Similar questions have come up over and over again. I keep an extract from the Soviet norms
IIIa from SNiP 2.01.02-85* APPENDIX 2 Reference
EXAMPLE STRUCTURAL CHARACTERISTICS OF BUILDINGS
DEPENDING ON THEIR DEGREE OF FIRE RESISTANCE
1. Degree of fire resistance
2. Structural features

I
Buildings with load-bearing and enclosing structures made of natural or artificial stone materials, concrete or reinforced concrete using sheet and slab non-combustible materials

II
Same. It is allowed to use unprotected steel structures in the coatings of buildings

III
Buildings with load-bearing and enclosing structures made of natural or artificial stone materials, concrete or reinforced concrete. For floors, it is allowed to use wooden structures protected by plaster or slow-burning sheet, as well as board materials. There are no requirements for fire resistance limits and fire propagation limits for roofing elements, while attic wood roofing elements are subjected to fire retardant treatment.

IIIa
Buildings are predominantly with a frame structural scheme. Frame elements - from steel unprotected structures. Enclosing structures - from profiled steel sheets or other non-combustible sheet materials with slow-burning insulation

IIIb
The buildings are predominantly one-storey with a frame structural scheme. Frame elements - from solid or glued wood, subjected to fire retardant treatment, providing the required fire spread limit. Enclosing structures - from panels or element-by-element assembly, made using wood or materials based on it. Wood and other combustible materials of building envelopes must be subjected to fire retardant treatment or protected from the effects of fire and high temperatures in such a way as to ensure the required limit of the spread of fire.

IV
Buildings with load-bearing and enclosing structures made of solid or glued wood and other combustible or slow-burning materials, protected from fire and high temperatures by plaster or other sheet or plate materials. There are no requirements for fire resistance limits and fire propagation limits for roofing elements, while attic wood roofing elements are subjected to fire retardant treatment.

IVa
The buildings are predominantly one-storey with a frame structural scheme. Frame elements - from steel unprotected structures. Enclosing structures - from profiled steel sheets or other non-combustible materials with combustible insulation

V
Buildings, for the bearing and enclosing structures of which there are no requirements for fire resistance limits and limits for the spread of fire

Note. The building structures of buildings given in this appendix must meet the requirements of Table. 1 and other norms of this SNiP.

The most high degree fire resistance I (mausoleum).

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CODE OF RULES FOR THE FIRE PROTECTION SYSTEM - ENSURING THE FIRE RESISTANCE OF PROTECTION OBJECTS - SP 2-13130-2009 (approved by Order of the Ministry of Emergency Situations of the Russian Federation dated ... Relevant in 2018

6. Determination of the required degree of fire resistance of buildings, structures, structures, depending on their number of storeys, functional fire hazard class, fire compartment area and fire hazard occurring in them technological processes

The choice of the dimensions of the building and fire compartments should be made depending on the degree of their fire resistance, the class of constructive and functional fire hazard.

In case of combinations of these indicators not provided for in this section, the floor area and height of the building are taken according to the worst of these indicators for the building in question of the corresponding class of functional fire hazard, or special specifications In accordance with the requirements of Art. 78 N 123-FZ.

When designing, building, reconstructing, overhaul and technical re-equipment of facilities, in addition to the requirements of this Code of Rules, one should be guided by the provisions.

6.1. Industrial buildings

6.1.1. The degree of fire resistance, the class of constructive fire hazard, the height of buildings and floor area within the fire compartment for industrial buildings(class F5.1) should be taken according to Table 6.1.

Table 6.1

Category of buildings or fire compartments	Building height<*>, m	The degree of fire resistance of the building		Floor area, sq. m, within the fire compartment of buildings
				one-story	on two floors	three floors or more
A, B	36	I	C0	Not ogre.	5200	3500
BUT	36	II	C0	Not ogre.	5200	3500
	24	III	C0	7800	3500	2600
		IV	C0	3500	-	-
B	36	II	C0	Not ogre.	10400	7800
	24	III	C0	7800	3500	2600
		IV	C0	3500	-	-
IN	48	I, II	C0	Not ogre.	25000	10400
					7800 <**>	5200 <**>
	24	III	C0	25000	10400	5200
					5200 <**>	3600 <**>
	18	IV	C0, C1	25000	10400	-
	18	IV	C2, C3	2600	2000	-
	12	V	Not the norm.	1200	600 <***>	-
G	54	I, II	C0	Not limited
	36	III	C0	Not ogre.	25000	10400
	30	III	C1	Same	10400	7800
	24	IV	C0	-"-	10400	5200
	18	IV	C1	6500	5200	-
D	54	I, II	C0	Not limited
	36	III	C0	Not ogre.	50000	15000
	30	III	C1	Same	25000	10400
	24	IV	C0, C1	-"-	25000	7800
	18	IV	C2, C3	10400	7800	-
	12	V	Not the norm.	2600	1500	-
<*>The height of the building in this table is measured from the floor of the 1st floor to the ceiling of the upper floor, including the technical one; with a variable ceiling height, the average floor height is taken. The height of one-story buildings of fire hazard class C0 and C1 is not standardized.
<**>For woodworking industries.
<***>For sawmills with up to four frames, woodworking shops for primary wood processing and wood chipping stations.

6.1.2. The degree of fire resistance, the class of constructive fire hazard, the height of buildings and floor area within the fire compartment for livestock, poultry and fur-breeding buildings, the degree of fire resistance and floor area between fire walls should be taken from Table 6.2.

Table 6.2

	Production category	Allowed number of floors	Floor area between opposite walls of buildings, sq. m
			one-story	multi-storey
II	IN	9	Not limited	Not limited
III		3	3000	2000
IV		2	2000	1200
V		1	1200	-
II	D	Not limited	Not limited	Not limited
III		3	5200	3500
IV		2	3500	2000
V		1	2000	-

Building category	The degree of fire resistance of the building		Floor area, sq. m, within the fire compartment
IN	I, II, III	C0	9600
	IV	C0, C1	4800
	IV	C2, C3	2400
	V	Not the norm.	1200

Table 6.5

6.5.1. The permissible height of a building of class F1.3 and the floor area within the fire compartment should be determined depending on the degree of fire resistance and the class of constructive fire hazard according to table 6.8.

