Date of Publication: September 28, 2026 [2026.09.V-01.C]
Subject: Professional Design and General Review for Farm Buildings
2024 Ontario Building Code Reference(s):
Article 1.3.3.1A. of Div. A
Article 1.4.1.2. of Div. A
Part 2 of Div. B
Subsection 1.2.2. of Div. C
Appendix A (various notes)
Incoming Request:
For a single-storey, 1000m2 (gross area) building with only an agricultural occupancy, what parts of the design require professional design and general review by an architect or engineer?
Executive Summary:
Farm buildings are now defined by the new Group G major occupancy types. Part 2 governs their construction, and most farm buildings over 600 m2 in gross area or over 3 storeys in height require professional design and general review for the building and its building systems.
Discussion & Considerations:
Background:
Before the 2024 OBC, farm buildings were defined by their location (on “land devoted to the practice of farming”) and their use (no “area used for residential occupancy” and used “essentially for the housing of equipment or livestock or the production, storage or processing of agricultural and horticultural produce or feeds.”). Farm buildings were required to conform to the National Farm Building Code of Canada, with some exceptions. The NFBCC contained unclear (and now outdated) references specifying conditions under which professional design and review was required, so many authorities having jurisdiction (AHJs) did not require professional design and review for farm buildings.
The 2024 OBC introduced a new definition of farm buildings, which is based on a new major occupancy classification (Group G, Divisions 1 to 4) for agricultural occupancies. It also introduced Part 2 (Farm Buildings), which applies to buildings “more than 600 m2 in building area or more than 3 storeys in building height” containing an agricultural occupancy.
However, Article 2.1.2.2 states that “Buildings or parts of buildings containing an agricultural occupancy that has an occupant load of more than one person per 40 m2 shall be classified according to their major occupancy as belonging to one of the Groups and Divisions listed in Table 3.1.2.1. of Division B.” While neither the agricultural occupancy classification nor the definition of farm building limits occupant load, it appears that Part 2 applies only to buildings with an occupant load of not more than 1 person per 40 m2.
General Review Requirements:
In the 2024 OBC, Table 1.2.2.1. of Div. C has been updated to reflect that buildings containing an agricultural occupancy that are more than 3 storeys in building height or more than 600 m2 in gross area require general review by an architect or engineer.
Professional Design Requirements:
The OBC does not dictate requirements for professional design, which is regulated by the Architects Act and the Professional Engineers Act. Although an AHJ does not enforce either Act, s.8(2)(b.1) of the Building Code Act allows a CBO to refuse to issue a permit where a design has not been prepared by an architect or engineer if the respective Act requires it.
The Professional Engineers Act includes agricultural occupancies in Section 12 where the Act describes buildings that must be designed by a professional engineer. The Architects Act has been similarly updated (Section 11) to include agricultural occupancies. Without an exhaustive analysis, the Architects Act and the Professional Engineers Act both require a building greater than 3 storeys or greater than 600 m2 in gross area to be designed by an architect or a professional engineer (see the respective Acts for details). The PEO/OAA Joint Bulletin: Design and General Review Requirements for Buildings in the Province of Ontario has not yet been updated to include agricultural occupancies.
One exception to the above is that Sentence 2.3.1.1.(4) requires only that any subsurface investigation be carried out by a “suitably qualified person”, either before or during construction. This contrasts with Sentence 4.2.2.1.(1), which requires the investigation to be done by a professional engineer.
Design of Specific Systems:
The OBC does not differentiate between systems (i.e., structural, electrical, mechanical, and fire prevention) when spelling out general review requirements. Where general review is required for a particular building, it is reasonable to apply that requirement to all the “building systems” in the building.
Likewise, the Architects Act and Professional Engineers Act do not specify which building systems require professional design. While agriculture-specific systems such as automatic milking, feed conveyance or nutrient transfer systems are exempt from OBC regulations (similar to industrial process systems in an industrial use), other typical building systems such as heating, ventilation and air-conditioning (HVAC), lighting and power supply would fall under the jurisdiction of the OBC because they are essential to the function of the building.
Certain building systems are specifically referenced in Part 2, which refers to other parts of the Code: Subsection 2.3.1. directs the reader to Part 4 for design of structural systems, and Subsection 2.4.1. directs the reader to Part 6 for design of HVAC systems.
Overall Impact of the 2024 Code:
The inclusion of Part 2 and the creation of Group G agricultural major occupancies have in effect made farm buildings “real buildings”. These buildings and their associated systems are subject to design and general review requirements (with some exclusions for small farm buildings and buildings of no human occupancy) in the same manner as other buildings.
As noted earlier, buildings containing a Group G major occupancy with an occupant load greater than 1 person per 40 m2 need to be reclassified per Table 3.1.2.1. and moved into Part 3 or Part 9, where the requirements of those parts apply.
Historical Context & Implications:
As noted earlier, interpretation and enforcement of professional design and review requirements for farm buildings were inconsistent before the 2024 OBC. The introduction of Part 2 in the 2024 OBC has clarified the requirements.
However, the farm building industry may not have fully grasped the extent of these new requirements. Although a municipality may be well within its jurisdiction to require professional design and general review, there may be significant initial resistance from farm owners, designers, constructors, manufacturers and other stakeholders.
Final Recommendation:
AHJs should clearly communicate their expectations regarding professional design and general review of farm buildings. Where objections to professional design are raised, referral to the OAA or PEO for clarification may be helpful.
Recommendation to Ministry of Municipal Affairs and Housing:
A joint information package from MMAH, the Ministry of Agriculture, Food and Agribusiness, and other stakeholders, clearly outlining these changes, would be helpful.
Referenced Documents:
2024 Ontario Building Code O.Reg 163/24 Amended to 05/25
Disclaimer:
This guidance document is intended to assist building officials by gathering relevant information to interpret the OBC Act and the prescriptive requirements of the Ontario Building Code, and is intended to be a best practice aid for building officials.
The views expressed within this guidance document should not be considered as the official interpretation of legislated requirements based on the Ontario Building Code, as the final responsibility for interpretation rests with the local Authority Having Jurisdiction.
The views of this advisory committee should not be construed as legal advice.