How much room do cats need??

So we are getting a cat or two.
So as I don't like cat boxes inside the house we need to do some sort of run outside.
So how much room is needed?
My local M10 says to get an aviary or small chook house because if it says "CAT" in the description it costs more LOL
Looking at the smallest Cecile thinks they are too small, I disagree and google just adds to the confusion. Cat people say cats need more room than "Non-Cat" folks but costs triple when you get into the larger sizes.
Please help us find some sort of consensus on a reasonable outside box.
This must be the third of fifth time we have asked and I'm no clearer


Read the full thread at RenovateForum.com...