Understanding Window Fall Prevention Requirements for Child Safety

The window fall prevention requirements in Section 9.8.8.1.(4) of the National Building Code apply to openable windows in dwelling units that are located more than 1800mm (approximately 6 feet) above the adjacent ground level or floor below. This typically means windows on the second floor or higher of residential or mixed-use buildings, though it can also apply to first-floor windows in homes with walkout basements, elevated foundations, or significant grade changes. Windows below this 1800mm threshold—such as typical first-floor windows at grade level—are exempt from these specific fall prevention requirements. The regulation targets locations where a fall could result in serious injury or death. The requirement reflects reported cases of small children falling from windows and is designed to prevent these tragic accidents by establishing clear safety standards for window design and installation.

According to NBC Sentence 9.8.8.1.(5), openable windows subject to this requirement (those more than 1800mm above ground or the floor below) must have their openable portion positioned at a minimum height of 900mm (approximately 3 feet) above the floor. This critical measurement corresponds to the minimum height of guards required by Sentence 9.8.8.3.(2) as a means of fall protection in residential occupancies. The regulation is based on extensive safety research showing that this height prevents young children from climbing up and accidentally falling through or out of windows. This requirement applies to all operable windows in dwelling units where children might be present, including bedrooms, playrooms, and common areas on elevated floors—provided those windows are more than 1800mm (6 feet) above the ground or floor below.

The 100mm (approximately 4 inches) opening limit stated in Sentence 9.8.8.1.(4) is recognized as the maximum opening size required to protect small children from falling through open windows. This precise measurement ensures that even if a child can reach a window, they cannot fit through the opening. The requirement will primarily impact the use of sliding windows which do not incorporate devices in their construction that can be used to limit the openable area of the window. When windows are designed with this limited opening, they provide ventilation while maintaining critical safety protection.

Care must be taken when selecting windows, as some with special operating hardware can still be opened further by simply pushing on the window or by deactivating a spring-loaded button or other mechanism. True Window Opening Control Devices (WOCDs) cannot be inadvertently operated by a young child. A technical description of WOCDs can be found in ASTM F2090, 'Standard Specification for Window Fall Prevention Devices With Emergency Escape (Egress) Release Mechanisms.'

Examples of mechanisms that can limit window openings to a maximum of 100mm as required by Clause 9.8.8.1.(4)(b) include, but are not limited to: • Fixed-stop lever • Fixed-length cable • Fixed-position stop block

These devices must be permanently integrated into the window design and cannot be easily bypassed by a child.

It is important to note that rotary opening mechanisms (such as casement windows with cranks) cannot limit window openings to 100mm as required by Clause 9.8.8.1.(4)(b), and windows with such mechanisms cannot act as guards as required by Clause 9.8.8.1.(4)(a), even when the crank handle is removed. Once cracked open, these windows can be opened further by simply pushing on the openable part of the window.

Similarly, awning windows with scissor hardware may not keep the window from swinging open once it is unlatched. Hopper windows would be affected only if an opening is created at the bottom as well as at the top of the window.

These limitations must be carefully considered during the design and specification phase to ensure code compliance and child safety.

While the 900mm height requirement and 100mm opening limit are the standards, the building code recognizes that architectural design sometimes requires alternative solutions. In these cases, there are approved alternatives that provide equivalent safety protection:

1. Windows Acting as Guards: Windows that meet the requirements of Clause 9.8.8.1.(4)(a) can function as guards themselves when properly designed and installed.

2. Limited Opening Windows: Install windows with approved opening restrictors that prevent the window from opening more than 100mm using fixed-stop levers, fixed-length cables, or fixed-position stop blocks.

3. Fixed (Non-Operable) Windows: Make the window permanently fixed so it cannot be opened at all, eliminating the fall risk entirely.

These alternatives must be carefully planned during the design phase and properly implemented during construction to ensure they meet code requirements.

For builders and contractors, ensuring compliance starts at the design stage. Window schedules should clearly indicate sill heights, window types, and any opening control devices being employed. Rough openings must be framed accordingly, and window opening control devices must be specified from manufacturers that meet ASTM F2090 standards.

During framing inspection, building officials will verify that window openings meet the required heights or that appropriate alternative measures are in place. Special attention should be paid to window types—avoid specifying casement windows with rotary mechanisms or awning windows with scissor hardware in locations where fall prevention is required, as these cannot meet the 100mm opening limit.

If you're working on a renovation or addition, pay special attention to this requirement—many older homes don't meet current standards, and any new construction must comply with today's codes.

If you're building a new home or planning a renovation, discuss window placement and types with your builder early in the design process. While high windows or limited openings might seem inconvenient, remember that this is a life-saving measure based on real reported cases of child injuries and fatalities.

For existing homes with windows that don't meet current standards, consider retrofitting with approved window opening control devices that limit the opening to 100mm. However, be aware that not all aftermarket devices meet the stringent requirements of ASTM F2090—they must not be easily deactivated by a young child.

Avoid relying on removable crank handles or spring-loaded buttons as safety devices, as these can be inadvertently operated by children. Instead, look for fixed-stop mechanisms that are permanently integrated into the window design. Make sure any devices you install meet current building code standards and cannot be bypassed by simply pushing on the window.