Why can some tiles be used at a lower pitch?

The weather tightness of roof tiles and slates decreases as the roof pitch gets lower and rafter length increases because it takes longer for water to drain from the roof. The reason our tiles can achieve such a low minimum pitch is because we put them through very extreme testing processes, which go above and beyond what a normal roof tile would be exposed to. Many of them also incorporate special features which allow them to be installed at a lower pitch.