Which is best, mortar bedded or dry fix roof?

A dry fix roof offers many advantages over the traditionally mortar bedded roof. Mortar requires regular maintenance, whereas dry fix systems are maintenance-free. Dry fix systems also provide other advantages, such as mechanical fixing to ensure security against wind damage; also ventilation at ridge and hip. 

On some old traditional roof coverings or heritage buildings, mortar still has its place. But where possible it should be used in conjunction with other fixings such as nails, screws or clips for security. Although a strong mortar mix can resist wind uplift, if there is any movement within the roof structure then the mortar will crack and leave the fittings vulnerable to wind, whereas dry fix systems are able to cope with some structural movement.