The degree of fire resistance of the building	Building constructive fire hazard class	The highest allowable height of the building, m	The largest allowable floor area of ​​the fire compartment, sq. m
I	C0	75	2500
II	C0	50	2500
	C1	28	2200
III	C0	28	1800
	C1	15	1800
	C0	5	1000
		3	1400
IV	C1	5	800
		3	1200
	C2	5	500
		3	900
V	Not standardized	5	500
		3	800

6.5.2. Buildings of I, II and III degrees of fire resistance can be built on one attic floor with load-bearing elements having a fire resistance rating of at least R 45 and fire hazard class K0, regardless of the height of the buildings specified in Table 6.8, but located no higher than 75 m. The enclosing structures of this floors must meet the requirements for the structures of the building being built on.

When using wooden structures, structural fire protection should be provided that ensures these requirements.

6.5.3. In buildings of I and II degrees of fire resistance, in order to ensure the required fire resistance limit of more than R 60 of the load-bearing elements of the building, it is allowed to use only structural fire protection (cladding, concrete, plaster, etc.).

6.5.4. The load-bearing elements of two-story buildings of the IV degree of fire resistance must have a fire resistance rating of at least R 30.

6.5.5. Fire hazard class and fire resistance limit of interior, including cabinet, collapsible, with doorways and sliding partitions are not standardized.

6.5.6. Public premises<1>should be separated from the premises of the residential part by fire partitions of the 1st type and ceilings of the 3rd type without openings, in buildings of the I degree of fire resistance - by ceilings of the 2nd type.

<1>Public premises - in this section - premises intended for the implementation of activities in them to serve the residents of the house, residents of the adjacent residential area, and others permitted for placement in residential buildings by the bodies of the State Sanitary and Epidemiological Supervision.

6.5.7. The load-bearing structures of the coating of the built-in-attached part must have a fire resistance rating of at least R 45 and a fire hazard class of K0. If there are windows in a residential building oriented to the built-in-attached part of the building, the level of the roof at the junction should not exceed the floor mark above the living quarters of the main part of the building. The insulation in the coating must be made of materials of the NG group.

6.5.8. Single-apartment residential buildings, including blocked ones (functional fire hazard class F1.4)

6.5.8.1. Blocked houses of constructive fire hazard classes C2 and C3 must additionally be divided by deaf fire walls of the 1st type and fire hazard class not lower than K0 into fire compartments with a floor area of ​​​​not more than 600 square meters. m, including one or more residential blocks.

6.5.8.2. Fire walls must cross all house structures made of combustible materials.

At the same time, fire walls of the 1st type, dividing the house into fire compartments, should rise above the roof and protrude beyond the outer wall cladding by at least 15 cm, and when used in the coating, with the exception of the roof, materials of combustibility groups G3 and G4 - rise above the roof by at least 60 cm and protrude beyond the outer surface of the wall by at least 30 cm.

The direct horizontal distance between any openings located in adjacent fire compartments must be at least 3 m, and in neighboring residential blocks - at least 1.2 m.

When adjoining the outer walls of adjacent fire compartments at an angle of 136 ° or less, the section outer wall forming this angle, overall length not less than 3 m for adjacent fire compartments must be made in such a way that it meets the requirements for the corresponding fire wall.

6.5.8.3. There are no requirements for fire resistance and constructive fire hazard class for houses up to two floors inclusive.

6.5.8.4. In houses with a height of 3 floors, the main structures must comply with the requirements for structures of buildings of the III degree of fire resistance: the fire resistance limit of load-bearing elements must be at least R 45, ceilings - REI 45, non-bearing external walls - RE 15, floorings of non-attic coverings - RE 15, open trusses, beams and girders of bare roofing - R 15. Fire resistance limit interior partitions not regulated. The structural fire hazard class of the house must be at least C2.

With floor area up to 150 sq. m, it is allowed to take the fire resistance limit of load-bearing elements at least R 30, ceilings - at least REI 30.

6.5.8.5. Houses with a height of 4 floors must be at least III degree of fire resistance and constructive fire hazard class at least C1.

6.5.8.6. The building structures of the house should not contribute to the latent spread of combustion. Voids in walls, partitions, ceilings and coatings, limited by materials of combustibility groups G3 and G4 and having minimum size more than 25 mm, as well as the sinuses of attics and attics should be divided by blind diaphragms into sections, the dimensions of which should be limited by the contour of the enclosed space. Blind diaphragms should not be made of thermoplastic foams.

6.5.8.7. A built-in parking lot for two or more cars must be separated from other premises of the house (block) by partitions and ceilings with a fire resistance rating of at least REI 45.

The door between the car park and living quarters must be equipped with a seal in the porches, a device for self-closing and must not open into the sleeping room.

6.6. Public buildings for administrative purposes and administrative buildings manufacturing enterprises

6.6.1. Degree of fire resistance, constructive fire hazard class, allowable height buildings and floor area within the fire compartment for public administrative buildings and administrative buildings of industrial and storage enterprises (detached buildings, outbuildings and inserts) (class F4.3) should be taken according to table 6.9.

Table 6.9

The degree of fire resistance of buildings	Constructive fire hazard class	Permissible height of buildings, m
			1	2	3	4, 5	6 - 9	10 - 16
I	C0	50	6000	5000	5000	5000	5000	2500
II	C0	50	6000	4000	4000	4000	4000	2200
II	C1	28	5000	3000	3000	2000	1200	-
III	C0	15	3000	2000	2000	1200	-	-
III	C1	12	2000	1400	1200	800	-	-
IV	C0	9	2000	1400	1200	-	-	-
IV	C1	6	2000	1400	-	-	-	-
IV	C2, C3	6	1200	800	-	-	-	-
V	C1 - C3	6	1200	800	-	-	-	-

6.6.2. In buildings of the IV degree of fire resistance, two floors or more high, elements load-bearing structures must have a fire resistance rating of at least R 45.

6.6.3. In buildings of I and II degrees of fire resistance, in order to ensure the required fire resistance limit of more than R 60 of the load-bearing elements of the building, it is allowed to use only structural fire protection (cladding, concrete, plaster, etc.).

