build a brick herb box

[rasik77]

Hello
I am planning to build a brick herb box after my garden patio. The box will be 900mm high (from patio floor), 5 meters long with 300mm planting width between the brick walls. This will also act as a wall for the garden patio. The brick wall will be half brick (102mm) on each side.

I would like to know what I need to consider during the build. Is the brick wall structure (thickness) ok, water proofing, drainage, mortar mix etc? Your advice would be much appreciated.

Thanks
Rasik