On 14/05/14 12:43, Martin wrote:
On Wed, 14 May 2014 11:32:09 +0100, "P Jameson" wrote:

Got one of those walk in plastic greenhouses. The floor is just earth and
so I've got a few one and half foot square plywood boards to put down as a
flooring.

Will they last well enough to just lie down straight on the soil or should I
put some plastic sheeting underneath, so they might last longer and not rot
from the damp?

Are they outdoor quality ply of marine ply?

Marine ply is very uncommon - they are likely to be either one of the
ordinary internal grade ply or WBP (water-boil-proof) which is OK for
external applications.