The use of thin-layer fire-retardant coatings of steel load-bearing structures in buildings of I-II degrees of fire resistance is possible provided that they are used for structures with a reduced metal thickness according to GOST R 53295 of at least 5.8 mm. The use of thin-layer coatings for reinforced concrete structures is possible subject to the assessment of their fire resistance limit with applied fire protection agents.

6.6.4. In buildings of I, II, III degrees of fire resistance for attic floor it is allowed to accept the fire resistance limit of the bearing building structures R 45 with the provision of their fire hazard class K0 when separated from the lower floors by a type 2 fire ceiling. In this case, the attic floor should be divided by fire partitions of the 1st type into compartments with an area: for buildings of I and II degrees of fire resistance no more than 2000 sq. m, for buildings of the III degree of fire resistance - no more than 1400 sq. m. Fire partitions should rise above the roof: not less than 60 cm, if at least one of the elements of the attic or non-attic coating, with the exception of the roof, is made of materials of groups G3, G4; not less than 30 cm, if the elements of the attic or non-attic covering, with the exception of the roof, are made of materials of groups G1, G2.

Fire partitions may not rise above the roof if all elements of the attic or non-attic covering, with the exception of the roof, are made of materials of the NG group.

In the attics of buildings up to 10 floors inclusive, it is allowed to use wooden structures with structural fire protection that ensures their fire hazard class K0.

6.7. Public buildings for administrative purposes

6.7.1. The degree of fire resistance of canopies, terraces, galleries attached to the building, as well as other buildings and structures separated by fire walls can be taken one degree of fire resistance lower than the degree of fire resistance of the building.

6.7.2. When equipping premises with installations automatic fire extinguishing the areas indicated in Table 6.9 can be increased by 100%, with the exception of buildings of the IV degree of fire resistance of fire hazard classes C0 and C1, as well as buildings of the V degree of fire resistance.

If there are open openings in the ceilings of adjacent floors, the total area of ​​these floors should not exceed the floor area indicated in Table 6.9.

The floor area between the fire walls of one-story buildings with a two-story part occupying less than 15% of the built-up area of ​​the building should be taken as for a one-story building.

6.7.3. If there are automatic fire extinguishing installations on the attic floor, the area of ​​​​the compartments specified in clause 6.6.4 can be increased by no more than 1.2 times.

6.7.4. Enclosing structures of transitions between buildings must have fire resistance limits, equal to the limits fire resistance of the enclosing structures of the main building. Pedestrian and communication tunnels must have a fire hazard class K0. The walls of buildings in the places where passages and tunnels adjoin them should be provided for fire hazard class K0 with a fire resistance limit of REI 45. Doors in the openings of these walls leading to passages and tunnels must be type 2 fireproof.

6.7.5. In buildings above 4 floors as a translucent filling of doors, transoms (in doors, partitions and walls, including internal walls staircases) and partitions, tempered or reinforced glass and glass blocks should be used. In buildings with a height of 4 floors or less, the types of glass-transparent filling are not limited. In buildings over 4 stories high, stairwell doors leading to common corridors, the doors of elevator halls and tambours-locks must be deaf or with reinforced glass.

6.8. Public buildings

6.8.1. The floor area between fire walls of the 1st type, depending on the degree of fire resistance, the class of constructive fire hazard and the number of storeys of buildings, should not exceed that indicated in Table. 6.9, enterprise buildings consumer services(F3.5) - in the table. 6.10, trade enterprises (shops, F3.1) - in table. 6.11.

The degree of fire resistance of buildings	Constructive fire hazard class	Permissible height of buildings, m	Floor area within the fire compartment, sq. m, with the number of floors
			for one-story	for multi-storey buildings (no more than 6 floors)
I	C0	18	3000	2500
II	C0	18	3000	2500
II	C1	6	2500	1000
III	C0	6	2500	1000
III	C1	5	1000	-
IV	C0, C1	5	1000	-
IV	C2, C3	5	500	-
V	C1 - C3	5	500	-

2. In buildings of I and II degrees of fire resistance, in the presence of automatic fire extinguishing, the floor area between the fire walls can be increased by no more than twice.

3. When placing storerooms, office, household and technical premises on the upper floors of buildings of stores of I and II degrees of fire resistance, the height of buildings can be increased by one floor.

6.8.2. In buildings of I and II degrees of fire resistance, in the presence of automatic fire extinguishing, the floor area between the fire walls can be increased by no more than twice as compared to that established in Table. 6.9.

6.8.3. The floor area between the fire walls of one-story buildings with a two-story part occupying less than 15% of the built-up area of ​​the building should be taken as for one-story buildings in accordance with Table. 6.9.

6.8.4. In station buildings, instead of fire walls, it is allowed to install water deluge curtains in two strands located at a distance of 0.5 m and providing an irrigation intensity of at least 1 l / s per 1 m of curtain length with an operating time of at least 1 hour, as well as fire curtains, screens and other devices with a fire resistance rating of at least E 60.

6.8.5. In the buildings of air terminals of the 1st degree of fire resistance, the floor area between the fire walls can be increased to 10,000 square meters. m, if there are no warehouses, storerooms and other premises with the presence of combustible materials in the basement (basement) floors (except for luggage storage and personnel wardrobes). Storage chambers (except for those equipped with automatic cells) and dressing rooms should be separated from the rest of the basement with type 1 fire partitions and equipped with automatic fire extinguishing installations, and command and control centers with fire partitions.

6.8.6. In terminal buildings, the floor area between fire walls is not limited, provided that automatic fire extinguishing installations are equipped.

6.8.7. The degree of fire resistance of canopies, terraces, galleries attached to the building, as well as service and other buildings and structures separated by fire walls, can be taken one degree of fire resistance lower than the degree of fire resistance of the building.

6.8.8. In sports halls, halls of indoor skating rinks and halls of swimming pool baths (with and without seats for spectators), as well as in halls for preparatory classes pools and firing zones of indoor shooting ranges (including those located under stands or built into other public buildings) in excess of their area in relation to that established in Table. 6.9 fire walls should be provided between halls (in shooting ranges - a firing zone with a shooting gallery) and other rooms. In the premises of the vestibules and foyers, if their area is exceeded in relation to that established in Table. 6.9 instead of fire walls, translucent fire partitions of the 2nd type can be provided.

