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How to Prep and Paint Aluminum Siding

This Old House painting contractor Jim Clark shares tips to help you clean and prepare your aluminum siding for a fresh coat of paint.

Before you paint aluminum siding, clean the surface thoroughly and prime the siding with one coat of acrylic primer. Then, paint with two coats of acrylic paint. In this video, TOH expert shares his tips and demonstrates how you clean and prepare the surface for painting.

Steps for Painting Aluminum Siding

1. Inspect the Siding for Mildew, Powdery Paint Pigment, and Mildew

  • Rub siding with cloth to check for powdery paint pigment and mildew.
  • Cover ground and nearby shrubs with drop cloths.
  • Test old siding paint for lead using a lead test kit; if lead is present, contact a licensed lead abatement specialist.

2. Create Your Solution and Clean the Siding

Wear gloves, then mix in a bucket a cleaning solution of one cup chlorine bleach, one cup TSP and one gallon of water.

There are three ways to clean the siding: scrubbing with a sponge, using a pressure washer, or a random-orbit sander.

Scrub with a Sponge

  • Soak abrasive sponge in cleaning solution and scrub siding clean.
  • When you’re done, rinse siding with garden hose.

Use a Pressure Washer

For large areas, use a pressure washer to spray cleaning solution onto siding.

  • Connect garden hose to pressure washer and attach a fan-spray tip to the washer's wand. Fill the washer's reservoir with bleach/TSP/water cleaning solution.
  • Aim the spray tip at an angle to the surface, pointing downward to avoid shooting water under the siding.
  • When you’re done, rinse the siding with clean water.

Use a Random-Orbit Sander

To remove paint from siding, use a random-orbit sander with a 100-grit abrasive disk.

  • Attach the sander to a wet/dry vacuum that’s equipped with a HEPA filter.
  • Use it on the siding and you may find that using this sands down to the bare metal—which would be the ultimate prep job. However, you may find this too time consuming so cleaning with a pressure washer will likely work well enough to get ready to paint.

3. Paint Aluminum Siding with Acrylic

After your siding dries:

  • Apply one coat of acrylic primer.
  • Then follow up by two coats of acrylic topcoat paint.
  • Remove drop cloths after painting.

Tools and Materials