As you can guess I want to find out how to build a leakproof
waterfall. So if anyone has any tips they would be greatly
appreciated.
Firstly let me explain my concept.
I want to build a natural rock waterfall about 12 feet tall and about
16 feet wide at the top. I'll be using large rocks (grey limestone)
which will be at from about 2 foot long , 2 foot wide and about 10
inches thick upto about 6 feet long and 3 feet wide and also about 10
inches thick. We have a crane and a large telescopic lifter so we'll
be able to move and place them without too much back ache. I was
planning to first build a large mound out of topsoil and have the
digger driver roughly shape out the area for the rocks, essentially
some shelves to hold the rocks on. Then I was going to cover the
entire area with soft sand, cover this with a protective fleece and
then lay a layer of butyl rubber liner, then another layer of
protective fleece on top of the liner. Then before we placed the rocks
I was going to spray the underside with expanding foam, just to make
sure the liner didnt get punctured by the weight of the rocks. Next I
planned to use a cement mix (with some kind of polysomething aditive
to prevent cracking) with a final layer of waterproof paint.
The idea is that all the water from this waterfall will flow into a
large pond which we plan to construct similarly (sand, protective
membrane, butyl rubber liner, protective fleece, concrete, waterfproof
paint).

I know this is an abitious project and a reasonable budget has been
set aside but we want to get it right first time. I discussed the
pumps and filtration systems already and thats solved. My worry is
will this layered construction method work or should I try some other
method. Bottom line is whatever method we choose it has to work 100%
from day one.
Any thoughts greatly appreciated.