How to get water to go OVER instead of UNDER rocks??

[Meyer Jordan]

All spray foams expand. The key is not overly applying it. If sealing under a waterfall stone is the goal. Follow this procedure: Dry set stone to final desired position. Remove stone and lay about a 1/2" - 1" bead of foam the necessary length where rock will sit. Replace rock. Foam will expand blocking any passageway for water to travel under the stone. DO NOT overapply foam. This is the mistake many make. Lay a practice bead on a disposable piece or underlayment of liner first.
A little foam goes a long way.

 

[Meyer Jordan]

If the waterfall stone that you are using is lightweight, it may be necessary to place a larger rock on top to hold it in place as the expanding foam will exert enough force to move small rocks.

 

[tbendl]

Ugh, I can't move that dang stone 1 more time. I might be able to tip it forward and do that.
I will have to do the heavy rock for the upper falls though since I will probably use lighter weight rocks for that one.
Thanks Meyer!

 

[tbendl]

2 cans good for doing 2 sets of falls?

 

[sissy]

to me it looks like your side rocks should be up higher .The liner should always go up on both sides and should never seat straight and flat .It almost needs to look like a U with the water coming out in the bottom of the U .If you had 6 inchs on each side higher with the liner going up the sides it would work right /

 

[Usman]

If you can show us then people can answer accurately , how its constructed ..
as i understood if its a stream , what uil need to do is create small damn a resistance and rocks should not be that big , see the top of rock and water level should be similer level then it should overflow see pics to get idea , altho in nature the volume is too much we cant mimic that , we can narrow the opening of water the channel to be visible more , what i used once were small air tight bags with sand in it to block and left small openin where i places rounded rock to let water overflow it and added rest rocks on bags to hide

 

[Meyer Jordan]

2 cans good for doing 2 sets of falls?

For your size application, one can should be more than enough to seal two (2) waterfalls. Foam is like Bryllcream..."A little dab'l do ya". If you remember that, you are definitely getting long-in-tooth.