Hi, I am currently landscaping my garden.I am leaving the lawn down because I am raising the level by 6". I have ordered some crushed concrete to raise the level by 4" and then put 2" of crushed slate down on top of this. I have been given some 500mu visqueen to cover the area which I intend to put holes in to allow water to soak away. My question is would it be better to put the visqueen on top of the lawn ,then put the crushed concrete down and then 2" of slate or would it be ok to lay the crushed concrete on top of the lawn,then put the visqueen down and put the slate on top of that.Thanks for any advice