Underground Greenhouse Question

I am following Mike Oeher's design.

I have dug out my underground greenhouse, and have the posts and some of the wall framing installed. I have some plastic prepped at the bottom, and plan to pull it up over the outside of the plywood when I install the plywood. However, I have only a few inches between the clay wall, and the exterior of the greenhouse. What is the best way to affix the plywood to the wall?

Here are the ideas I had about it:

1. I could just fill with dirt and let pressure do push the plywood into place.

2. I could drill out a partial hole in the 2x4 studs and put some screws through the studs.

3. All of the above.

Thanks in advance. I am not much of a carpenter.

Edwin

I would toenail through the 2x4s from the inside Edwin. That should work fine since, as you said, the pressure of the earth once you get it backfilled will secure the sheathing. I would secure it though because the sheathing might get some horizontal forces working on it so I wouldn't just count on the earth. Best of luck on your project. Keep us posted on your progress.

A carpenter friend suggested a third option. Drilling through the 2x4 at an angle into the plywood. That worked well when I had enough wood to bite into. In some areas, I will try the toenail technique.