6.8.9. In buildings of I, II, III degrees of fire resistance, the execution of the attic floor is determined by the requirements of clause 6.6.4.

6.8.10. Enclosing structures of transitions between buildings (buildings) must have fire resistance limits corresponding to the main building (building). Pedestrian and communication tunnels should be designed from the materials of the NG group. The walls of buildings in the places where transitions and tunnels adjoin them should be provided from materials of the NG group with a fire resistance rating of R 120. Doors in the openings of these walls leading to transitions and tunnels must be type 2 fireproof.

6.8.11. For the storage of explosive materials, as well as X-ray films and other flammable materials (liquids), separate buildings should be provided for at least II degree of fire resistance.

Storerooms of flammable materials (goods) and combustible liquids in public buildings and structures should be located near the outer walls with window openings and separate them with type 1 fire partitions and type 3 ceilings, providing an entrance through a vestibule-gateway.

6.8.12. The degree of fire resistance of bath buildings and

-"- 350 IIC09 IC0, C1

6.8.19. Doors of pantries for storing combustible materials, workshops for processing combustible materials, switchboards, ventilation chambers and other fire hazardous technical rooms, as well as pantries for storing linen and ironing in children's rooms preschool institutions must have a fire resistance rating of at least EI 30.

C0I12

6.8.21. Buildings of specialized schools and boarding schools (for children with disabilities of physical and mental development) should be no higher than three floors.

6.8.22. In boarding schools, sleeping quarters should be located in blocks or parts of the building, separated from other rooms by fire walls or partitions.

6.8.23. Overlaps over basements buildings of schools and boarding schools of III and IV degrees of fire resistance must be fireproof of the 3rd type.

6.8.24. Degree of fire resistance, class of constructive fire hazard and the highest height of buildings educational institutions and institutions for advanced training (Form 4.2) should be taken depending on the number of seats in classrooms or halls according to Table. 6.14.

IIIC03 Up to 600 I, IIC0, C13 Not standardized openAnyAny3 Up to 600 I, IIC0, C13 Not standardized ClubsIVC2, C33 Up to 300 IVC15 -"- 300 IIIC05 -"- 400 IIC0, C18 <*> -"- 600 IC18 <*> Not standardized IC0Not standardized TheatersIC0Same <*>Auditoriums should be located no higher than the second floor.

6.8.39. Sliding partitions must be protected on both sides by materials of the NG group, providing a fire resistance rating of EI 45, with the exception of buildings of the V degree of fire resistance.

During the construction of any building, the organization of emergency exits, escape routes in emergency cases, and the location of funds are always considered at the design stage. But these points can be considered only if you know the degree of fire resistance of the building. Difficulties may arise with this at the present time, since most often the same type of structures are being built in cities. But then we will try to figure out how fire resistance is determined, on what it depends.

What is fire resistance?

This is the ability of structures and individual structures withstand the onslaught of fire without destruction and deformation. It is the degree of fire resistance of the building that will show how quickly the fire can spread throughout the structure if a fire occurs.

All indicators are determined taking into account SNiP. These standards allow you to determine the level of not only the building, but also all the materials that were used in the construction.

Flammability classification

1. Fireproof.
2. Difficult to be affected by fire. They can be made of combustible materials, but which have special treatment or cover. An example is wooden door lined with steel or covered with asbestos.
3. combustible. Have low temperature ignition and under the influence of fire quickly burn out.

Basis for determining fire resistance

As a determining basis for determining the degree of fire resistance of a building, the time that has elapsed from the moment the fire began to the appearance of the first noticeable defects is taken. These include:

• Cracks and damage to the integrity of the surface, which can facilitate the penetration of flames or products of its combustion.
• Increasing the temperature of materials by more than 160 degrees.
• Deformation of load-bearing structures and main units, which causes the collapse of the entire structure.

Have low degree fire resistance of buildings built of wooden structures, reinforced concrete are considered the safest in terms of fire, especially if the composition contains cement with high level fire resistance.

Dependence of fire resistance on materials

The ability of a building to resist fire largely depends on the materials from which it is built. They can be classified based on the following characteristics:

The degree of fire resistance of building structures depends on the time required for the deformation of the material:

• Ceramic bricks or silicate bricks begin to deform 300 minutes after the start of the fire.
• Concrete floors, more than 25 cm thick, after two hours.
• 75 minutes are required to start the deformation of plaster-coated wooden structures.
• An hour will pass before the door treated with fire retardant begins to deform.
• 20 minutes exposure to fire is enough.

Degree of fire resistance brick buildings quite high, which cannot be said about metal, which already at 1000 degrees turn into liquid state.

Assignment of a fire safety category

According to regulatory requirements, only after the structure is assigned a certain category according to fire safety, you can determine the degree of fire resistance of the building. And this is done on the basis of the following signs:

• By changing the indicators of thermal insulation, when compared with the state before the fire.
• By blocking effect, which eliminates the formation of cracks in structures.
• By reducing the ability to perform load-bearing functions.

When determining the degree of fire resistance of a building, the area of ​​\u200b\u200bthe structure and the quality of all materials used must be taken into account.

Characteristics of the degrees of fire resistance

Their determination is made on the basis of SNiP, the fire resistance of the main functional structures is always taken as the basis. Consider how many degrees of fire resistance of buildings and structures exist and what are their main characteristics:

Types of fire resistance

Special requirements for the ability to withstand fire are imposed on all building structures. For them, the following indicators are important:

• The ability to perform a load-bearing function.
• Thermal insulation.
• Integrity.

The safety of the building also plays an important role. Experts today divide the fire resistance of structures into two types:

1. Actual.
2. Required.

The actual degree of fire resistance of a building is the ability to withstand fire, which was determined during the examination. The available regulatory documents are taken as criteria for evaluation. For structures different type fire resistance limits have already been developed. This data is very easy to find and use for work.

The required fire resistance is the indicators that a building must have in order to comply with all fire safety standards. They are defined normative documents and depend on many characteristics of the structure:

• The total area of ​​the building.
• Number of floors.
• Purpose.
• Availability of means and installations for extinguishing fires.

