There are many options for the greenhouse foundation. Materials include concrete, concrete block, railroad ties or treated timber. This treated timber greenhouse foundation, anchored at the corners and sides, is set on gravel with a wood path down the center. It is being checked to be sure that it is square.
For the greenhouse floor, gravel on dirt is best. The aisle can be pavers, stone or bricks set in sand. We don’t recommend a concrete pad because moisture from the greenhouse can make it slick.