The most common solar installations are on rooftops, taking advantage of the existing structure for a faster installation with minimal hardware. Many roofs have some open space on the south-facing side that is not shaded or obstructed by vents or pipe.
Rooftop solar arrays are mounted and attached with the appropriate hardware designed for the specific roofing type (i.e. asphalt shingle, metal, tile, etc.). The hardware design is engineered according to the type of attachment needed, slope of the roof, and local wind/snow loads.
The distributed weight of a solar array is relatively low (only about 2.5 psf), so structural modifications are not required.
Roof trusses/rafters provide strong anchoring points, or in the case of metal standing seam roofs the attachments are made directly to the metal seam (no penetrations). On average about 1.3 attachments are needed per solar panel.
When properly installed, all types of roof attachments are waterproof for the life of the roof and are guaranteed to not leak or result in structural damage. In fact, the attachment location will become more waterproof than it was before.
Asphalt shingle roofs attachments may use a metal flashing that slides beneath the shingles, guaranteeing a dry penetration even in the event of shingle failure. Adhesive-flashing systems are also widely used, which provide a permanent seal by bonding to the shingle.
Metal roofs attachments are specialized for for the specific type of metal sheet, including ribbed, corrugated, standing seam roofs.
Tile roofs (concrete or terracotta) attachments replace individual tiles at each attachment point with a metal flashing that matches the shape of tile. Lag screws are used to attach to the rafter.
Flat roofs, where possible, may use ballasted solar mounts without penetrations; however these systems require maintenance and are unfavorable in snowy climates. Installing a custom structure is sometimes an option for flat roofs, which allows solar panels to be tilted up for better performance.
When rooftop mounting isn't an option, ground-based solar arrays can be a viable alternative.