Before proceeding with the design, detailed planning requirements of the facility must first be ascertained. The first consideration must be given to the layout of the stalls. For design purposes a 12 by 12 ft stall may be considered a suitable size. This size will comfortably house a 16.0-17.0 hh horse. The basic layout of the buildings containing the stalls will depend on economic considerations as well as on site conditions. The simplest layout of stalls is a line opening directly into the open air. This is the simplest form of layout, and presents multiple variations in layout which can be derived from the basic in-line stall configuration. Depending on the number of stall needed they can be arranged around a yard, the roof structure can be extended along the open side to provide protection from the weather for the horses and grooms. The open side may be enclosed to provide better control of ventilation and draughts, provide improved working conditions, easier maintenance, and a quieter environment. The number of horses can be greatly increased by adding additional stalls to create a central passage.