Hi Martin, We built a wall 20 plus yers ago and our siol is very light too, the wall was about 20 odd feet long and last year when we had 4" of rain in 24 or so hour the wall ended up in the next doors.
The pressure was that great and as i am a builder and built the wall to regulation standards it was only 3 feet high we just felt that maybe u could also have alot of rain and it may bhappen to u, Des
Des - The soil here in so sandy and well drained i diddnt bother, just a plastic sheeting to keep and damp away from the wall, did a test run with the hose pipe on for four hours and never even got a puddle!!
Martin
