Opening windows are often fitted with restrictors to limit opening. To comply with the requirement for restrictors in BS EN 14351-1, window restrictors are required to ‘hold the leaf, casement or sash in place for 60 s when 350 N are applied to the leaf, casement or sash in the most unfavourable way (i.e. position, direction).’
BS 6375-2:2009 requires safety devices, where fitted, to meet the requirements of BS EN 14351. The earlier 1987 version of BS 6375-2 required restrictors to resist a force of 600N.
BS EN 13126-5 also requires safety restrictors to be able to restrict the opening of a window to 100 mm under a force of 350N, but child safety restrictors are required to limit the opening to 89mm under a force of 500N.
Window restrictors are normally used to restrict opening of windows above barrier height. Where opening windows extend below barrier height and are not protected by a separate barrier, restrictors are required to limit opening under the barrier loads given in BS 6180.
Due to the complex interaction between all the components that make up the window, testing may be the most reasonable way of demonstrating performance, even when standard restrictors are used.
There have been a number of incidents where occupants of health and social care buildings have been able to overcome restrictors leading to fatal falls. Occupants of such buildings may be in a confused mental state and restrictors may be required to resist deliberate attempts to overcome them rather than normal day-to-day forces. This is not currently considered in the available standards.
HSE report RR1150 provides a review of the use of window restrictors in health and social care buildings and has recommended that restrictors in such premises should be designed to restrict window opening under a static push force of at least 850N. It is recognised that greater forces may be applied as a result different methods of attack including impact and where there is a risk of such action consideration should be given to the appropriate level of protection on a case-by-case basis.
A coroner’s prevention of future deaths report has recently drawn attention to this issue and in response it is proposed to amend BS 6375-2 to include reference to the 850N force for buildings where vulnerable people are present.
This action does not address the possibility of disengaging the restrictor other than by excessive force on the sash or casement and the standards referred to above do not make specific reference to disengagement of restrictors. BS EN 13126-5 includes tests for some aspects that relate to disengagement of restrictors such as cutting resistance of wire restrictors. BS 8213-4 has a requirement that safety restrictors are releasable ‘only by manipulation not normally possible by a child under 5 years’.
It should be noted that restrictors are required to resist a static force. If windows are left open, they may be subject to repeated dynamic loads as a result of wind action for which they are not designed.
Therefore, consideration must be given to ensuring that the window is closed during extreme weather events if following BS EN 14351-1. If this cannot be controlled adequately, consideration could be given to providing restrictors/stays or other components that can withstand the expected wind loading in the accidental conditions in which windows are left open during storms or high wind conditions or alternative opening configurations such as sliders, open in etc. The use of open out windows should be considered thoroughly and a detailed risk assessment produced to mitigate all reasonably practicable risks.
Read more about the use of outward opening windows here.
References
BS EN 14351-1:2006+A2:2016 Windows and doors. Product standard, performance characteristics. Windows and external pedestrian doorsets.
BS 6375-2:2009 Performance of windows and doors-Part 2 Classification for operation and strength characteristics and guidance on selection and specification.
BS 6375-2:1987 Performance of windows. Specification for operation and strength characteristics.
BS EN 13126-5:2011 +A1:2014 Building hardware. Hardware for windows and door height windows. Requirements and test methods. Devices that restrict the opening of windows and door height windows.
BS 8213-1:2004 Windows doors and rooflights. Design for safety in use and during cleaning of windows, including door-height windows and roof windows. Code of practice.
HSE RR1150 Review of window restrictors used in health and social care, 2019
Terrence Taylor: prevention of future deaths report 2024-0336
Harry Simpson - May 02, 2025
Many of the risks highlighted here are just as relevant to typical residential buildings. In practice, we often find window restrictors have been tampered with or removed — usually in an effort to improve ventilation, or simply because the occupant isn’t aware of the potential safety implications.
The challenges in health and social care settings are well understood, and in those environments, it’s sensible to increase the required static push force for restrictors. There are also several types of restrictors on the market, including key-operated versions, which help prevent deliberate interference — and could be more widely considered in high-risk scenarios. At the same time, we should be reviewing window configurations themselves and how can we better balance ventilation, durability, and safety in the design stage.
More broadly, the misuse of windows and their restrictors or stays remains a common issue — often driven by poor communication between key parties, including the supplier, installer, principal contractor, building management, and ultimately, the end user, in a lot of cases residents are rarely provided with clear operational guidance, despite being the ones ultimately responsible for using these windows safely. The Operation and Maintenance Manual should provide all of the relevant information regarding maintaining the building, but I question how well this is being translated to the end user.
Building management companies also have a duty here. Regular inspection and testing of restrictors should form part of routine maintenance to ensure they’re in good working condition, but also to check for signs of tampering or misuse.
Ultimately, it all comes back to communication. In the not to distant future I’m sure there will be smarter ways involving technology to monitor the condition of window restrictors and even alert or intervene when they’re tampered with or damaged!