How are buildings lit?
A light on the highest point, lights along the roof edges, and every light kept clear of parapets and plant so it can be seen from all sides.
A building is an obstacle for aircraft only when it is tall enough, or close enough to an aerodrome, to stand above or near the protected airspace. Where the regulator decides it must be lit, it is lit like any other fixed object: the light class follows the height, from fixed red low-intensity lights on lower buildings to medium-intensity lights on taller ones.
A light goes on the highest point, which on a building is often rooftop plant, a lift overrun, a water tank or an antenna. More lights go on the roof corners and edges so the extent of the building is clear, spaced along a wide roof within the limit for the light type. A tall building adds mid-level lights, spaced as equally as practicable down the sides.
What is different about a building is its setting. It stands in a city full of other lights, and its own parapets and roof clutter can hide a light from low angles. Lights are therefore set clear of and above them. A lower building beside a taller lit one may need no light at all if the study finds it is shielded.
| Part | Treatment | Notes |
|---|---|---|
| Highest point | Light on the top | Whichever item is highest: roof plant, lift overrun, tank or antenna |
| Roof corners and edges | Show the extent | Lights at the corners, and the edge nearest the aerodrome where edges are at the same height |
| Wide roof | Limited spacing | Further lights along the edges; about 45 m apart at most for low-intensity lights, with the limit set by the light type |
| Tall sides | Mid levels | Intermediate tiers spaced as equally as practicable where the height calls for them |
| Parapets and plant | Clear view | Lights stand above or clear of anything that could hide them, with an extra light where one is shielded |
| Lower or shielded building | May need none | Where the study finds a taller lit object shields it. The regulator decides |
| Day | Marking or white lights | Large unbroken surfaces may call for a checkered pattern; white lights flashing by day can replace marking where the regulator allows |
| Building height | Light class | Where the lights go | Notes |
|---|---|---|---|
| Under about 45 m | Fixed red | Highest point and roof corners and edges | Low-intensity Type A or B. Often the whole answer for a lower building that needs a light at all |
| About 45 m to 150 m | Flashing whiteFlashing redFixed red | Top, roof edges and mid levels | Red types are used with day marking. Type A also works by day |
| Above about 150 m | Flashing white | Top, with mid tiers to keep the gaps within the limit | High-intensity, stepped down at twilight and night. Glare is a concern in a city, and care is needed near an aerodrome |
Check it is an obstacle
Compare its height and position with the protected airspace around the aerodrome. Many buildings are not obstacles and need no light.
Light the highest point
Fit the top light on the highest part, plant and antennas included, so the full height of the building is shown.
Mark the roof edges
Add lights at the corners and along the edges, at equal spacing within the limit for the light type, so the extent is clear.
Add levels, keep clear
On a tall building add mid levels, and place every light clear of parapets and plant so it is seen from every direction.
City backdrop
Obstacle lights compete with facade, signage and street lighting, so they must stay recognisable and separate from decorative light.
Roof clutter
Parapets, plant, tanks and antennas can hide a light, so lights go on the highest items and clear of anything that shields them.
Access to maintain
Roof lights must be reached safely to change a lamp or lens. Fit them where they can be serviced, with guarded access and fall protection.
Power and alarms
The lights need a reliable supply, usually with a standby source, and a way to raise an alarm when a light fails.
Three kinds of light on a building are easily confused:
- Obstacle Lighting→ the aviation lights that show the building to pilots, at night and, for white lights, by day
- Facade and Architectural Lighting→ decorative or advertising light, which is not an aviation signal and must not be mistaken for one or dazzle pilots
- Rooftop Heliport Lighting→ a separate set of lights for a helipad on the roof, with its own rules
Also note that height alone does not decide it. The same building may need lights beside an airport and none in a city centre well away from any flight path.
ICAO Building Obstruction Lighting
ICAO Annex 14 Volume I, Chapter 6, treats a building as a fixed object. The light class follows the height, from fixed red low-intensity lights on lower objects to medium-intensity lights from about 45 m and high-intensity lights above about 150 m. One or more lights are placed as close as practicable to the top, arranged to show at least the points or edges of the object that are highest in relation to the obstacle limitation surface. Where two or more edges are at the same height, the edge nearest the aerodrome is included, and on an extensive object the lights show its general extent. Which objects count as obstacles at all, including shielding by an existing object, is covered in Chapter 4 of the same Annex. Take the light types, number and layout from the regulator's determination and the current edition of the standard.
FAA Building Obstruction Lighting
The FAA covers structures in AC 70/7460-1, Obstruction Marking and Lighting, and a building is judged through the FAA notice and determination process. Where lighting is required, the styles use fixtures such as the L-810 (steady red), L-864 (flashing red), L-865 (flashing white, medium intensity) and L-856 (flashing white, high intensity). The number of light levels and the placement at each level follow the height of the building and the determination. Confirm the current edition of the advisory circular, the lighting style the FAA determination requires for your building, and any local rules on facade lighting.
Frequently Asked Questions
Q1Do all buildings need obstruction lights?
No. A building needs lights only when the regulator's study finds it is an obstacle, because it stands above or near the protected airspace around an aerodrome or its flight paths. Most buildings are well clear of it, and a lower building beside a taller lit one may be treated as shielded. The decision comes from the aeronautical study, not from height alone.
Q2Where are obstruction lights placed on a building?
On the highest point, including rooftop plant, lift overruns, water tanks and antennas, and along the roof corners and edges so the full extent of the building is clear from every direction. On a tall building further lights are added at mid levels, spaced as equally as practicable. The exact arrangement comes from the regulator's determination.
Q3Why are roof lights set above the parapet?
A parapet, plant room or tank can hide a light from low angles, which is where a pilot normally sees it. Lights are placed clear of and above these items so they can be seen from every direction in azimuth, and an extra light is added where one would be shielded.
Q4Can decorative or facade lighting replace obstruction lights?
No. Decorative light is not an aviation signal and does not stand in for obstacle lights. It can also confuse or dazzle pilots, which is why non-aeronautical lights near an aerodrome are controlled. Keep facade lighting separate and check that it neither hides nor mimics the red obstacle lights.
Q5Who decides whether a building needs lights?
The aviation regulator, through an aeronautical study or height-clearance process. In the US that is the FAA notice and determination process, and in India it is the AAI height-clearance (NOC) process for buildings near airports. The result sets whether lights are needed and their type, number and positions, so take it from the determination for your building.
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