I hope you are well.
I've scoured the internet for a good answer to this, but can't find anything definitive and keep reading contrary articles and recommendations.
I have a rolled gravel patio adjacent to a swimming pool. With a little two year old running around, I wanted to create a lawn for him.
Unfortunately, 10 cm below the gravel is a slab of concrete in which much of the pipework for the pool is buried (I believe). I've lifted about 4 tiles in various places to test and I keep coming up against the concrete each time. The good news is, I can raise the area by building a step down down to the pool.
I can probably build a 30 cm high retaining wall and fill with it with fresh soil, giving me around 25 cm of depth for the roots, accounting for the length of the grass having it roughly flush with the edge of wall. Do you think this would work? Should I be worried about anything? Should I put the soil directly onto the concrete or lay anything as a base layer?
I've read in some places that 20 cm should be adequate, but have seen others complaining about lawn failing to establish and dies off in the summer with a similar situation.
The garden is South West facing and gets a lot of sunshine. The property is in the French Alps and so gets a fair amount of snow in the winter in case either of this factors into the matter.
Thanks for any help or suggestions.