Valleys have always been a problem on roofs, this is due to the traditional sand and cements inability to flex. In these particular areas on a roof there is more movement and often cracks will appear in the mortar.
FlexiPoint is ideal in these areas as it will not crack but will flex with the excessive movement especially in the Valley areas of your roof.
Valleys are the most vulnerable areas on a roof as the main valley material is often made of steel or lead which the traditional mortar will not bond to. FlexiPoint will bond to the steel and lead and will also expand with the different expansion rates of the materials without cracking therefore making it the ideal product to use.
In most cases the problem with copings is the mortar joint will crack due to movement of the roof structure, once it cracks the water can run in the joint and into the cavity. The use of Flexipoint prevents this as it bonds to the coping stone and will flex with movement of the roof therefor preventing further damage.