A steel garage door facing south can reach surface temperatures above 150 degrees Fahrenheit on a July afternoon. By midnight, that same surface drops to ambient, sometimes 80 degrees cooler. The panel seams expand and contract with every cycle, the metal flexes, and any paint system that cannot move with the substrate will fail at those seams first. Most garage door paint failures start at exactly that point: cracking along the panel perimeters where the stress is highest, followed by peeling as water works under the edges. The solution begins before a brush ever touches the door.

Prepping a Metal or Wood Garage Door for Exterior Paint

Garage door prep is not one process. It depends entirely on what the door is made of and what condition the existing surface is in.

Steel doors with factory paint still in good condition need cleaning, light abrasion, and a bonding primer before any topcoat. Wash the door with a TSP substitute at one quarter cup per gallon of water to remove grease, exhaust film, and chalking from old paint. Pay particular attention to the bottom panels, where road salt, winter grime, and exhaust accumulate in a heavier layer than the rest of the door. Rinse completely and allow at least 24 hours to dry before sanding. Lightly scuff the surface with 120-grit sandpaper or a synthetic abrasion pad to break the gloss and improve primer adhesion. Wipe down with a tack cloth afterward.

If the existing steel door finish is peeling, flaking, or shows any rust, the approach changes. Light to medium rust is addressed with Krud Kutter Must for Rust, which contains phosphoric acid and converts oxidation to a more stable compound within roughly 10 minutes of contact. Wait at least an hour after treatment before priming. Heavy rust that has created pitting or penetrated through the metal requires grinding or wire-brushing to remove loose material, followed by a rust-inhibiting primer like Rust-Oleum Protective Metal Primer.

Bare aluminum or galvanized steel doors need a direct-to-metal primer before any topcoat. Benjamin Moore Ultra Spec DTM Acrylic Enamel can be applied directly to properly prepared bare metal, including aluminum and galvanized steel. Zinc-based primers offer an additional layer of rust protection for steel panels in coastal or high-moisture environments.

Wood garage doors require a different sequence. Raw wood needs end grain sealed first, since end cuts absorb primer at two to three times the rate of face grain and will bleed moisture and stain without sealing. Apply a full coat of Zinsser Cover Stain or KILZ All-Purpose oil-based primer over the raw wood. Allow the oil primer to cure for one hour, then sand lightly with 150-grit before applying a second primer coat. Two primer coats on bare wood is not excess. It builds the film thickness that protects against seasonal moisture cycling in the door’s frame members.

Fiberglass doors present their own prep consideration. The gel coat surface is non-porous and requires a bonding primer to hold topcoat. INSL-X Stix Waterborne Bonding Primer and the Benjamin Moore STIX primer are both professional choices for fiberglass adhesion. No sanding is necessary with a bonding primer on clean fiberglass, but the surface must be degreased completely before priming.

Choosing Paint That Resists Expansion and Contraction

Oil-based paints are the wrong choice for garage doors, regardless of door material. As an oil-based paint film ages outdoors, it crosslinks and becomes increasingly rigid. On a surface that expands and contracts daily with temperature changes, a rigid paint film cracks at seams, panel perimeters, and any area under mechanical stress. This brittleness is not a defect in the specific product. It is the inherent behavior of alkyd chemistry when exposed to prolonged outdoor weathering. The brittleness develops gradually, but on a sun-facing door experiencing 80 to 100 degree surface temperature swings seasonally, it accelerates.

For metal doors, the correct topcoat is 100 percent acrylic latex, preferably a semi-gloss or gloss sheen. Semi-gloss and gloss sheens outperform satin on garage doors for two reasons. First, they shed moisture more effectively and are easier to clean of the exhaust film and road grime that accumulates on doors near driveways. Second, they flex better than high-solids flat formulations under thermal cycling because the film remains somewhat elastic throughout its life.

Benjamin Moore Aura Exterior and Sherwin-Williams Emerald Exterior are both top-tier acrylic choices for garage door topcoats. Both contain high levels of titanium dioxide for UV resistance and use acrylic binder systems that remain flexible as the film ages. Aura carries Color Lock technology with infrared-stable pigments, which is particularly relevant if you are painting the door a dark color. Dark pigments absorb significantly more infrared energy than light colors, driving surface temperatures higher on sun-facing doors.

