I have an idea to build a Greenhouse on top of sand filled swimming pool. I’m only considering this because it is in a fenced enclosure next to a building with access to water and electricity. Plus the surrounding area outside the fence is a concrete parking lot. I’m thinking of digging out about 2 to 3 feet of sand, compact the sand as best as I can, place a rain permeable root barrier on top of the sand to allow drainage but prevent roots from growing past and to keep the top soil from washing away, then fill it in with finished compost. That is the most ideal but may be too expensive. The economical approach would be to compact the sand and place an impermeable EPDM of some sort then build raised wooden beds filled with compost container mix. I’m just afraid the sand will start shifting around and the beds will tip out of level. Has anyone had experience working on top of sand or if this sounds like a crazy idea? Might be better to put down something solid on top of the sand before building beds etc.
I don’t know where you are working, but if the pool has been filled for a number of years and there is rain, then what settling will occur has probably already happened. I would not want sand walkways, but putting compost in raised beds would be the better option. The “pool” is still draining through it’s drain unless there were holes driven through before filling. There is always the risk that the drain can plug and you might develop a water table. Unless you have a use for the sand you would excavate, going above gives you the ability to withstand potential water filing the pool (remember it will not require as much water to fill with the sand and you are going to add water for your plants.)
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