Revisions log for Answer #2075

There is a roofing felt "armored", i.e. sprinkled with stone chips on the outer side.

This allows you to strengthen it, make the color lighter, so that it is not so heated in the sun, so that, being in a roll, it does not stick during transportation, etc...

According to modern technology, it must be glued to the mastic, applied on the "underlay" soft roofing felt.

It is beneficial to the manufacturers, so that instead of one roll you buy two. The same story with soft shingles, but has a place to exist, because. One – it strengthens the thickness of the roof. Second – the first layer will be solid. Third – does not spoil the appearance of expensive soft shingles. Fourth – a guarantee of waterproofing coverage.

I would, in the case of conventional roofing felt, not buy a substrate, and for soft shingles I consider its use is necessary. It's up to you to decide.