For wood garage doors where a painted appearance is desired but longevity concerns are high, a solid-color exterior wood stain like Sherwin-Williams WoodScapes performs well. A penetrating solid stain forms a thinner film than paint, which means there is less material to crack or peel as the wood moves. The trade-off is a less hard surface that scuffs more easily. For homeowners who repaint every five to seven years anyway, a quality 100 percent acrylic topcoat is the better choice.

For color selection on any sun-facing door: lighter colors extend paint life measurably. A white or off-white door with an LRV above 70 absorbs dramatically less solar energy than a deep navy or forest green. If the aesthetic requires a dark color, verify the paint is formulated with infrared-reflective pigments and expect a shorter repaint cycle.

Painting a Garage Door in Sections Without Lap Marks

Garage doors are divided into horizontal panels by design, and working panel by panel is the correct technique. Attempting to roll the entire door surface from top to bottom without managing wet edges produces visible lap marks where the paint in one section begins to dry before the adjacent section is rolled out and blended.

Work from the top panel to the bottom. On each panel, start by cutting in with a two and one-half to three-inch angled brush around the recessed details, molding, and any trim elements. Get the brush into every corner and recess. The recesses in raised-panel doors are where paint accumulates in excess and where brush marks are most visible, so take time to tip off any heavy buildup with light, long strokes before moving to the flat face.

After cutting in on a panel, fill the flat face immediately with a nine-inch roller using 3/8-inch nap. Roll horizontally in overlapping passes, covering the panel while the cut-in edges are still wet. Maintain a wet edge by moving quickly. If you are using a slow-drying paint in high humidity, you have more time. In direct afternoon sun and low humidity, the window for wet edge blending shrinks to a few minutes. Under those conditions, apply thinner coats to stay ahead of the drying time.

Tipping off the rolled surface with a wide brush, using light strokes in the same direction, produces a superior appearance to roller stipple alone. The brush marks from tipping are finer and more even than the texture left by the roller nap, and they look more appropriate on a door surface viewed at close range.

Apply one coat of primer and two coats of topcoat. Thin topcoats are better than thick ones on a door. A thick topcoat applied in a single coat is more likely to sag on the vertical panel faces and more likely to crack at the seams under thermal movement than two thinner coats that cure incrementally.

How to Paint a Garage Door Without Removing It From the Track

Most residential garage door paint jobs are done in place, and this is manageable with the door closed in the down position. Work with the door fully closed and latched to keep it stable. Open doors sway and flex, making brush work on the upper panels difficult and creating uneven coverage where the door moves during application.

Before starting, close the door and disconnect the automatic opener if the door could be accidentally activated during the job. Post a note on any interior entry to the garage warning that painting is in progress. A door that travels up while paint is wet on the track side creates a mess and potentially ruins a panel.

Protect the tracks, hardware, and springs with painter’s tape and plastic sheeting. The tracks run alongside the door on both sides, and overspray or brush drips that get onto the tracks create friction points that wear the rollers. Tape off the rubber bottom seal as well. Most exterior paints do not adhere well to flexible rubber, and paint that flakes off the seal lands on the driveway every time the door opens.

For spray application, a detail tip of 411 or 413 on an airless sprayer is the right size for door panels. Keep the gun 12 to 18 inches from the surface and move consistently to avoid runs in the recesses. Spray from one side of the door panel to the other in horizontal passes, back-rolling immediately after spraying each panel section to work the coating into any texture and ensure even coverage without heavy spots at the panel centers.

For brush and roller application without spraying, the process is entirely viable and produces a high-quality result. A four-inch roller handles the flat panel faces efficiently, and a two-inch angled brush covers the recesses and edges. This combination gives more control over each panel section and reduces the risk of runs in the recessed areas.

The bottom foot of the door, including the seal channel and any raw metal on the door’s interior face that faces the garage floor, should be primed with a rust-inhibiting primer. This area is the most exposed to moisture from rain splash, snow melt, and condensation, and it is the first place steel doors begin to corrode at the base.