Preface

This is the first edition of CAN/CSA-S502, Managing changing snow load risks for buildings in Canada's North.

The objective of this Standard is to inform communities on measures for safe roof snow removal from existing buildings and for protection of building occupants and assets from overloading risks due to increasing accumulations and weights. Procedures that can reduce risks for roof and building collapses are outlined, including procedures for monitoring heavy snow and ice accumulations, safe removal of snow on roofs when needed, and for maintenance and snow removal planning.

CSA Group received funding for the development of this Standard from Standards Council of Canada, as part of the Northern Infrastructure Standardization Initiative, supported by the Government of Canada's Clean Air Agenda.

This Standard was prepared by the Working Group on Changing Snow Loads in the North, under the jurisdiction of the Technical Committee on Northern Built Infrastructure and the Strategic Steering Committee on Construction and Civil Infrastructure, and has been formally approved by the Technical Committee. This Standard has been approved as a National Standard of Canada by the Standards Council of Canada.

Introduction

0.1 General

As climate conditions continue changing, Northern communities need to be prepared to deal with the impacts arising from increases in snow weights (loads) on existing buildings.

Snow can impact buildings in many ways. When the weight of the snow on the roof of a building approaches or exceeds its original design capacity to withstand heavy snow conditions, a condition of snow "overloading" is reached that poses risks for building roof collapse and the safety of building occupants and critical assets that are part of a building (e.g., communications equipment). In addition to increased risks for collapse of roofs, snow on the roof can cause water leakage (from ice dams) which can lead to structural concerns and health risks from mould as well as slip and fall hazards near the building. An abundance of snow around buildings can also lead to increased snow removal expenditures and hinder access to and egress from buildings, access to water and sewer services, and building maintenance.

0.2 Overview

This Standard is intended to be used to establish ongoing practices to reduce snow overloading risks over the lifespan of the building, which include pre-season roof snow removal planning and building maintenance to reduce risks of collapse and extend the life of the roof.

In addition to the assessment and removal requirements outlined in the body of this Standard, a series of Annexes have been included to provide additional information and templates for the user.

To assist in application of this Standard, a snow load assessment flowchart has been provided in Figure 1.

Scope

1.1 General

This Standard provides

a) maintenance procedures to reduce snow overload risk on existing buildings;

b) monitoring, detection, and assessment methods for snow load risks on buildings; and

c) procedures for snow removal.

1.2 Exclusions

This Standard does not address

a) specific requirements for the design or construction of new buildings subjected to snow loads; or

b) requirements for the structural rehabilitation or decommissioning of buildings subjected to critical snow overloading risks.

Note: Although provisions in the building codes apply for new design, Annex F provides supplementary background information on climate change and its implications on the design and retrofit of buildings.

1.3 Terminology

In CSA Standards, "shall" is used to express a requirement, i.e., a provision that the user is obliged to satisfy in order to comply with the standard; "should" is used to express a recommendation or that which is advised but not required; "may" is used to express an option or that which is permissible within the limits of the standard; and "can" is used to express possibility or capability.

Notes accompanying clauses do not include requirements or alternative requirements; the purpose of a note accompanying a clause is to separate from the text explanatory or informative material.

Notes to tables and figures are considered part of the table or figure and may be written as requirements.

Annexes are designated normative (mandatory) or informative (non-mandatory) to define their application.