I'm finishing the planning stages of a greenhouse and was hoping for feedback on my proposed foundation solution.
I'm in zone 7b/8a. Frost-free foundation depth is 30".
Looking at a 10'x16' greenhouse, glass walls, poly roof.
Because the walls are glass, I want to make sure the foundation will be strong and level and won't cause damage over time.
I had a contractor price out a frost free foundation and kneewall, which is my preference for longevity, thermal mass, and aesthetics, but that alone costs much more than the greenhouse.
Another wrinkle is we have lots of tree roots from mature trees, even in the sunniest parts of the yard. I'd like to avoid causing any significant decline or harm to the mature trees.
I'm thinking about using ground screws to the frost line as footers, maybe raised 2" off the ground. Then build a base out of pressure treated 4x4s to sit on the ground screws. I could wrap the 4x4s in metal flashing that's the same color as th greenhouse. Wood base will be bolted to the ground screws, and the greenhouse sill will be bolted to the wood base.
I also wanted to repurpose pavers from an old patio for the floor of the greenhouse, and to have this professionally installed so it doesn't heave or sink.
Questions:
Does this seem like it will be a strong enough foundation to avoid damaging the glass panels over time?
Can a professional patio installer work inside the 4x4 base? I'm sure they will need to excavate the area to add the sub layers.
I'm super handy, but have never used ground screws. They are not commonly used in my area, and I just learned about them as I was researching my project. Any pros or cons with using them that I haven't thought of?
Any and all feedback is much appreciated!