If during the inspection it turned out that the actual degree of fire resistance of buildings and structures is equal to or exceeds the required one, then the structure complies with all standards.

Fire Hazard Classes

To determine the fire resistance of the entire building, structures are divided into several categories, and buildings into several classes.

1. KO is non-flammable. There are no materials in the premises that ignite quickly, and the main structures do not ignite spontaneously and ignite at temperatures close to 500 degrees.
2. K1 - low fire hazard. Minor damage may be allowed, but not more than 40 cm. No burning, no thermal effect.
3. K2 - moderate fire hazard. Damage can reach 80 cm, but there is no thermal effect.
4. K3 - fire hazard. Integrity violations of more than 80 cm, there is a thermal effect and fire is possible.

1. CO. All utility rooms, main structures and staircases with openings comply with the KO class.
2. C1. There may be slight damage to the leading structures up to K1, and the outer ones up to K2. Stairs and openings must be in excellent condition.
3. C2. Damage to the main structures can reach K2, external K3, and stairs up to K1.
4. C3. Stairs with openings are damaged up to K1, and everything else is not taken into account.

Rules for determining the resistance of a building to fire

It is not enough to know about the importance of fire resistance of buildings and structures, it is also important to be able to determine it. And there are some rules for this:

1. Testing a building involves having its plan at hand, and you will also need:

• Code of Practice for Ensuring Fire Resistance of Reinforced Concrete Structures.
• Guide to determining the limits of fire resistance.
• Manual for SNiP "Prevention of the spread of fire."

2. The fire resistance limit is determined by the time of exposure to the structure of fire. When the structures reach one of the limits, the fire is stopped.

3. Before starting testing, it is necessary to study the documentation for the building, where there is information about the materials and their approximate fire resistance.

4. It is necessary to pay attention in the documents to the existing conclusion on the use of special technologies to improve fire safety.

5. A preliminary study of the building also involves the consideration of all utility rooms, stairs and stairwells, attic compartments. They may be constructed from other materials or show visible damage at the time of testing.

6. Modern architecture often used in construction the latest technology, which may affect the strength and resistance to fire. These points must also be taken into account.

7. Before carrying out the determination of fire resistance, it is necessary to prepare extinguishing agents, check the serviceability of the hoses, and call the fire brigade.

When all the preliminary measures have been taken, then you can proceed directly to the practical determination of fire resistance.

Practical definition of resistance to fire

Coming to the practical part, it is important to take the architectural plan with you, even if it has been carefully studied. The next steps are:

An indicator of the fire resistance of the material will be the time of exposure to fire and the speed of its spread. For different buildings, this figure can vary from 20 minutes to 2.5 hours. The ignition rate is even less - from instantaneous to 40 cm per minute.

This is how the fire resistance of a building is calculated in practice.

Ways to improve fire resistance

It is not always possible to use only non-combustible or low-combustible materials during construction, so ways to increase their resistance to fire come to the rescue.

The most commonly used are:

If multi-component chemicals to improve fire resistance, it must be borne in mind that some of them contain organic matter, which decompose at temperatures above 300 degrees with the release of toxic substances. Therefore, it is better to give preference to mineral-based coatings with liquid glass.

It is not difficult to determine the fire resistance of buildings and structures. It's important to do everything preliminary preparations and we can assume that most of the work is done. The calculation can be attributed more to costly than complex. The most important thing is special care during testing and temperature control in the oven.

The approach to the construction of any buildings and structures should be based on safety from different points of view. And last but not least is fire safety. In emergency situations, human lives depend on the resistance of the structure to fire.

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Classification of buildings and structures by fire resistance.

In assessing the fire-prevention qualities of buildings and structures, their fire resistance is of great importance.

Fire resistance is the ability of building structural elements buildings to perform load-bearing and enclosing functions in a fire for a certain time. It is characterized by a fire resistance limit.

The fire resistance limits of the structures of the facility must be such that the structures retain their load-bearing and enclosing functions during the entire duration of the evacuation of people or their stay in places of collective protection. At the same time, fire resistance limits should be assigned without taking into account the effect of extinguishing agents on the development of a fire.

The fire resistance limit of building structures is determined by the time (h) from the start of a fire to the occurrence of one of the signs: a) the formation of through cracks in the structure; b) an increase in temperature on the unheated surface of the structure by an average of more than 140 ° C or at any point on this surface by more than 180 ° C compared to the temperature of the structure before the test, or more than 220 ° C regardless of the temperature of the structure before the test; d) loss of bearing capacity by the structure.

The fire resistance limit of individual building structures depends on their dimensions (thickness or section) and physical properties materials. For example, the stone walls of a building with a thickness of 120 mm. have a fire resistance limit of 2.5 hours, and with a thickness of 250 mm, the fire resistance increases to 5.5 hours.

The degree of fire resistance of a building depends on the degree of flammability and the fire resistance limit of its main building structures. All buildings and structures in terms of fire resistance are divided into five degrees (Table 32).

Table 32 Classification of buildings and structures by fire resistance.

Degree of fire resistance	Basic building structures
	bearing walls, stairwell walls, columns	outer walls of hinged panels and external half-timbered walls	slabs, floorings and other load-bearing structures of interfloor and attic floors	slabs, decks and other load-bearing structures of coatings	internal load-bearing walls (partitions)	fire walls
I	Fireproof (2.5)	Fireproof (0.5)	Fireproof (1.0)	Fireproof (0.5)	Fireproof (0.5)	Fireproof (2.5)
II	Fireproof (2.0)	Fireproof (0.25); slow-burning (0.5)	Fireproof (0.75)	Fireproof (0.25)	Fire resistant (0.25)	Fireproof (2.5)
III	Fireproof (2.0)	Fireproof (0.25); slow-burning (0.15)	Fire resistant (0.75)	combustible	Fire resistant (0.25)	Fireproof (2.5)
IV	Fire resistant (0.5)	Fire resistant (0.25)	Fire resistant (0.25)	»	Fire resistant (0.25)	Fireproof (2.5)
V	combustible	combustible	combustible	»	combustible	Fireproof (2.5)

Note. The limits of fire resistance (h) are indicated in brackets.

