Just to preface... I have no experience whatsoever with the topic. That said...

Terra cotta, unless glazed, is a very porous material and will actually let water pass through it completely. I wouldn't make a waterfall out of it because of this. The potsherds, with their potentially hazardous points and edges, don't inspire confidence either.

Real rock, inert synthetics, and portland cement based concretes and the like are all much less water permeable than terra cotta and other such unglazed fired earth products.

[ Show Entire Thread ]