There are typically two ways of fitting solar panels to roofs, depending on the angle of the roof. If it is a flat roof then a ballast system will be needed, where the panels are on frames that can be elevated, and the frames are held securely in place with ballast. On a pitched roof, a direct fixed system can be used. Panels are positively fixed into the underlying roof structure. Structural calculations will be needed for both types of fittings to ensure the roof can support the additional loads.