The minimum specified Snow load has increased.
The Current 1995 National Farm Building Code of Canada is REDACTED
The current Canadian Farm code is going to be redacted as of January 1, 2025. Replacing it is the National Building Code of Canada Part 2: Farm Building. The new code has changed the minimum snow loading required on greenhouses, from 700 Pa to 1000 Pa. This change is arbitrary, not backed by any rationale or evidence, and is higher than the normal design snow load for some areas in Canada including Leamington.
Speak up for Change: Submit your request today to reduce the snow load on greenhouses!
Follow our template and make a difference in 5 steps. https://cbhcc-cchcc.ca/en/code-change-request-form/
Step 1
Visit https://cbhcc-cchcc.ca/en/code-change-request-form/ .
Fill in your personal information.
Step 2
Select your function(s). Pick all that apply.
Step 3
Code Change
To the existing code provision
Document
2020 National Building Code
Code Reference
2.3.3.2
Subject
Snow Melt Provisions for Greenhouses
Problem
The clause gives no guidance on how a reduced snow load may be calculated and the minimum is 43% greater than the 1995 NFBCC
Proposed Modification
In a farm building classified as a Group G, Division 3 major occupancy where hearing and drainage systems are installed to prevent the accumulation of snow and water, the supporting structure for the light-transmitting roof areas is permitted to be designed for a specified roof snow load using the following formula
S = Is*(Cb*Cw*Cs*Ca*Cm*Ss)
With a snow melt factor, Cm, of 0.85 providing a minimum specified snow load of 300 Pa.
Justification
Adopting the proposed change provides a consistent application of greenhouse roof specified snow load. This approach considers the relative to the ground snow load for the location of the greenhouse, allows for a reduction based on melting of snow which has been researched in adopted in the ASCE 7, and NEN13031 codes, and provides a safe design value. The current minimum specified snow load value of 1000 Pa is higher than the normal design snow load for some areas in Canada, resulting in a higher cost of construction where not necessary. On the contrary, the current minimum specified snow load value of 1000 Pa is lower than the normal design snow load for some areas in Canada, resulting in a potential structural risk of being under-designed.
Step 4
Which of the Code's Objectives does the requested change address?
Select 2020 NBC
OS2 Structural Safety
Step 5
Impact Analysis
No Additional Cost are associated with the proposed change. Yes, it will provide benefits that are measurable including in some cases reduced construction cost, and in other cases increased structural safety and integrity. The current provision (change from NFBCC 1995 to NBC Part 2) entails added costs to construction.
Enforcement Implications
The proposed changes will not affect enforcement implications. Yes, the requested change can be enforced by the existing building permit application review process. There is no requirement for an increase in resources.
Other Comments
See also CBHCC change requests 1825 and 2401
Contact Us
Better yet, see us in person!
GS Engineering Consultants Inc. has been serving the Greenhouse industry since the late 1990s. GSE has been in the forefront of the greenhouse industry, providing structural engineering services to many fabricators both domestic and international. Our knowledge includes the Canadian, US, and, EU Standards. Over the years GSE has developed a superior practice for the design of greenhouses recognized in many jurisdictions.
GS Engineering Consultants Inc.
2080 North Talbot Road, Oldcastle, Ontario N9G 0B8, Canada
