Our house roof consists is made up of roofing metal and cement sheets. Out of the total area of the roof 50% is covered with metal sheets. This part of the roof also has good slopes for the rain water to drain off (This is because this part has a small tent shaped attic). The other 50% roof comprises of cement sheets. This part of the roof is more like flat surface with minimal slope for the rain water to drain off. There is a gap between where the metal and cement sheets meet. As they both have uneven surface and they do not match, hence even in the slightest rains there is leakage from this part of the roof. This is further aggravated by the difference in slope between these 2 surfaces.
How do I fill this gap with water proof material ? As this is exposed to the sun it would also need to be heat/sun resistant and crack resistant due to change in the metal length due to heat.