A roof keeps out wind rain, snow, hail, and the sun's light and heat. To accomplish this, a roof's surface must be watertight and durable as well as flexible enough to adapt to temperature changes without cracking or otherwise losing its integrity. In some areas, roofs must also be fire-resistant.

Roof framing can be simple or complex, depending on the style and decorative elements. It provides the skeleton for the covering materials. Roofs are sheathed with plywood or oriented-strand board (OSB) panels, or spaced boards for wood shingles.

Roofing felt, a heavy black paper saturated with asphalt, lies between the sheathing and the finishing material. It keeps out any water that might seep through the finishing material, yet allows moisture from inside the house to escape. Flashing keeps out water wherever finishing material connects with chimneys, dormers, or other roof planes.

Finishing materials may be as simple and utilitarian as asphalt shingles or as functional and decorative as wood shingles or tile.

Proper insulation and ventilation beneath a roof is key to keeping a home comfortable and in protecting the roof's structure from moisture damage.