Sealing garage roof - liquid bitumen?

Hello everyone,

I want to renovate my garage roof (prefabricated garage, flat roof, 18 years old) soon.
So far, there has been a makeshift bitumen coating. The roof doesn’t seem to have any cracks or similar issues.

Is it worth applying the coating properly again now, or is it better to choose another method?

If coating, which primer and which type of bitumen should I use? The selection is huge.

Many thanks for the advice!

Bitumen coating is rather not suitable for this. Either bitumen welding membrane or (PE?) foil

Better use a classic bitumen welding membrane. Affordable, proven, and durable. You can surely borrow the tools for it if you don't want to buy them or already have them.

Bitumen coating is rather not suitable for this. Either bitumen torch-on membrane or (PE?) foil

I have to convince my father that a coating is not good. For whatever reason, he is totally obsessed with it. What exactly speaks against the coating?

Better take a classic bitumen torch-on membrane. Inexpensive, proven, and durable. You can probably borrow the tools for it if you don't want to buy them or already have them.

How many euros can you expect to pay for about 30 sqm? The coating seems to be relatively inexpensive.