damage, and any active rust or oxidation. We photograph every elevation and put findings on the estimate. If something needs replacement before paint, we say so up front.

Step 2: Pressure wash

Aluminum siding pulls dirt, pollen, mold, and decades of chalk that all need to come off. We use 1,500–2,500 PSI with a 25° tip, a mild house-wash detergent, and we work top-down. Higher pressure can drive water behind panels, so we tune carefully and use rotating tips on stubborn buildup, never on the siding itself.

Step 3: Drying

After pressure washing, the siding gets 24–48 hours to dry completely. Painting wet aluminum is the fastest way to trap moisture under the film and cause peeling. We test moisture before priming.

Step 4: Scrape & sand

Loose paint comes off with hand scrapers and 80-grit sanding pads. We feather edges of any remaining sound paint so the new coats don’t telegraph through. Heavily chalked panels get sanded entirely with fine pads to give the primer a key.

Step 5: Spot-prime bare metal

Anywhere we’ve scraped through to bare aluminum gets a coat of metal-bonding primer (Sherwin-Williams Extreme Bond or Insl-X STIX). Bare aluminum rejects standard primers — bonding primers are formulated to grip the oxide layer. This is non-negotiable.

Step 6: Caulk and seal

Failed caulk around windows, doors, and panel-to-panel joints gets cut out and replaced with a high-grade siliconized acrylic. Skipping caulk repair means water gets behind the siding and your paint job fails from the inside out.

Step 7: Mask & protect

Windows, doors, fixtures, lighting, vents, A/C units, and landscaping all get protected. We use plastic sheeting and painter’s tape — and we pull it the same day so adhesive doesn’t bake on. Decks and patios get rosin paper or tarps.

Step 8: First finish coat

Once prep is signed off, we apply the first coat of premium 100% acrylic latex by airless sprayer with back-rolling on textured panels for film thickness. Spray-only doesn’t bond as well to chalky aluminum — back-rolling drives the paint into the surface.

Step 9: Inspect, second coat, final walk-through

After the first coat dries, we inspect for missed spots, drips, or thin areas. The second coat goes on the next day (or same day if conditions allow), and a final walk-through with the homeowner closes out the job. Touch-up paint, leftover material, and color names get left with the customer.

How long does the whole process take?

For a typical 1,800 sq ft home: 3–4 working days end-to-end. Two-story colonials add 1–2 days. Weather can extend the schedule but never compresses it — we don’t shortcut prep to hit a date.

The bottom line

Every step above is in writing on every Broadway Painting Solutions quote for aluminum siding. If a competing quote skips even one of these steps, ask why. Your siding is too important to be a learning experience. Request your free estimate →