My figures are for hobby keeping.
In the industrial keeping, but also in the targeted breed other sizes and types of keeping are considered acceptable.
For each barn / aviary (whether indoor or outdoor ) should be that the quail dry and drafts must be freely placed as security against predators , even against the digging through (Rats, weasels), must be guaranteed .
The minimum size for a room should not be less than 2 qm . On this surface, a group of 1.5 ( on a rooster 5 hens) are well kept.
More important than the size, ist the structure of the housing. What is present at hiding? How do I bid on water and food? What is the sand bath? What bedding do I have? (important for the cleaning interval)
First, you should consider how many quail you want to keep :
I personally prefer the aviary. This has several advantages for me :
Here are a few pictures of my aviary.