When we lived in California my Husband made a "kitty cage". It was framed to about 8'x8'x4'tall. We stapled chicken wire to it and loosely attached it to the side of the house. I could open a bedroom window to allow them outside for freshair, sunshine and outdoor visual and olfactory stimulation. If I wanted them inside, I placed a lawn sprinkler near the 'kitty cage' and turned it on. Came in the house and shut the window and then turned off the sprinkler.
It did take me a while before I knew how far to turn the spigot to reach all corners of the cat cage but not reach the bed inside the window. 0_o My major problem, was flies, because the screen had to be removed to give the cats access.
We are in a different house now, and we are thinking of enclosing a covered patio outside the kitchen french doors. Maybe installing a cat-flap in the wall to give them at-will access. Currently, I am using a wire dog crate. It is about 3'x4'x4'tall. We've put a few 2x12 boards across at different heights for them to perch on, food/water at one level and a litterbox on the bottom. This requires us to take the cat(s) out there and bring them back inside. I would prefer they be able to do it themselves, so that is why we are looking at enclosing the back patio.
Is your house situated in such a manner as to be able to attach a large wire dog-run to the house and give the cats access through a permanant cat-flap?
Below is a link that has good examples of the type of 'kennels' I mean. You can make them yourselves with a wood or pipe frame and attaching mesh wire to it.
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http://www.cats-on-line.com/catcagesbronzeplus.htm