Posted: 02/10/2016 at 11:05
Steve there are quite a few ways of anchoring a greenhouse down, my own is a lean to so fastened to a wall sitting on a brick base, its weight keeps it in place and has worked for thirty years. Some manufacturers make a steel base that anchors to the ground with long pins then build the green house on that, some make a concrete plinth others put down slabs and drill into them although advice should come with the green house.
Like you I had soil inside the greenhouse with a central slab walkway, after five years of changing the soil or topping up, the soil came out a membrane went in and a gravel bed put down. I got twice as many pots in on the bed it held water meaning the moisture level in the greenhouse was high beneficial for the plants and clean. A staging goes in for winter so plants can be overwintered both on the staging and under, a double use of the space. It is all up to you although a phone call or e-mail to the manufacturer of which ever is your choice of greenhouse will get an answer.