My mother in law does this. It's more the sand is the draining layer on bottom and everything is changed after a while (couple months or personal preference). It's pretty much the same as all the other deep litter methods with a little more drainage. The nest boxes have the mock astro turf pad...
sand and pine shaving .
Sand on bottom to improve drainage and pine shavings on top to prevent bumblefoot. The soft surface is what helps prevents it.
I wouldn't use it during the rainy season.
Gravel can be used under the sand but it can be risky if they eat it so I don't do it...
The risk with the straw is botulism. Straw / hay can grow mold after a while which if the hen eats certain types of mold it can lead to botulism. There is no cure and they either die from a slow painful death or I'd cull off the flock out of mercy.
Wood chips run the risk of the foot becoming...
Not if you get the rubbery grey nest pad. It's not rubber but it's more of that softer texture compared to orginal astro turf. There's different styles of astro turf. But yes it is astro turf with a lot of drainage. I also put a lot nesting material on top so they probably don't notice anything...
The astro turf helps prevent eggs breaking on hard surface and keep eggs somewhat cleaner
I too have this problem with sand and sometimes it's a constant rain... but when it;s not raining 2 weeks straight it's good.
I like to have a mix of litter for my deep litter but straw can get moldy and create a health risk to birds. Unless expertly maintained. Straw is most economical here tho ($6 organic straw vs $60 pine shavings for 1 month) so I go with regular method when more practical. Plus it rains a lot...