This division into degrees was introduced by SNiP II-A. 5-70, which gives nine notes on what to keep in mind when using the table.

Degree of fire resistance

fire resistance limit

Structural collapse;

Fire resistance limits:

– silicate brick – ~5 h

Table 3

Degree of fire resistance
I
II	Same. It is allowed to use unprotected steel structures in building coverings.
III
III a
III b
IV
IV a
V

- impregnation with flame retardants;

- facing;

- plaster.

- borax Na 2 B 4 O 7 * 10H 2 O.

asbestos cement sheets;

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		Need help from experts in determining the degree of fire resistance of the building! 3 storey building, wooden structures attic, metal roof. The walls are brick plastered. Interfloor floors are reinforced concrete, including the attic. Wooden structures treated with fire retardant. There is a controversial question what degree of fire resistance of the building 2 or 3. In accordance with the table. 21 FZ-123 and a manual for determining the degrees of fire resistance, it turns out that the building is of the second degree of fire resistance, but the attic is embarrassing. The inspector claims that 3 is only because of the wooden attic. I disagree (maybe I'm wrong). Reasonable answer required
		5.4.5. Fire resistance limits and fire hazard classes of attic structures in buildings of all degrees of fire resistance are not standardized, but roofing, rafters and lathing, as well as filing eaves overhangs it is allowed to be made of combustible materials, except in special cases. It is allowed to design gable structures with non-standardized fire resistance limits, while the gables must have a fire hazard class corresponding to the fire hazard class of the outer walls with outside. Information about the structures related to the elements of attic coverings is given by the design organization in the technical documentation for the building. In buildings of I - IV degrees of fire resistance with attic coverings, with rafters and (or) lathing made of combustible materials, the roof should be made of non-combustible materials, and rafters and the crate in buildings of the I degree of fire resistance should be treated with fire retardants of the I group of fire retardant efficiency, in buildings of the II - IV degrees of fire resistance with fire retardants not lower than the II group of fire retardant efficiency in accordance with GOST 53292, or to carry out their constructive fire protection that does not contribute to the latent spread of combustion. In buildings of classes C0, C1, the structures of cornices, filing of cornice overhangs of attic coverings should be made of materials NG, G1, or they should be sheathed with these elements sheet materials flammability group not less than G1. For these structures, the use of combustible heaters is not allowed (with the exception of a vapor barrier up to 2 mm thick), and they should not contribute to the latent spread of combustion.
		yahont ® why are you considering an attic to determine the fire resistance limit of a building? The attic is not a floor (see the term building and the term attic), and rooms can only be placed on a floor. You need to consider the building to the attic. And such constructions, as you described (brick walls, reinforced concrete floors, including the attic), as a rule, give the II degree.
		II CO
		II degree C0. The inspector is wrong. The theme of walls, marches and landings of stairs in the stairwell, by the way, is not disclosed. Maybe it is there that there is a reason for doubts about the III degree.
		Handsome Inspector! The degree of fire resistance of the building by eye determines! In fact, the degree of fire resistance is laid down in the project))
		Building codes and rules SNiP 2.01.02-85* "Fire safety standards" Appendix 2, in these standards, it is revealed how they are mainly distributed fire resistance, and how they can be identified. They are ancient, but very understandable. Stairs and marches are not indicated in them. According to your description, no doubt, II degree. The inspector is wrong.
		Thanks to everyone who responded!
		Discussion closed

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The conditions for the development of a fire in buildings and structures are largely determined by the degree of their fire resistance. Degree of fire resistance called the ability of a building (structure) as a whole to resist destruction in a fire. Buildings and structures according to the degree of fire resistance are divided into five degrees (I, II, III, IV, V). The degree of fire resistance of a building (structure) depends on the flammability and fire resistance of the main building structures and on the limits of the spread of fire through these structures.

By flammability, building structures are divided into fireproof, slow-burning and combustible. Fireproof are building structures made of fireproof materials. Flame-retardant structures are those made of slow-burning materials or combustible materials protected from fire and high temperatures by fireproof materials (for example, fire door, made of wood and covered with asbestos sheet and roofing steel).

The fire resistance of building structures is characterized by their fire resistance limit, which is understood as the time in hours, after which 1 of 3 signs occurs in case of fire:

1. Structure collapse;

2. Formation of through cracks or holes in the structure. (Combustion products penetrate into neighboring rooms);

3. Warming up the structure to temperatures that cause spontaneous ignition of substances in adjacent rooms (140-220 o).

Fire resistance limits:

- ceramic brick - 5 hours (25 cm-5.5; 38-11 hours)

– silicate brick – ~5 h

- concrete 25 cm thick - 4 hours (the cause of destruction is the presence of up to 8% water);

- a tree covered with plaster 2 cm thick (total 25 cm) 1 hour 15 minutes;

— metal constructions- 20 min (1100-1200 o C-metal becomes plastic);

— Entrance door, treated with fire retardant -1 h.

Porous concrete, hollow bricks have great fire resistance.

Unprotected metal structures have the lowest fire resistance limit, and reinforced concrete structures have the highest.

According to DBN 1.1.7-2002 “Fire protection. Fire safety of construction objects", all buildings and structures are divided into eight degrees according to fire resistance (see table.

Table 3

Fire resistance of buildings and structures

Degree of fire resistance	Design characteristic
I	Buildings with load-bearing and protective structures made of natural or artificial stone materials, concrete or reinforced concrete using sheet and slab non-combustible materials
II
III	Buildings with load-bearing and enclosing structures made of natural or artificial stone materials, concrete or reinforced concrete For ceilings, it is allowed to use wooden structures protected by plaster or hardly combustible sheet materials, as well as slab materials. Requirements regarding the fire resistance limit and the limits of fire spread are not established for the elements of the coating, while elements of attic coverings made of wood are amenable to fire retardant treatment
III a	Buildings predominantly with a frame structural scheme Frame elements - from steel unprotected structures Enclosing structures - from steel profiled sheets or other non-combustible sheet materials with slow-burning insulation
III b	Buildings are predominantly one-story with a frame structural scheme Frame elements - made of solid or glued wood, subjected to fire retardant treatment, which provides the desired boundary for the spread of fire Enclosing structures - made of panels or element-by-element assembly, made using wood or materials based on it Wood and other combustible materials protective structures must be subjected to fire retardant treatment or protected from the effects of fire and high temperatures in such a way as to ensure the desired border of the spread of fire
IV	Buildings with load-bearing and protective structures made of solid or glued wood and other combustible and slow-burning materials protected from the effects of fire and high temperatures by plaster and other sheet and slab materials attic floors from wood amenable to fire retardant treatment
IV a	Buildings are predominantly one-story with a frame structural scheme Frame elements - from steel unprotected structures Enclosing structures - from steel profiled sheets or other non-combustible materials with combustible insulation
V	Buildings, the load-bearing and protective structures of which are not subject to requirements regarding the limits of fire resistance and the limits of the spread of fire

Protection of wooden structures from fire:

To protect wooden structures from fire, apply:

- impregnation with flame retardants;

- facing;

- plaster.

