Short answer: a dry room where the floor itself is kind
Site a Rex rabbit's cage in a dry, draught-free room — a calm sitting room or spare bedroom — on a solid surface you can cover deeply with bedding. The Rex's velvet coat is the breed's glory, but the short fur on the underside of her feet cushions her hocks poorly, and a cage standing on cold concrete, in a damp corner or on a surface that stays wet under the water bottle makes sore hocks far more likely. This placement decision is partly a foot-health decision.
Why garages and utility rooms fail this breed
Garages, porches and laundry rooms are tempting for a bulky cage, but they combine the Rex's three enemies: cold rising from concrete, damp air that keeps bedding from drying, and temperature swings when doors open to the outside. Sore, thinning fur on the hocks can break into sore skin in those conditions before you notice, because a Rex's dense coat hides early redness. An indoor room with normal household heating keeps bedding dry and puts her where daily foot checks happen naturally during feeding.
Social, but not in the thick of it
A Rex is generally a sociable, good-natured rabbit who enjoys being near the family, so a lived-in room beats an empty one. Choose the quieter end — not beside a games console, not in the path between sofa and kitchen — and back the cage against a wall so she has a sheltered side. Keep her away from kitchen steam and cleaning sprays, and out of the patch of sun that moves across a south-facing floor, since a rabbit cannot leave a cage that is warming up.
Flooring, bedding depth and daily checks
Inside the cage, a solid floor with a generous depth of soft bedding matters more than the room's décor; wire floors are unsuitable for this breed. From her room placement, you also want good light for you — checking hocks means lifting each hind foot and parting that plush fur, and a dim corner makes the job cursory. A spot near where the family sits in the evening, with a lamp nearby, quietly guarantees those checks happen.
Think about humidity as well as visible damp. A room can look dry while a cage tucked behind a sofa against an outside wall sits in the coldest, dampest air in the house, where condensation gathers overnight. Pull the cage a few inches off that wall, keep air moving gently around it, and check the bedding at the back corners with your hand each morning for a week — it should feel dry and loose, not cool and clumped. For a Rex, that back-corner check is an early-warning system for her feet.
Reading whether the spot suits her
A settled Rex stretches out on her side, eats hay steadily and shows clean, fully furred hocks week after week. Restlessness, stamping at night or thinning fur on the feet are prompts to look at the surface and the room, not just the rabbit. On KinsLe, Family Sharing keeps her bedding changes, foot checks and feeding notes on a shared profile, so anyone in the household can spot a change and act on the same information.