Hi Freed,
I’m not suggesting that you should only use concrete. There are alternatives such as flagstones, bricks, paving slabs, timber, etc., but when talking about organic growing and the environment we also need to be practical.
You need to consider why your doing this and weigh that up against the perceived damage to the environment.
Your building a Greenhouse to raise plants not a structure to park your 4×4.
If we were to go down the road of banning the use of concrete in the garden altogether then how can we justify using polytunnels when you consider the vast amounts of plastic sheeting used in their construction?
I intend to build a Greenhouse this summer. It will be a timber and glass structure with flagstone floor. The foundation for the walls will be concrete. All the materials used in its construction with the possible exception of screws, nails and glue will be sourced from local quarry, forestry and glass manufacturer and when I weigh that against the insignificant amount of concrete I will use I believe I am gardening organically.
Don.