I have transformed one downstairs bedroom into an aviary. Seven parrots happily reside inside; 4 Goffins, 1 Moluccan, 1 Citron, and one Timneh Grey.
The tile floor is completely covered with a layer of thick (6 mil) painters plastic that is changed about 3 times per year. Strategic sections are covered with another layer of 2 mil painters plastic and changed weekly. There are several cages that are normally opened; some birds are never permanently caged while some are "rotated" due to bullying issues against one Goffin. At times 6 are free to roam/fly around, while 4 are free about half the time. While some will argue against, these combinations are left alone for periods of the day with no problems. Many of the cages have locks destroyed by the "Houdini" cockatoos! A large central playpen is often the focal point for several birds. The only loner is the Timneh who wants nothing to do with the cockatoos. All of the food/water/treats are co-mingled and there are almost never territorial squabbles.
The flooring plastic is hung from a balcony and aired out for about 36 hours to help "out gas." Illumination is via window and overhead full-spectrum lighting. The stock door to the house has been augmented with a storm-door with lower glass and an upper screen for ventilation.
Overall this is a great solution and the birds seem happy with relative freedom.
