EN 1991-1-3:2025

SLOVENSKI STANDARD
oSIST prEN 1991-1-3:2023
01-maj-2023
Evrokod 1 - Vplivi na konstrukcije - 1-3. del: Obtežba snega
Eurocode 1 - Actions on structures - Part 1-3: Snow loads
Eurocode 1 - Einwirkungen auf Tragwerke - Teil 1-3: Allgemeine Einwirkungen -
Schneelasten
Eurocode 1 - Actions sur les structures - Partie 1-3 : Charges de neige
Ta slovenski standard je istoveten z: prEN 1991-1-3
ICS:
91.010.30 Tehnični vidiki Technical aspects
oSIST prEN 1991-1-3:2023 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

oSIST prEN 1991-1-3:2023
oSIST prEN 1991-1-3:2023
DRAFT
EUROPEAN STANDARD
prEN 1991-1-3
NORME EUROPÉENNE
EUROPÄISCHE NORM
March 2023
ICS 91.010.30 Will supersede EN 1991-1-3:2003
English Version
Eurocode 1 - Actions on structures - Part 1-3: General
actions - Snow loads
Eurocode 1 - Actions sur les structures - Partie 1-3: Eurocode 1 - Einwirkungen auf Tragwerke - Teil 1-3:
Actions générales - Charges de neige Allgemeine Einwirkungen, Schneelasten
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 250.
If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations
which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC
Management Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2023 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 1991-1-3:2023 E
worldwide for CEN national Members.

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prEN 1991-1-3:2023 (E)
Contents Page
European foreword . 4
Introduction . 5
1 Scope . 8
1.1 Scope of EN 1991-1-3 . 8
1.2 Assumptions . 8
2 Normative references . 8
3 Terms, definitions and symbols . 8
3.1 Terms and definitions . 8
3.2 Symbols and abbreviations . 10
3.2.1 Latin upper-case letters . 10
3.2.2 Latin lower case letters . 10
3.2.3 Greek lower-case letters . 11
4 Design situations . 12
4.1 General. 12
4.2 Normal conditions . 12
4.3 Exceptional conditions . 12
5 Modelling of snow load . 12
5.1 Classification of actions . 12
5.2 Design assisted by testing . 12
6 Snow load on the ground . 13
6.1 Characteristic values . 13
6.2 Treatment of exceptional snow loads on the ground . 13
7 Snow load on roofs . 13
7.1 Load arrangements . 13
7.2 Determination of snow load. 14
7.3 Exposure coefficient . 14
7.4 Thermal coefficient . 15
7.5 Snow load shape coefficients . 16
7.5.1 Field of application . 16
7.5.2 Flat roofs . 16
7.5.3 Pitched roofs . 19
7.5.4 Multi-span roofs . 21
7.5.5 Cylindrical roofs . 22
7.5.6 Domes . 24
7.5.7 Roof abutting and close to taller construction works . 25
8 Local Effects . 28
8.1 Local verifications . 28
8.2 Drifting at obstructions . 28
8.3 Drifting at parapets . 29
8.4 Snow overhanging the edge of a roof . 30
8.5 Snow loads on snow guards and other obstacles . 31
8.6 Drifting at intersecting pitched roofs . 31
Annex A (informative) Ground snow load maps . 33
A.1 Use of this Informative Annex . 33
A.2 Scope and field of application . 33
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A.3 Treatment of ground snow load measurements . 33
A.4 Zoning . 34
A.5 Climate change effect . 34
Annex B (informative) Adjustment of ground snow load to return period . 35
B.1 Use of this Informative Annex . 35
B.2 Scope and field of application . 35
B.3 Adjustment of the ground snow load according to the return period . 35
Annex C (informative) Bulk snow weight density . 37
C.1 Use of this Informative Annex . 37
C.2 Scope and field of application . 37
C.3 Bulk snow weight density . 37
Bibliography . 38

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European foreword
This document (prEN 1991-1-3:2023) has been prepared by Technical Committee CEN/TC 250
“Structural Eurocodes”, the secretariat of which is held by BSI.
CEN/TC 250 is responsible for all Structural Eurocodes and has been assigned responsibility for
structural and geotechnical design matters by CEN.
This document is currently submitted to the CEN Enquiry.
This document will supersede EN 1991-1-3:2003.
The first generation of EN Eurocodes was published between 2002 and 2007. This document forms part
of the second generation of the Eurocodes, which have been prepared under Mandate M/515 issued to
CEN by the European Commission and the European Free Trade Association.
