Every Water Formula calculation begins with the building's facing direction (面向, mian xiang) — and getting this wrong invalidates everything downstream. Modern architecture, urban density, and the rise of apartment buildings have made facing identification harder than it was for classical detached houses. This guide gives a practical method that handles the common edge cases.
The classical rule: yang side = facing
Classically, a building "faces" its yang side — the side with more light, more activity, more openings, more visible street frontage. The opposite side is the "sitting" side — the more solid, enclosed, often back-of-property side. For a typical detached house with a clear front door on the road and a back garden away from the road, facing is unambiguous: it is the front door direction. The Water Formula calculation uses this facing direction as the input axis for all subsequent direction lookups.
Modern apartment buildings
For apartments, two distinct facing directions matter: the BUILDING's facing (the lobby's main entrance from the street — what the entire structure faces) and the UNIT's facing (your specific apartment's main window or balcony orientation). For Water Formula analysis of your unit, use the unit-level facing. For analysis of building-level features (lobby, parking entrance, communal water features), use the building-level facing. This distinction is the most common source of error in audits of apartment-dwellers — practitioners new to the system often default to building-level for everything, which produces consistently wrong remediation prescriptions.
Edge cases: corner units, glass-walled offices, and dual-frontage shops
Corner apartments with windows on two facades: facing is the side with the larger window area or the side overlooking the more active street. Glass-walled modern offices: the facing direction is the wall with the primary entrance, NOT the wall with the most glass — in offices, the door dominates over the window. Shops with two equal frontages (e.g., on a corner with displays on both sides): the facing is the side with the cash register or primary customer-service interaction, because that is where the energetic activity concentrates. When in doubt, the test is "where does the most foot traffic actually enter and exit?" — that direction is the true facing regardless of the architectural diagram.