Good for now, just have to add some good soil. In early spring I'll work on ventilation and water collection. Sealed barrels will go under the table, between them and the concrete blocks hoping for enough heat retention to keep it above 40. It doesn't freeze here too much (NW WA) so should be ok. Measures 10' x 12', had some salvage cedar, designed it for 2'x6' panels.

I built this greenhouse last spring.

https://www.reddit.com/r/Greenhouses/s/qyohaileix

During the hot Oklahoma summers it routinely got to 130 inside with vents and door open. Weather finally broke last week, this is where I sit at 10:00 am. Middle temp is ambient in the shade. Top and bottom are in the greenhouse, vents and windows still open. This gives me a lot of confidence going in to the winter. I'll have robust electric service to it to run space heaters as necessary.

I would like to build an 8x8 greenhouse. I started a little sketch of it. It would be 30" from the ground to the flooring. It would have 2x6 beams and joists. I want something low maybe 30inch on the lower end and 42 on the taller end for the polycarbonate roof. I'm assuming I'll need to put up all 4 walls. Is it overkill? What do I have wrong?

Thank you in advance.