The Eurocodes have been drafted to be used in conjunction with relevant execution, material, product
and test standards, and to identify requirements for execution, materials, products and testing that are
relied upon by the Eurocodes.
The Eurocodes recognize the responsibility of each Member State and have safeguarded their right to
determine values related to regulatory safety matters at national level through the use of National
Annexes.
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Introduction
0.1 Introduction to the Eurocodes
The structural Eurocodes comprise the following standards generally consisting of a number of Parts:
— EN 1990, Eurocode: Basis of structural and geotechnical design
— EN 1991, Eurocode 1: Actions on structures
— EN 1992, Eurocode 2: Design of concrete structures
— EN 1993, Eurocode 3: Design of steel structures
— EN 1994, Eurocode 4: Design of composite steel and concrete structure
— EN 1995, Eurocode 5: Design of timber structures
— EN 1996, Eurocode 6: Design of masonry structures
— EN 1997, Eurocode 7: Geotechnical design
— EN 1998, Eurocode 8: Design of structures for earthquake resistance
— EN 1999, Eurocode 9: Design of aluminium structures
— New parts are under development, e.g. Eurocode for design of structural glass
The Eurocodes are intended for use by designers, clients, manufacturers, constructors, relevant
authorities (in exercising their duties in accordance with national or international regulations),
educators, software developers, and committees drafting standards for related product, testing and
execution standards.
NOTE Some aspects of design are most appropriately specified by relevant authorities or, where not specified,
can be agreed on a project-specific basis between relevant parties such as designers and clients. The Eurocodes
identify such aspects making explicit reference to relevant authorities and relevant parties.
0.2 Introduction to EN 1991
(1) EN 1991 provides the actions to be considered for the structural design of buildings, bridges and
other civil engineering works, or parts thereof, including temporary structures, in conjunction with
EN 1990 and the other Eurocodes.
(2) The actions on structures, including in some cases geotechnical structures in conjunction with
EN 1997 as appropriate, provided in EN 1991 are intended to be applied in conjunction with the other
Eurocodes for the verification of safety, serviceability and durability, as well as robustness of structures,
including the execution phase.
(3) The application of this document for the verifications mentioned in (2) follows the limit state principle
and is based on the partial factor method, unless explicitly prescribed differently.
(4) EN 1991 does not cover the specific requirements of actions for seismic design, unless explicitly
stated in EN 1998. Provisions related to such requirements are given in EN 1998, which complements
and is consistent with EN 1991.
(5) EN 1991 is also applicable in the case of existing structures for their:
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— structural assessment,
— design of repairs, improvements and alterations,
— assessment for changes of use.
NOTE In this case additional or amended provisions can be necessary.
(6) EN 1991 is also applicable to the design of structures where materials or actions outside the scope of
the other Eurocodes are involved.
NOTE In this case additional or amended provisions can be necessary.
0.3 Introduction to EN 1991-1-3
EN 1991-1-3 gives design guidance and actions from snow for the structural design of buildings and civil
engineering works.
EN 1991-1-3 is addressed to all parties involved in construction activities (e.g. public authorities, clients,
designers, contractors, producers, consultants, etc.).
0.4 Verbal forms used in the Eurocodes
The verb “shall” expresses a requirement strictly to be followed and from which no deviation is permitted
in order to comply with the Eurocodes.
The verb “should” expresses a highly recommended choice or course of action. Subject to national
regulation and/or any relevant contractual provisions, alternative approaches could be used/adopted
where technically justified.
The verb “may” expresses a course of action permissible within the limits of the Eurocodes.
The verb “can” expresses possibility and capability; it is used for statements of fact and clarification of
concepts.
0.5 National Annex for EN 1991-1-3
National choice is allowed in this standard where explicitly stated within notes. National choice includes
the selection of values for Nationally Determined Parameters (NDPs).
The national standard implementing EN 1991-1-3 can have a National Annex containing all national
choices to be used for the design of buildings and civil engineering works to be constructed in the relevant
country.
When no national choice is given, the default choice given in this standard is to be used.
When no national choice is made and no default is given in this standard, the choice can be specified by a
relevant authority or, where not specified, agreed for a specific project by appropriate parties.
