What is a building standards act?
It is the main law that sets the minimum standard for every building: how strong it must be, how safe from fire and how healthy to live in. The same code also decides how buildings fit into a town. It has two parts: building-level and city-level provisions.
Building-level provisions (rules inside one building)
These rules are about the building itself, wherever it stands.
- Structure: columns, beams and foundations must bear the loads, wind and earthquake forces.
- Fire safety: fire-resistant materials, alarms, at least two ways out in bigger buildings, fire doors.
- Sanitation and health: clean water, drains, toilets, enough window area for light and fresh air.
- Materials: they must meet quality standards.
City-level provisions: coverage and floor area ratio
These rules are about how a plot fits into the town, so everyone gets light, air and open space.
Coverage ratio = footprint (ground area covered) ÷ plot area × 100 %.
Floor area ratio (FAR) = total floor area of all floors ÷ plot area × 100 %.
Example: plot 200 m², footprint 90 m², 3 floors. Coverage = 90 ÷ 200 = 45 %. Total floor = 270 m², so FAR = 135 %.
City-level provisions: roads, gaps and height
A building must face a road of a minimum width, so fire engines and ambulances can reach it. It must keep a gap (setback) from the road and from the neighbour. Many cities also limit height, often with a sloping line from the road, so the street and the neighbours still get sky and sun. Each city sets its own numbers, within the national law.
Key formulas and definitions
- Coverage ratio = footprint ÷ plot area × 100 %
- Floor area ratio (FAR) = total floor area ÷ plot area × 100 %
- Total floor area = footprint × number of floors (if all floors are equal)
- Gap from the road ≥ minimum setback
Worked examples
1. Plot 200 m², footprint 90 m². Find the coverage ratio.
Coverage = 90 ÷ 200 × 100 = 45 %.
2. The same plot has 3 equal floors of 90 m² each. Find the FAR.
Total floor = 3 × 90 = 270 m². FAR = 270 ÷ 200 × 100 = 135 %.
3. A city allows coverage 60 % and FAR 200 % on a 150 m² plot. What is the largest footprint, and how many full floors can that footprint have?
Footprint ≤ 0.60 × 150 = 90 m². Total floor ≤ 2.0 × 150 = 300 m². Floors = 300 ÷ 90 = 3.33, so 3 full floors.
4. A shop owner wants 4 floors on a 100 m² plot, footprint 60 m². Limits: coverage 60 %, FAR 200 %. Is it allowed?
Coverage = 60 %, ok. Total floor = 4 × 60 = 240 m², FAR = 240 %, more than 200 %. Not allowed. He can have at most 3 floors (180 %).
Common mistakes
- Mixing coverage and FAR. Coverage uses only the ground footprint; FAR adds all floors.
- Forgetting that FAR can be more than 100 %. A 3-storey building on a full-footprint plot has FAR 300 %.
- Thinking building-level rules depend on the town. They follow the building; city rules follow the plot and street.
- Counting the plot area from the road centre. Plot area is the owner's land only.