How to seal an almost flat/horizontal concrete roof?

[Vargklo]

I have a small patio that consists of a concrete roof on top of our garage. I got help from craftsmen to apply a seal about 10 years ago (two-component adhesive with mesh reinforcement), but now it has started to crack and let water in, causing it to drip from the ceiling in the garage below.

Any tips on an effective material to coat the surface with to make it watertight?

 

[Demmpa]

Welded rubber membrane, bitumen, roofing felt, metal covering?
And wood/composite decking on top?

https://www.tak20.se/takomlaggning/papptak/gummiduk-tak/
https://www.takcentrumbutiken.se/gummiduk/easy-cover/easy-cover-epdm-duk-for-taktackning
https://www.soprema.se/blog/epdm-gummi-eller-bitumen
https://www.tätskiktsakademin.se/materialkunskap/bitumenbaserade-tatskikt/

 

[Vargklo]

Thank you for the good and detailed options. Spontaneously, it looks like work usually done by tradesmen. Is there any of the options that you think a handy DIY enthusiast could tackle?

 

[sblixten]

Maybe rubber sheeting could be an alternative.
You can read here how I did it: https://www.byggahus.se/forum/threads/dammduk-pa-taket.294077/

 

[Vargklo]

Maybe rubber sheeting could be an option.
You can read here how I did it: [link]

Thanks - a good thread with a similar situation. Is it true that you bought everything from sealeco.com? Can you tell more about which components you bought and how the sheeting is attached, for example, just gluing at the edges or under the entire sheet? Did you have to call or email to know what to buy?

 

[sblixten]

I called and talked to them and they explained how I should do it.
If I remember correctly, I only glued the edges plus screws every 30 centimeters where it was possible.
They were very helpful and instructed me on how to do it.

Edit: The ground fabric that I placed under the rubber mat I bought from a local gravel pit.