Second floor terrace has gaps between slabs for drainage. What should I do?

[Martur]

Hello! I have a second floor terrace with big gaps between the slabs for drainage. Weeds grow there non stop. Last year I bought a compound to grout them but my father in law advise me to leave the gaps to allow drainage so I never ended up using it.

The other day I just thought I would sow some nice chamomile seeds between the gaps to distract from the weeds. Is this a good idea? If so, shall I put soil between the gaps?

Thank you

 

[Why Not Indeed]

If weeds already grow there then it sounds like you don't need to add soil. Pebbles or coarse gravel might be a better growing medium than nothing at all and would impede drainage a lot less than soil.
But if you really need the gaps for drainage, then you should be keeping them clear, right?
Perhaps you could compromise and keep the horizontal ones clear and plant in the vertical ones?