My greenhouse

I just bought two of these.

I intend to combine them, bolting together length wise, and removing and sotring the extra middle panels. Essentially making it a 12×12 greenhouse.

For the foundation im planning on doing 4x4s around the edges, and down the middle. Im going to paint/cost them agaisnt moisture and rot from the ground.

The greenhouses will have seperated floors, which i intend to find a good vinyl or plastic sheet/tarp for a mositure barrier. Im going to slope them downwards towards the back middle, where they will terminate at a drain pvc pipe woth holes in it, which will drain into the soil. Lastly, round river rock ontop l, leveled as the walking floor.

I got more planned, but this is the initial setup, but i do need some help on some stuff.

1. Im trying to find a solid anchoring bolts for the 4x4s to the ground. Something that corkscrews down, my area is high wind.

2. Anyone have any products they recommend for treating the 4x4s for long term rot prevention?

3. What kind of tarp or vinyl sheet would you recommend for durability and moisture/animal proofing?

4. My area can get heavy snow. Thinking of getting some long metal pieces and bolting to the vertical supports for more rigidity. Anyone have experience with these type of greenhouses?

5. Any comments or suggestion welcome.