It's not every day that you're in the market for a new garage door. So if you think you know what to expect when shopping for a new one or feel that current models are the same as your 15-year-old door, you're in for a surprise. Today's doors are stronger, more secure and better insulated, and they require much less maintenance than their predecessors. And you've never before had such a range of choice in materials, styles, colors and window treatments. Selecting a material. Most new garage doors are made of steel backed by rigid-foam insulation. Panels made of 24-ga. steel are the strongest (26- and 28-ga. steel is also used); most are produced with an embossed wood-grain pattern or with a smooth finish. Look for a model with a baked-on primer and polyester topcoat for maximum rust protection. Warranties for steel doors start at 10 years; limited lifetime coverage is not uncommon. Once the mainstay garage door material, wood has taken a backseat to other materials in the middle of the market. To a great extent, this is due to the added maintenance and regular painting wood doors require. Most wood doors are constructed with a hemlock frame and hardboard panels. But custom doors are often made from solid Douglas fir. The typical warranty for a factory-made wood door is one year; many custom doors are backed for 15 years. Plastic doors are fairly new to the scene, and they might eventually be the door of choice. Like steel, plastic doors offer lightweight durability without routine upkeep. Unlike their metal and wood counterparts, they're corrosion- and rot-free, and they operate almost silently. Because they contain UV-resistant additives, light-colored versions can take sun without fading. Gadco's polyethylene door is made from the same high-density plastic used for truck-bed liners. Overhead Door's Renata model, made of color-through PVC, offers a selection of panel designs that go well beyond the basic rectangle. Plastic doors carry 20-year or longer warranties.