I wouldn't count on just the foam. It's supposedly something like 95%
water-blocking. My experience on a waterfall that cascades through three
pools with about 8' of drop substantiates this. In my case, the foam directs
MOST of the water over the falls, but not all of it.

As far as what WILL work, I have no experience with this, but they make
those fake-rock waterfalls waterproof using concrete (textured with a
rock-like pad), then painted with waterproofing, then painted. Maybe you
could bridge the gap that way. You'd still have a joint between concrete
and rock though.You can't jack the flat rock up, and slip liner underneath?


"grubber" wrote in message
news
How waterproof is that stuff? I'm putting in a stream and there are many
wide flat limestone rocks that I would like to incorporate, while using
EPDM
liner for most of the stream. In particular, there is a rock about five
feet in diameter, about 4 inches thick that has a nice overhang. I would
like to dig the dirt back about a foot, lay liner back under the rock and
foam the seam where liner meets rock so I can have the stream flow over
the
rock and fall to the pool below.

Will the foam be good enough to waterproof the seam so I can have standing
water there, or only enough to deflect splashing water with the water
level
lower than the edge of the liner? Is there a better way to do this? I
know
I can do the Gatorgard spray-in stuff, but that's on the pricey side of
things.