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The buns live in a 7'x 5' shed, with an attached 8'x 3'run.
The shed is custom built with several levels, including a bedroom area (insulated with bubble wrap between the hardboard skins) and a hay rack.
The floor and levels are covered with lino for easy cleaning and to prevent rot. The edges of the lino are covered with wooden battens so the buns don't chew on it. All mesh panels are removable for easy cleaning.
The shed is fully insulated with 1" expanded polystyrene all around, to keep is warm in the winter and cool in the summer. The polystyrene is covered with hardboard where the buns can access to prevent them chewing it.
Mains power supplies light and a fan in the summer, or greenhouse heater in the winter to keep it above freezing. All electrical stuff is beyond access of the buns.
The run is contructed with thick gauge welded mesh for strength, again with all panels removable for cleaning.
Access to the run is via an old industrial heating pipe which the buns love as it is similar to a proper burrow entrance.