National choice is allowed in EN 1991-1-3 through notes to the following clauses:
4.3 (1) NOTE 7.4 (2) NOTE 2 8.1 (1) NOTE 1
6.1 (1) NOTE 1 7.4 (4) NOTE 1 8.2 (2) NOTE
6.1 (1) NOTE 2 7.4 (5) NOTE 1 8.3 (1) NOTE
6.2 (1) NOTE 7.5.2 (3) NOTE 8.4 (1) NOTE
7.3 (2) Table 7.1 7.5.3 (3) Table 7.3 8.4 (3) NOTE 1
7.3 (2) NOTE 2 7.5.3 (4) NOTE 8.4 (3) NOTE 2
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7.4 (1) NOTE 7.5.4 (2) NOTE 1 8.6 (1) NOTE 1
7.4 (2) NOTE 1 7.5.4 (2) NOTE 2 8.6 (1) NOTE 2
National choice is allowed in EN 1991-1-3 on the application of the following informative annexes:
Annex A Annex B Annex C
The National Annex can contain, directly or by reference, non-contradictory complementary information
for ease of implementation, provided it does not alter any provisions of the Eurocodes.
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1 Scope
1.1 Scope of EN 1991-1-3
(1) EN 1991-1-3 gives principles and rules to determine the values of loads due to snow to be used for
the structural design of buildings and civil engineering works.
(2) This Part does not apply to sites at altitudes above 1500 m, unless otherwise specified.
NOTE For rules for the treatment of snow loads for altitudes above 1500 m see 6.1.
(3) This Part does not give guidance on specialist aspects of snow loading, for example:
— impact snow loads resulting from snow sliding off or falling from a higher roof;
— changes in shape or size of the construction works due to the presence of snow or the accretion of
ice which could affect the wind action;
— loads in areas where snow is present all year round;
— lateral loading due to snow creep (e.g. lateral loads exerted by drifts);
— loads due to artificial snow.
1.2 Assumptions
The assumptions given in FprEN 1990:2022, 1.2 apply to EN 1991-1-3.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
NOTE See the Bibliography for a list of other documents cited that are not normative references, including
those referenced as recommendations (i.e. in “should” clauses), permissions (“may” clauses), possibilities (“can”
clauses), and in notes.
FprEN 1990:2022, Eurocode — Basis of structural and geotechnical design
3 Terms, definitions and symbols
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in FprEN 1990 and the following
apply.
3.1.1
characteristic value of snow load on the ground
s
k
snow load on the ground at the relevant site, based on an annual probability of exceedance of 0,02,
excluding exceptional snow loads
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3.1.2
altitude of the site
A
height above mean sea level of the site where the structure is to be located, or is already located for an
existing structure
3.1.3
exceptional snow load on the ground
s
Ad
load of the snow layer on the ground resulting from a snow fall which has an exceptionally infrequent
likelihood of occurring
Note 1 to entry See note to 4.3 (1) for locations where this can occur
3.1.4
characteristic value of snow load on the roof
s
product of the characteristic snow load on the ground and the coefficients defined in 3.1.7 to 3.1.9
Note 1 to entry: In accordance with FprEN 1990:2022, 6.1.2.3 (2), the characteristic value of snow load on the roof
corresponds to an upper value with an annual probability of exceedance of 0,02 or to a nominal value.
3.1.5
balanced snow load arrangement on the roof
load arrangement which describes the uniformly distributed snow load on the roof, affected by the shape
of the roof and its exposure to wind
3.1.6
unbalanced snow load arrangement on the roof
load arrangement which describes the snow load distribution resulting from snow having been moved
from one location to another location on a roof or off the roof, depending on the exposure of the roof to
wind and the effects of sliding
Note 1 to entry: Unbalanced load arrangements given in this standard assume that wind can have any direction.
3.1.7
snow load shape coefficient
μ
i
ratio of the characteristic ground snow load on the roof to the snow load on the ground, including the
effect of wind exposure but without the influence of thermal effects
3.1.8
thermal coefficient
C
t
coefficient defining the change of snow load on roofs as a function of the heat flux through the roof
3.1.9
exposure coefficient
C
e
coefficient defining the reduction or increase of snow load on a roof of an unheated building due to the
roof exposure to wind, as a fraction of the characteristic snow load on the ground
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3.1.10
flat roof
roof with pitch angles between 0 and 5 degrees, 0° ≤ α ≤ 5°
3.2 Symbols and abbreviations
For the purposes of this European Standard, the following symbols, specific to this Part, apply, together
with the general notations given in FprEN 1990:2022, Clause 3.
NOTE The notation used is based on ISO 3898:2013.
