How to seal a leaking planter box?

[mitch0816]

Hi All,

My apartment has a courtyard with brick planter boxes. The issue I have is that whenever I water the planter boxes, some of the water leaks out onto the concrete pavement and pools there and is staining and degrading the pavement.

I

I presume that the water is leaking through these cracks and so whatever waterproofing it had has failed.

I want to seal the planter boxes to stop this leaking.

If anyone is able to suggest solutions to this, it would be much appreciated. Is it possible to seal it from outside without having to remove all the soil?

Thanks for any advice you can give.