JOMY fire escape stairway dimensions


The responsibilities for fire evacuation are spread over many different levels, which make the matter quite complex. Depending on the specific situation, many different and sometimes conflicting conditions may apply. We will try to describe "the best practices" through all legal texts, standards, and technical specifications. These specifications must always be verified by the local authorities.


Evacuation Capacity

• The dimensioning of the fire escape stairway must correspond to the number of individuals to be evacuated. This number is determined by the surface area of the compartment as follows:

- 1 person per 10 m² for buildings that are not publicly accessible

- 1 person per 3 m² for buildings that are publicly accessible

- Exception if the fixed furniture provides another occupation


Number of Escape Routes

• Generally, there schould be at least two independent, non-intersecting escape routes. The recommendations vary depending on the capacity of the building.


• If there are 500 or more individuals, the recommandations are as follows
- 500 - 999 persons: 3 escape routes
- 1000 - 1999 persons: 4 escape routes
- 2000- 2999 persons: 5 escape routes

• There are case where a single fire escape route will suffice

- Buildings of less than 10m with fewer than 100 persons

- Buildings between 10m and 25m  and fewer than 50 persons with access for fire ladders on the street side


Even in these cases, the fire department often requires also a second escape route.

In general, the fire department can always ask additional escape routes.

Location of the Emergency Stairs


The escape stairways should go in opposite areas of the space. The maximum distance from the escape route to the stairway is fixed. Aside from technical areas, this is based on the use of the building, during the day or night.


   Use of the building  

Used during the Day

Also USed at Night
Distance to Path Connecting Two Stairways <= 30m
<= 20m
Distance to Closest Stair <= 45m
<= 30m
Distance to second Closest Stair <= 80m <= 60m

     - Maximum distance from a dead-end route is <= 15m


Access to Emergency Stairs

There are guidelines regulating emergency stairway access.

Through doors and hallways, the access door has to be Rf 1/2h for a building > 25m and the doors cannot be locked in the direction of the evacuation.

Counterbalanced flight or paneling/enclosure of the lower flight is allowed.

The stairs of buidlings > 25m must provide access to the roof (if roof is flat).


Usable Width (UW)


The usable width is determined by the largest number of persons to be evacuated. The sum of the UW of all descending stairs has to be at least equal to the number of persons to be evacuated from the largest compartment, multiplied by 1.25cm (ΣUW = number x 1.25cm


The minimum UW is 80cm, which corresponds to an evacuation of 64 persons (80/1.25). UWs can be seen in multiples of 60cm (the transit unit), as follows.


- UW of 80m for max 64 persons per compartment and per stair


- UW of 120m for 65 to 96 persons per compartment and per stair


- UW of 180m  for 97 to 144 persons per compartment and per stair


There are often exceptions to the rule.


- For medium and high buildings (> 10m, a minimum UW of 60cm can suffice (verify with authorized fire department).


- Depending on the available space and number of persons to be evacuated, UWs of 90cm, 101cm, and 110cm may be used.


- In schools and daycares, a UW of 120cm is provided, even when the number of persons to be evacuated is less than 64 per compartment.


Different stairs of the same compartment must have the same UW, plus or minus 60cm.


The value of 1.25cm per person applies with descending stairs. For rising stairs, 2cm per person is provided. For flat escape routes, the requirement is 1cm per person.



The stairs must be at least 1m away from the wall opening (with <= Rf 1h).

At least one side must permit the free flow of air.
Spiral stairs are generally discouraged and for tall buildings (>=25m ) even prohibited. A spiral stair must have a thread of at least 24cm on the walk line, located 0.4m to 0.6m from the handrail or the spindle and at least 0.35m from the outer edges of the steps.
Usually, an incline of 37° is requested (or about 75%).
For medium and high buildings (> 10m), an incline of 45° may be acceptable (confirm with authorized fire department). Sometimes, the stairs can only be used by persons with good mobility. For rising staircase, an incline of 45° is acceptable.
Inclines greater than 45° must be avoided.

The tread "a" and the riser "o" must meet the following formula: 600mm <= a + 2o <= 660mm.

Risers are not necessary.

A lower flight may have a maximum of 17 steps. If a greater height must be bridged, an intermediate landing must be provided.



Always provide two guardrails per staircase. 

- Exception: One guardrail is sufficient for stairs with UW < 120cm, low buildings (< 10m, and when there is no risk of falling.

The minimum height for escape stairs is 1m on the landings and 0.9m on the stair flights, measured on the stair nose.

When used by children (schools, nurseries, etc):

- The maximum gap between the vertical bars is < 80mm(< 70mm in Wallonia).

- No horizontal elements to avoid children using them as a step

- Height of 1.1m instead of 1m

- Second guardrail at the height of the children (below the main guardrail)



Materials must be of class A0 (non-flammable material, such as aluminum, steel, or concrete).

There are no fire resistant requirements for outdoor stairs.

Stable materials must be used that will not gradually deteriorate with age.


Stability requirements


The stairs must be able to carry a uniformly distributed load of 102 lb/ft² or 500 Kg/m² on each flight (the surface projected on the horizontal plane) and on the landings.


The stairs must support a point load of 200Kg applied anywhere on the steps or the landing deck, and the guardrails need to be able to withstand a horizontally applied uniform load of 100 Kg/m, without permanent deformation.




Cookies! Ce site utilise des cookies pour faciliter votre expérience de navigation et peut fonctionner moins bien si vous les désactivez. En naviguant sur notre site avec les cookies, vous acceptez leur utilisation.