3.2.1 Latin upper-case letters
C exposure coefficient
e
C thermal coefficient
t
C coefficient for exceptional snow loads
esl
C exposure coefficient for flat roof
e,F
A altitude of the site
F force per unit length exerted by a sliding mass of snow
s
L length of the longer side of the flat roof
L effective roof length
c
W length of the shorter side of the flat roof
3.2.2 Latin lower case letters
b width of construction work or lateral distance of tilted panels on flat roofs
d depth of the snow layer
h reference height for the calculation of the snow load shape coefficient
h height of the parapet
p
k coefficient to take account of the irregular shape of snow
l length of snow drift or snow loaded area
s
s characteristic snow load on the roof
s characteristic value of snow on the ground at the relevant site
k
s design value of exceptional snow load on the ground at the relevant site
Ad
s snow load per unit length due to the overhang
e
s rain-on-snow surcharge
R
w width of the obstruction/parapet
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3.2.3 Greek lower-case letters
α angle of pitch of roof
α intersection angle
inter
β angle between the horizontal and the tangent to the curve for a cylindrical roof
γ snow weight density
δ snow drift factor
μ snow load shape coefficient for flat roofs
μ snow load shape coefficient for mono-pitched and pitched roofs
μ basic snow load shape coefficient for pitched roofs
2,b
μ lower limit for the snow load shape coefficient for the roof pitch with a retention device at
2,p
the lower edge
μ snow load shape coefficient taking into account the wind driven part of the snow on
2,w
pitched roofs
μ snow load shape coefficient for multi-span roofs
maximum value of the snow load shape coefficient for multi-span roofs
μ3max
μ snow load shape coefficient for cylindrical roofs and domes
μ snow load shape coefficient for roof abutting to taller construction works
μ snow load shape coefficient for local drifting at obstructions
μ snow load shape coefficient for local drifting at parapets
μ snow load shape coefficient for local drifting at intersecting pitched roofs
μ maximum value of the snow load shape coefficient for local drifting at intersecting pitched
8max
roofs
μ upper limit for the snow load shape coefficient for flat roofs with tilted panels
p
pertinent snow load shape coefficient for the lower roof (roof abutting to taller
µ
L
construction works)
pertinent snow load shape coefficient for the upper roof (roof abutting to taller
µ
U
construction works)
snow load shape coefficient taking into account the sliding part from the upper roof (roof
µ
s
abutting to taller construction works)
snow load shape coefficient taking into account the wind driven part of the drift,

µ
w
originating from erosion of the snow cover on both the upper and lower roofs (roof
abutting to taller construction works)
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4 Design situations
4.1 General
(1) The snow loads shall be determined for each relevant design situation identified in accordance with
FprEN 1990:2022, 5.2.
(2) Further to the fundamental (persistent and transient) design situation (see 4.2 and 4.3), accidental
design situation should be considered where exceptional conditions apply (see 4.3).
4.2 Normal conditions
(1) For locations where exceptional snow falls (see 5.1 (3)) are unlikely to occur, the fundamental
(persistent and transient) design situation should be used for both the balanced and the unbalanced snow
load arrangements determined as specified in 7.1.
(2) For local effects (see Clause 8), the fundamental (persistent and transient) design situation should be
used.
4.3 Exceptional conditions
(1) For locations where exceptional snow loads on the ground (see 5.1 (3)) are likely to occur the
following apply:
a) the fundamental (persistent and transient) design situation should be used for both the balanced and
the unbalanced snow load arrangements determined as specified in 7.1, and
b) the accidental design situation should be used for both the balanced and the unbalanced snow load
arrangements determined as specified in 6.2 and 7.1.
NOTE Exceptional conditions (which can include geographical locations) can be defined in the National Annex
for use in a country.
(2) For local effects a relevant design situation should be used.
NOTE For specification of design situations applicable to local effects see Clause 8.
5 Modelling of snow load
5.1 Classification of actions
(1) Snow loads shall be classified as variable, fixed actions, unless otherwise specified in this standard.
NOTE See FprEN 1990:2022, 6.1.1 (4).
(2) Snow loads covered in this standard should be classified as static actions.
NOTE See FprEN 1990:2022, 6.1.1 (4).
(3) In exceptional conditions (see 4.3), exceptional snow loads on the ground may be treated as accidental
actions instead of variable actions depending on geographical locations.
