Do I Need To Pillar / Double Skin this Wall and Damp Proof it?

[Skavenger]

Hi,

I am building a small shed / workshop in my garden. Here is the link to the project.
I have just demolished an existing wall as the footing are stepped and not deep enough to use the wall for my shed.

The original wall and the new wall will retain a certain amount of earth on the outside consisting of a rockery and a multi stemmed tree.

1. When I build the wall should I add some pillars by doubling up on the blocks?
2. Before I put the earth back against the wall should I (a) render the wall or (b) line the wall with some polythene or DPM?
3. My footings will be approx 300mm wide and 200mm deep?

Here is the area where the wall is going. The old footing is still in place in the pic - it has since been removed.

 

[Ian H]

A gap would be best but we used some plastic boards next to our garage and that's been fine for years.

Rain water came through the opposite wall which was a standard dense block wall.