Flame retardants - chemical substances, designed to impart fireproof properties to wood (French physicist Gay-Lussac. 1820 Ammonium salts).

Flame retardants - reduce release rates gaseous products, reduce the yield of resin as a result of chemical interaction with cellulose.

For the impregnation of wood used:

- ammonium phosphate (NH 4) 2 HPO 4

- ammonium sulfate (NH 4) 2 SO4

- borax Na 2 B 4 O 7 * 10H 2 O.

Deep impregnation is carried out in autoclaves at a pressure of 10-15 atm for 2-20 hours.

Soaking is carried out in a flame retardant solution at a temperature of 90 ° C for 24 hours.

Impregnation with flame retardants transforms wood into the category of hardly combustible materials. Surface treatment - prevents fire wood within a few minutes.

Facing and plaster - protect wooden structures from fire (slow heating).

Wet plaster - fire protection 15-20 min.

Facing materials: gypsum plaster(fire protection 10 min);

asbestos cement sheets;

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Fire resistance of buildings and structures

The conditions for the development of a fire in buildings and structures are largely determined by the degree of their fire resistance.

Degree of fire resistance called the ability of a building (structure) as a whole to resist destruction in a fire. Buildings and structures according to the degree of fire resistance are divided into five degrees (I, II, III, IV, V). The degree of fire resistance of a building (structure) depends on the flammability and fire resistance of the main building structures and on the limits of the spread of fire through these structures.

By flammability, building structures are divided into fireproof, slow-burning and combustible. Fireproof are building structures made of fireproof materials. Fire-retardant structures are those made of fire-retardant materials or combustible materials protected from fire and high temperatures by fireproof materials (for example, a fire door made of wood and covered with asbestos sheet and roofing steel).

The fire resistance of building structures is characterized by their fire resistance limit, which is understood as the time in hours, after which 1 of 3 signs occurs in case of fire:

1. Structure collapse;

2. Formation of through cracks or holes in the structure. (Combustion products penetrate into neighboring rooms);

3. Warming up the structure to temperatures that cause spontaneous ignition of substances in adjacent rooms (140-220 o).

Fire resistance limits:

- ceramic brick - 5 hours (25 cm-5.5; 38-11 hours)

– silicate brick – ~5 h

- concrete 25 cm thick - 4 hours (the cause of destruction is the presence of up to 8% water);

- a tree covered with plaster 2 cm thick (total 25 cm) 1 hour 15 minutes;

- metal structures - 20 min (1100-1200 o C-metal becomes plastic);

- front door treated with flame retardant -1 hour.

Porous concrete, hollow bricks have great fire resistance.

Unprotected metal structures have the lowest fire resistance limit, and reinforced concrete structures have the highest.

According to DBN 1.1.7-2002 “Fire protection. Fire safety of construction objects”, all buildings and structures are divided into eight degrees according to fire resistance (see Table 3).

Table 3

Fire resistance of buildings and structures

Degree of fire resistance	Design characteristic
I	Buildings with load-bearing and protective structures made of natural or artificial stone materials, concrete or reinforced concrete using sheet and slab non-combustible materials
II	Same. It is allowed to use unprotected steel structures in building coverings.
III	Buildings with load-bearing and enclosing structures made of natural or artificial stone materials, concrete or reinforced concrete For ceilings, it is allowed to use wooden structures protected by plaster or hardly combustible sheet materials, as well as slab materials. Requirements regarding the fire resistance limit and the limits of fire spread are not established for the elements of the coating, while elements of attic coverings made of wood are amenable to fire retardant treatment
III a	Buildings predominantly with a frame structural scheme Frame elements - from steel unprotected structures Enclosing structures - from steel profiled sheets or other non-combustible sheet materials with slow-burning insulation
III b	Buildings are predominantly one-story with a frame structural scheme Frame elements - made of solid or glued wood, subjected to fire retardant treatment, which provides the desired boundary for the spread of fire Enclosing structures - made of panels or element-by-element assembly, made using wood or materials based on it Wood and other combustible materials protective structures must be subjected to fire retardant treatment or protected from the effects of fire and high temperatures in such a way as to ensure the desired border of the spread of fire
IV	Buildings with load-bearing and protective structures made of solid or glued wood and other combustible and slow-burning materials protected from the effects of fire and high temperatures by plaster and other sheet and slab materials timber floors are fire-retardant
IV a	Buildings are predominantly one-story with a frame structural scheme Frame elements - from steel unprotected structures Enclosing structures - from steel profiled sheets or other non-combustible materials with combustible insulation
V	Buildings, the load-bearing and protective structures of which are not subject to requirements regarding the limits of fire resistance and the limits of the spread of fire

Protection of wooden structures from fire:

To protect wooden structures from fire, apply:

- impregnation with flame retardants;

- facing;

- plaster.

Flame retardants are chemicals designed to impart fireproof properties to wood (French physicist Gay-Lussac. 1820 Ammonium salts).

Flame retardants - reduce the rate of release of gaseous products, reduce the yield of resin as a result of chemical interaction with cellulose.

For the impregnation of wood used:

- ammonium phosphate (NH 4) 2 HPO 4

- ammonium sulfate (NH 4) 2 SO4

- borax Na 2 B 4 O 7 * 10H 2 O.