5.2 Design assisted by testing
(1) For roof shapes not covered or for project specific circumstances, scale model studies in wind tunnels
or water flumes and/or methods of computational fluid dynamics may be used to determine snow loads
on construction works.
NOTE See also FprEN 1990:2022, 7.3 (3) for achievement of the level of reliability required.
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(2) The specific circumstances should be as specified by the relevant authority or agreed for a specific
project by the relevant parties.
(3) All prediction models should be calibrated against field data, taking into account simplifications and
assumptions about snow accumulation processes.
NOTE See also FprEN 1990:2022, Annex D and ISO 4355:2013, Annex G.
6 Snow load on the ground
6.1 Characteristic values
(1) The characteristic value of snow load on the ground (s ) should be determined in accordance with
k
FprEN 1990:2022, 6.1.2.3 (2) and the definition for characteristic snow load on the ground given in 3.1.1.
NOTE 1 Characteristic values of ground snow load at sites for altitudes up to 1500 m can be set by the National
Annex for use in a country.
NOTE 2 Rules for the treatment of snow loads for altitudes above 1500 m can be set by the National Annex.
NOTE 3 For ground snow load values associated to different return periods, see Annex B.
(2) As an alternative to (1), the characteristic value of snow load on the ground (s ) may be defined by
k
means of an appropriate statistical analysis of available measurements, when specified by the relevant
authority or, where not specified, agreed for a specific project by the relevant parties.
NOTE Further guidance on determination of characteristic ground snow loads can be found in Annex A.
6.2 Treatment of exceptional snow loads on the ground
(1) For locations where exceptional snow loads on the ground are likely to occur (see 4.3), they
should be determined by:
s = Cs  (6.1)
Ad esl k
where
s is the design value of exceptional snow load on the ground for the given location;
Ad
C is the coefficient for exceptional snow loads;
esl
s is the characteristic value of snow load on the ground for a given location (see 3.1.1).
k
NOTE The value of C is 2,0 unless the National Annex gives a different value for use in a country.
esl
7 Snow load on roofs
7.1 Load arrangements
(1) The following load arrangements should be taken into account separately:
— balanced snow load on roofs (see 3.1.5);
— unbalanced snow load on roofs (see 3.1.6).
NOTE Properties of a roof or other factors causing different deposition patterns can include:
—  the shape of the roof;
—  its thermal properties;
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—  the roughness of its surface;
—  the amount of heat generated under the roof;
—  the proximity of nearby buildings;
—  the surrounding terrain;
—  the local meteorological climate, in particular its windiness, temperature variations, exposure to solar radiation,
and likelihood of precipitation (either as rain or as snow).
(2) Snow loads on roofs should be assumed to act vertically and refer to a horizontal projection of the
roof area.
(3) When artificial removal or redistribution of snow on a roof is anticipated, the structure of the roof
should be designed for suitable load arrangements, including non-symmetrical loading.
NOTE The load arrangements according to this Section have been derived for natural deposition patterns only.
Load arrangements due to the artificial removal can lead to more unfavourable load effects in comparison to the
balanced and unbalanced load arrangements provided in Clause 7.
7.2 Determination of snow load
(1) Snow loads on roofs shall be determined:
a) for the fundamental (persistent and transient) design situations by using Formula (7.1) (normal
conditions, see 4.2):
s = µ C s (7.1)
it k
b) for the accidental design situations by using Formula (7.2) (exceptional conditions, see 4.3):
s = µ C s (7.2)
i t Ad
where, further to the symbols defined in 6:
μ is the snow load shape coefficient (see 7.5), function of the wind exposure of the site
i
(through the exposure coefficient C – see 7.3) and of the geometry of the roof;
e
C is the thermal coefficient (see 7.4).
t
NOTE Where the snow load shape coefficients in 7.5 depend on sk, the values of snow load shape coefficients
for exceptional snow loads can be estimated by replacing sk by sAd.
(2) Special consideration should be taken in cases where snow can be redistributed from the ground to
the roof.
NOTE This can be the case in wind exposed areas for low-rise buildings.
7.3 Exposure coefficient
(1) The exposure coefficient C should be determined taking into account the snow redistribution by
e
wind.
NOTE In general snow redistribution depends on several effects, such as snow physical properties, amount of
available snow and wind exposure conditions.
(2) The exposure coefficient C may be determined considering the wind exposure conditions of the roof.
e
NOTE 1 The wind exposure conditions, and the corresponding values of Ce are given in Table 7.1 unless the
National A
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