
There is no need to have a drainage system.
How to build a greenhouse base using paving slabs. This could be made from breeze blocks paving slabs or concrete. What i am saying is the greenhouse changes as its use also changes putting it onto a permanent slab base will reduce your options in the future you are tied to a pave floor or dismantle and rebuild. If you need to open or adjust the spacing s simply stand on the slab you don t want to move and use a spade to lever the opposite slab into position. Give a lot of thought to what you wish to use it for independent fastening down will give you many options for the future frank.
The next option is to build a solid perimeter for the base to sit on. The best foundation option is to build a perimeter base foundation using pressure treated wood or paving slabs. You will lift the greenhouse above the ground level and still can grow plants directly from the soil. I hope this guide helps you to get an idea about different greenhouse foundation options.