These roof coatings are like paint. They have NO STRUCTURAL INTEGRITY.
IF you don't believe this, TRY putting it over beams WITHOUT something as a roofing UNDER it!!
MOST times it CAN be used directly over the roof sheeting WITHOUT installing a roofing such as shingles under it IF there is not too much slope! (The texture of the shingles tends to keep it in place so it does NOT "run" off before it drys.)
