Fire breaks: compliance with calculation standards

Fire gap is the distance between buildings and structures, which is determined by the norms. Their presence and size must be taken into account in construction, in particular when designing. The main function of fire breaks is to prevent the spread of fire between buildings. They are also designed for her free maneuver. At the design stage, the placement and calculation of gaps is closely related to the requirements of sanitary and hygienic standards.

Laws, regulations and norms

The first document that should be consulted before starting and during the design is SNiP 2.07.01 - 89. It contains a mandatory supplement with fire requirements, which indicates the parameters for calculating the optimal fire distance between buildings. To calculate the distances in the territories where the warehouses and storages of oil products are located, refer to SNiP II-106-79.

The Federal Law "Technical Regulations on Fire Safety Requirements" defines the responsibility of the owner of a building or structure in its scope. This means that the rightful owner is obliged to ensure fire safety at any facility that belongs to him. This is confirmed by the declaration. The protection of an object consists in the presence of a security system, including the presence of breaks, as one of the types of fire barriers.

This Federal Law gives definitions to the official terms of this subject and distributes the effect of normative legal acts. Some of them may be optional. For example, several sets of rules can be neglected. However, in order for deviations from any norms to be not criminal, it is necessary to provide a base of evidence that such a move does not contradict the legislation and has the right to exist.

In SNiP 21.01-97, you can see the classification of buildings and structures based on the degree of fire resistance. The assignment to a specific class depends on the fire resistance of the structural elements. Functional fire hazards are described there. Both classifications are important when calculating gaps. The set of rules 4.13130.2013 was created with the aim of establishing a sufficient level of safety in the design, as well as reconstruction of buildings with certain parameters. It contains clarifications and tables with values and assumes taking into account the peculiarities of production in buildings, is directly related to the federal law on fire safety and state standards.

Required characteristics

Now is the time to look directly at some of the characteristics of fire breaks.

First of all, there should be enough space between the buildings for the full operation of fire engines and equipment. If there are individual structural elements made of combustible materials on the facade of a building, and they protrude more than 1 meter, then the distance is measured from their extreme point.

In practice, the distance between the outer walls is approximately 6-10 meters, and for buildings made of wood and materials with similar fire-resistant characteristics, it is about 15 meters. There are calculation methods, but sometimes it is allowed to reduce the gap in the following cases:

in the presence of a fire wall or other barrier made of fire-resistant materials;
with the installed alarm, fire extinguishing system;
in the absence of window openings in the building up to IIIA degree of fire resistance.

Increase the distance between such buildings:

in areas with increased seismological activity;
made of a frame or covered with combustible materials of the V degree of fire resistance;
located on a coastline 100 kilometers wide if the mountain range is not in this area.

Clarifications for each item are posted in SNiP 2.07.01–89. In addition, for residential buildings and outbuildings on the same site, the rationing of distances is not provided for by fire safety standards. Here it is appropriate to be guided by the values established by the sanitary-hygienic and insolation standards. A similar approach when calculating gaps is used when the total area of buildings and the distances between them does not exceed the area that can be fully used by one object.

Business buildings can be built at any distance from neighboring ones, provided that the total area of the grouped objects is less than 800 square meters.

Separate requirements are intended for the installation of small retail pavilions and frame structures. Temporary structures are located near fire walls or at a distance of at least 15 meters from other buildings. The use of fire-prevention distances is prohibited for placing on them a warehouse of products, obstructions and long-term parking of vehicles.

Principle and calculation formula

Several factors influence the final values for calculating fire clearances between buildings. Initially, the fire resistance class of the building is established according to the rules, and then the constructive fire safety is determined. The more fire-resistant a building is, the larger the gap will be.

Functional safety plays an important role in the calculations. So, in production halls, fire risks are much higher in relation to public buildings or private houses. The cause of a fire can be a spark resulting from the operation of technological equipment or power tools.

The general values are indicated in the current rules and codes, but you can find out the distance and justify it as part of the calculation of fire risks, during which the measure of the possible fire hazard and its consequences for people and property is revealed. Calculation of fire risks is carried out in case of deliberate non-compliance with the requirements of standards and rules in terms of fire safety.

Key values in the formula for calculating ruptures are the amount of heat flux in case of a fire (possible), the intensity and duration of irradiation of adjacent buildings and the time until the arrival of fire brigades. In this case, the first value should not exceed the minimum irradiation intensity if the duration of irradiation and the time of arrival of firefighters are the same.

In the variant with a simulated fire inside and between neighboring buildings, the existing gap, the characteristics of the fire (flame) and irradiation are taken as the initial data. For this method, a special formula is used, the irradiance coefficients. The construction of a function (nomogram) without calculations will help to achieve the correct result. The dependence of the distances on the initial data (characteristics of the flame, the intensity of irradiation and the ratio of additional parameters) is investigated. Such characteristics of the flame as the temperature is considered the same over the entire surface, as well as the degree of fire resistance of all buildings. The calculation will turn out to be correct if there is a reasonable dependence and the influence of the parameters on the result or equality is correct.