They are commonly known as TMBs.
![Roof top structures](../../../../images/safety-and-inspection/ubw/06private_rooftop01.jpg)
Roof top structures
![Yard/private lane structures](../../../../images/safety-and-inspection/ubw/06private_rooftop02.jpg)
Yard/private lane structures
TMBs are building works outside a building, carried out without the prior approval and consent of Building Authority. They may:
- constitute structural risks. There have been cases where TMBs have collapsed, resulting in tragic loss of lives.
- constitute fire risks.
- obstruct fire escape routes that may lead to great casualties in case of fire.
- constitute health nuisance or lead to deterioration of the environment by accumulation of rubbish on UBWs and unpleasant appearance of UBWs.
- obstruct the day-to-day maintenance as well as major repairs to a building.
![](../../../../images/safety-and-inspection/ubw/06private_rooftop03.jpg)
Flat roof structures
Flat roof structures and yard/private lane structure may also cause obstruction to light and air.
See also