I'm no stranger to building structures. I have built one work from home office on concrete piers 10×12, one storage shed on a concrete slab 7×13, one two story tall raised playhouse on 6×6 posts 10×12, and one chicken coop on raised 4x4s 5×10.
My wife has just acquired a Costco greenhouse, the 8×10 version. And we have either a concrete slab that is cracked in the middle and slopes down 7 in over the diagonal dimension of the greenhouse, or we can dig a New foundation in the side of our Hill which would have a 20 inch drop and possibly require some retaining wall blocks uphill and downhill.
At least with digging a New foundation I feel like I have a good handle on what is needed (would do a 13x 10 ft so there's space around the outside of the greenhouse. Dig 10 inches down on the uphill side, pile that to the downhill side. Put in retaining blocks at least 14 in high on the downhill side. Fill the space with about 4 inches of crushed gravel, not river rock, compact the gravel then assemble the greenhouse in place.
If I wanted to make use of the existing concrete slab that is 11 ft by 15 ft, then I'm not really sure how I would put a foundation on top of it that is also level, which is why I was thinking that starting from scratch might actually be easier.
Here are some pictures of the site as well as an initial test digging to see what the condition of the soil is. What is the collective Gardener's thoughts about this location and the difference between making use of the existing concrete slab versus building from scratch?
by RobinsonCruiseOh
2 Comments
Knowing where the sun is as it moves across the sky in the various seasons is of major importance. Greenhouses need sun and the larger dimension should face south. From that you can determine greenhouse placement.
If the slab you have meets that requirement then I’d use that for the greenhouse. You can patch the crack and raise the corner to level. There are companies that use foam for this. May be a DIY as well.
ETA Water source is another consideration for greenhouse placement.
The concrete slab is ideal, but dark-colored gravel will work as well, but I agree that you need the long side to face South.