How to Paint Aluminum Siding

Having spent years as a furniture refinisher, I’ve had plenty of opportunities to spray-paint metal objects, such as wrought-iron furniture, auto body parts and home appliances like stoves and refrigerators. I learned that getting good results involves careful surface preparation, controlled spray conditions and high-quality, expensive paint intended only for use on metal.

Fortunately, none of that applies to aluminum siding, and that’s a good thing, too. Otherwise, many homeowners would have to live with their chalky siding, with its chipped and flaking paint, rather than repaint it. In fact, there’s no reason to feel squeamish about repainting aluminum siding because you don’t need high-priced paint or special painting techniques. Aluminum doesn’t rot or crack, so prep is often easier than it is when repainting some other types of siding.

If you like, you can do the job with a brush and roller, which isn’t an option when applying solvent-based metal paint. Even so, I prefer to use a handheld airless sprayer, which takes less effort and helps the siding retain its metallic luster. Either way, prep is still very important if you want the paint to last.

This post provides tips to freshen up your home’s exterior and do an ace job.

Tools You’ll Need

• Garden hose/pressure washer
• Paint scraper
• Power sander
• 100-grit sandpaper
• Caulk gun
• Paint tray
• Foam paint brush
• Paint roller
• Airless sprayer (optional)

Materials You’ll Need

• Trisodium phosphate (TSP) or a TSP substitute
• Weatherproof patching compound
• Acrylic latex caulk
• Paint thinner
• Canvas drop cloths

Best Paint for Aluminum Siding

No…you don’t need toxic, solvent-based metal paint. The best paint for aluminum siding is good old water-based acrylic latex. It has more flexibility than 100-percent acrylic paint — which is also an option — allowing it to resist cracking as the metal expands and contracts in changing temperature conditions. Choose a premium product, because there’s no sense scrimping to save a few bucks if it means repainting in a few years, and check the can to make sure the product is recommended for metal siding.

You may also need a primer. Unfortunately, the best primers for aluminum siding are solvent-based, so you’ll still need that can of thinner for cleaning up. You can skip the primer if the existing paint is in good condition, but you need to prime if any bare metal is exposed. Primer is also a good idea if the surface is corroded, pitted, or otherwise poor condition. On a less-than-perfect surface, primer is insurance against chipping, flaking and cracking in the future.

How to Prepare the Siding

Before you apply paint, the siding must be clean, dry and free of mold. However, before you get to cleaning, you must remove any flaking or chipping paint from a previous paint job. You can do this with a paint scraper. After you remove the paint, go over the edges of the damaged area with a sander and 100-grit paper to flatten the edges.

Aluminum siding tends to dent, which is one reason why it’s not as popular as it used to be. Fill the dents with an exterior patching compound, such as DAP Weatherproof Patching Compound or Bondo Body Filler, and sand the repairs smooth with your sander. If any parts of the siding are corroded, use a patching compound to fill the holes. While you’re at it, replace any missing caulk around doors and windows with acrylic latex caulk.

Wash the Siding

Old aluminum siding tends to develop a chalky surface, and because the chalk interferes with paint adhesion, you need to wash it off. At the same time, you’ll be removing dirt and mold that have accumulated over the years.

• Use a power washer or garden hose to remove the bulk of chalk and dirt from the siding. Keep the nozzle of your power washer pointed straight at the siding or slightly down to avoid spraying water behind the siding slats and onto the sheathing.
• Scrub away difficult-to-remove dirt with a solution of 1/4 cup of TSP (or a TSP substitute) per gallon of water and a scrub brush. Work in manageable sections from the bottom up, and rinse the area you just cleaned with a power washer or hose before moving on.

Safety first: TSP is caustic, so wear rubber gloves and goggles while using it. Protect surrounding plants with canvas drop cloths.

Apply the Paint

You can apply the primer and the paint with a brush and roller, and if you do, use a foam brush rather than one with bristles to avoid brush marks. I prefer a handheld sprayer, which means masking doors and windows and refilling the one-quart cup frequently, but I’d rather do that than repeatedly reloading a paint roller. A sprayer also gets paint in tough-to-reach places — like directly under the edges of the slats — with little effort. And if you can find a cordless sprayer you like (I’m a fan of the Ryobi model), it’s super easy to use from a ladder.

Here’s a rundown of the procedure

• Apply the primer using a brush, roller or sprayer. You seldom have to apply it over the whole house — just in places where bare metal is showing or where you’ve made repairs. When brushing or rolling, always stroke in the direction of the siding.
• Let the primer dry, which usually takes from two to four hours. You seldom need more than one coat, but if you do, apply a second coat in the same way and let it dry.
• Spread the first coat of paint. Calculate the square footage before you start and make sure you have enough paint on hand to cover the entire house.
• Apply a second coat in the same way, if necessary, after the first coat has dried to the touch.
• Clean up all your tools with water or, in the case of primer, an appropriate thinner, immediately after finishing. That way, they’ll be ready the next time you need them.

FAQs

How long does paint last on aluminum siding?

This depends on the quality of paint you use, but at a minimum, it will last from six to 10 years. Some top-quality products can last 20 to 30 years.

How much paint do you need?

Typical coverage is between 200 and 400 square feet per gallon. Aluminum does not absorb paint, so you’ll probably get the maximum coverage listed on the label. Measure the square footage and divide by that number to get the number of gallons you need, then add an extra one just in case.

When is the best time to paint?

You need dry weather, obviously, but also temperatures that aren’t too cold or too hot. Paint can flash dry at high temperatures, increasing the possibility of cracking, so choose a mild, not-too-windy day to paint. The ideal working temperature is between 65 and 75 degrees.