Painting Metal Siding on a Phoenix Mobile Home

This was an exterior repaint of a single-story manufactured home in Phoenix, and it's a good one to show because most people think you can't paint metal siding. You can. It all comes down to the prep. The home started out with faded, chalky tan-gray metal lap siding that had been baking in the sun for years, and it finished in a bold three-tone green that makes the whole place look new. Painting metal siding in Phoenix isn't like painting stucco or brick, so here's how we did it.

The home and the plan

The body of this house is horizontal metal lap siding, not the stucco you see on most Valley homes, and that one fact changes the whole job. Metal is slick, it's already coated from the factory, it oxidizes instead of crumbling, and it expands and contracts with the heat more than masonry does. So what you wash, what you prime with, and what kind of paint you use are all different. There's also a covered carport with exposed beams and a ceiling to handle. We mapped it as one job: wash, scuff, seal, prime, paint.

Step one: wash off the chalk and oxidation

Old metal siding doesn't peel the way wood does. It chalks. The sun breaks down the old finish into a powdery layer you can wipe off with your hand, and fresh paint will not bond to that. So the first thing we did was wash the whole house down to cut through the chalk, the oxidation, and the dirt, and then let it dry completely. If you skip this and paint straight over chalk, the new coat takes the old powdery layer down with it in a year or two. The wash is the foundation of the whole job.

Step two: scuff, de-gloss, and seal the gaps

Factory metal siding has a slick, semi-gloss finish, and paint doesn't grab a slick surface well. So after it dried we scuffed and de-glossed the siding to give the new coating something to bite into. Any spots showing rust got wire-brushed and sanded back to sound, bright metal, then spot-primed with a rust-inhibitive metal primer. You have to get down to clean metal, because if you paint over active rust it just keeps corroding under the new film and pushes the paint back off. Then we sealed the gaps and seams with an exterior-grade caulk. You can see the caulk tubes in the work photos. On metal, sealing the seams keeps water out from behind the panels, which is where corrosion starts.

Step three: a bonding primer made for metal

This is the step a metal repaint stands or falls on. We primed the siding with a bonding primer built for metal, a direct-to-metal acrylic, not a standard wall primer. A bonding primer is formulated to grip slick, previously coated surfaces and give the topcoat a surface it can actually hold onto. The bare and rust-treated spots got their primer too, so nothing would telegraph through the new color. Skip the right primer on metal and even good paint will sheet right off it down the road. The primer is what makes the rest last.

Step four: the three-tone green scheme

With the house washed, sealed, and primed, the color went on, and the owner went bold. We laid down a light sage green across the main field of the siding, then a deep forest-green band along the lower portion of the walls like a wainscot. The trim, fascia, carport posts, and the beams under the porch all went a deep green to frame it, and we left the doors white so they pop as clean accents against all that color. Over the primer we put two finish coats, because one coat of a color this bold over siding this faded would have looked thin and patchy. The result looks deliberate, not just freshly painted.

For the topcoat we used a quality exterior acrylic, and that choice matters on metal. Metal expands and contracts as it heats up and cools down through an Arizona day, and a flexible acrylic moves with it instead of cracking. A stiff, brittle coating would split along the panel seams the first hard summer. Acrylic also holds its color against the UV here better than a cheap paint, which is what you want when you've committed to a real color like this.

Doing it right in the Phoenix summer heat

This was a June exterior, in the heat, and metal makes that trickier, not easier. A metal wall in direct Phoenix sun gets far hotter than the air around it, often well past what the paint can take, and paint applied to a surface that's too hot skins over before it can bond. So we chased the shade around the house and worked each wall when it was off the direct sun, checking the surface temperature instead of just the thermometer. The light sage we chose for the main field helps too, because a lighter color reflects more heat than a dark one and won't run as hot on a metal wall once it's up.

The result

The home went from a tired, chalky tan box to a clean, bold green that looks brand new from the street. The metal siding, which a lot of people would have told the owner to just live with or replace, took the new color beautifully because the prep underneath it was done right. You can see the before, in-progress, and finished photos in our gallery.

This job was all about our exterior house painting and the surface prep and repair that makes an exterior repaint actually last. For more on the products and color choices behind it, see our guides on why exterior paint chalks and peels in the Arizona sun and exterior colors that keep an Arizona home cooler.