Me and the other partners here at Greenshire plan to build a greenhouse
, sticking to Mike's design as closely as possible. I have his book and have read through it but didn't find answers to my questions.
Our problem is that we have a high water
table. The soil is about 3-4 feet of sandy loam, and then it hits a chalky, gravel/clay mix that doesn't drain well. Mike Oehler
's design calls for the design to be 4 feet below ground at the front, and 2 feet below ground level at the growing area. I should
mention that the site for the greenhouse
is on almost completely flat ground. Late last summer we dug a test pit 4 feet down and next spring thaw water filled about 3 feet deep at worst, levelled off to about 2 feet deep during mid-spring and then disappeared when the heat of summer came on. This excessive accumulation of moisture could have purely been from the pit being exposed to the elements, and could have been mostly melted snow which wouldn't enter the equation if there's a greenhouse
overtop. But it also could have been made up of significant amounts of ground water. I'm not sure.
If my worst fears came true and I did get standing water in the area inside the greenhouse
, wouldn't it all just collect in the deepest area at the front walk in space, leaving the growing area saturated but still suitable for plant growth? I don't mind having to wear waders . Would this amount of water compromise the structural integrity, even if we followed Mikes instructions to a tee?
In an effort to avoid standing water...Would I lose too much R value if I raised everything up by 2 feet, so that the front walk-in section is 2 feet below ground level, and the growing bed is at ground level? I would shore soil up around the structure over-top of the existing ground level but I'm worried that wouldn't be enough
to match the heat value of the 'by the book' depth.
Thanks for your input.