Deep impregnation is carried out in autoclaves at a pressure of 10-15 atm for 2-20 hours.

Soaking is carried out in a flame retardant solution at a temperature of 90 ° C for 24 hours.

Impregnation with flame retardants transforms wood into the category of hardly combustible materials. Surface treatment - prevents fire wood within a few minutes.

Facing and plaster - protect wooden structures from fire (slow heating).

Wet plaster - fire protection 15-20 min.

Facing materials: gypsum plaster (fire protection 10 min);

asbestos cement sheets;

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How to determine the indicators of the actual fire resistance limit and fire hazard class of a building structure?

Question:

Is it possible to use wooden structures as load-bearing roof structures in a school building? The building has II degree of fire resistance, functional fire hazard class F1.1.

Answer:

In accordance with Article 36 federal law dated July 22, 2008 N 123-FZ "Technical regulations on fire safety requirements" (as amended on June 23, 2014), building structures for fire hazard are divided into the following classes:

1) non-flammable (K0);

2) low fire hazardous (K1);

3) moderately flammable (K2);

4) fire hazardous (K3).

Currently, when determining the actual fire hazard classes of building structures, the following is used:

— GOST 30403-2012 “Building structures.

Test Method for Fire Hazard".

Currently, when determining the actual limits of fire resistance of structures, the following are used:

— GOST 30247.0-94 “Building structures. Test methods for fire resistance. General requirements»;

— GOST 30247.1-94 “Building structures. Test methods for fire resistance. Bearing and enclosing structures.

Based on the results of fire tests, test reports are drawn up (clause 12 of GOST 30247.0-94, clause 10 of GOST 30247.1-94, clause 11 of GOST 30403-2012), which indicate the relevant data, including the actual fire resistance limits of building structures and actual fire hazard classes of building structures.

Accordingly, in order to determine the actual fire resistance limits and fire hazard classes of building structures, it is necessary to conduct fire tests in an accredited testing laboratory.

Based on information only about the material from which the building structure is made, it is impossible to determine the indicators of the actual fire resistance limit and fire hazard class of the building structure.

In accordance with part 10 of article 87 of the Federal Law of July 22, 2008 N 123-FZ, the fire resistance limits and fire hazard classes of building structures similar in shape, materials, design to building structures that have passed fire tests can be determined by the calculation and analytical method established by regulatory documents on fire safety.

At the moment, information about the actual fire resistance limits and fire hazard classes of various building structures that have previously passed fire tests is given in the Collections " Technical information(to help the inspector of the State Fire Service)”, published annually by the Federal State Budgetary Institution “All-Russian Research Institute of Fire Defense” of the Ministry of Emergency Situations of Russia.

building structures with actual class fire hazard K1 (low fire hazard), K2 (moderate fire hazard), K3 (fire hazardous) can only be used if the required structural fire hazard class of the building is allowed C1, C2, C3, respectively (Table 22 of the Federal Law of July 22, 2008 N 123- FZ).

The required degree of fire resistance and the required class of constructive fire hazard of buildings is determined in accordance with SP 2.13130.2012 “Fire protection systems. Ensuring the fire resistance of protected objects ”(as amended on October 23, 2013) based on certain parameters building being designed (for example, functional purpose buildings, height of buildings or structures, number of storeys, floor area within the fire compartment, building category for explosion and fire hazard, number of seats, etc.).

Further, in accordance with Table N 21 of the Federal Law of July 22, 2008 N 123-FZ, based on the required degree of fire resistance of the building, the minimum required fire resistance limits of building structures are determined.

In accordance with table N 22 FZ N 123-FZ, based on the required class of constructive fire hazard of the building, the minimum required classes fire hazard of building structures.

At the same time, it should be taken into account that fire safety requirements will be met only if the building structure meets both the required fire resistance limit and the required fire hazard class at the same time.

Accordingly, it is initially necessary, on the basis of SP 2.13130.2012, based on certain parameters of the designed building (for example, the functional purpose of the building, the height of buildings or structures, number of storeys, floor area within the fire compartment, number of seats, etc.) to determine the required degree of fire resistance and the required class of constructive fire hazard of buildings.

Further, in accordance with Table N 21 of the Federal Law of July 22, 2008 N 123-FZ, based on the required degree of fire resistance of the building, the minimum required fire resistance limits of specific building structures are determined.

In accordance with Table N 22 FZ N 123-FZ, based on the required structural fire hazard class of the building, the minimum required fire hazard classes of specific building structures are determined.

Further, based on certain minimum required fire hazard classes and minimum required fire resistance limits of specific building structures based on fire test reports or information on actual fire resistance limits and fire hazard classes given in the Collections "Technical Information (to assist the inspector of the State Fire Service)", select building structure.

Based on information only about the material from which the building structure is made, it is impossible to determine the indicators of the actual fire resistance limits and fire hazard classes of building structures.

In accordance with paragraph 5.4.5 of SP 2.13130.2012, the fire resistance limits and fire hazard classes of attic structures in buildings of all degrees of fire resistance are not standardized, and the roof, rafters and lathing, as well as filing of eaves overhangs, are allowed to be made of combustible materials, with the exception of specially stipulated cases.

It is allowed to design gable structures with non-standardized fire resistance limits, while the gables must have a fire hazard class corresponding to the fire hazard class of the outer walls from the outside.

Information about the structures related to the elements of attic coverings is given by the design organization in the technical documentation for the building.

In buildings of I-IV degrees of fire resistance with attic coverings, with rafters and (or) lathing made of combustible materials, the roof should be made of non-combustible materials, and the rafters and lathing in buildings of I degree of fire resistance should be treated with fire retardants of group I of fire retardant efficiency, in buildings of II-IV degrees of fire resistance with fire retardants not lower than group II of fire retardant efficiency in accordance with GOST 53292 *, or perform their constructive fire protection that does not contribute to the latent spread of combustion.

In buildings of classes C0, C1, the structures of cornices, filing of cornice overhangs of attic coverings should be made of materials NG, G1, or these elements should be sheathed with sheet materials of a flammability group of at least G1. For these structures, the use of combustible heaters is not allowed (with the exception of a vapor barrier up to 2 mm thick) and they should not contribute to the latent spread of combustion.