Date of Publication: June 30, 2025 [2022.02.V-02.C]
Subject: Definition of Crawlspace 2024 OBC Update
Summary of Updates: No changes to recommendation or references.
2024 Ontario Building Code [O.Reg 163/24 Amended to 5/25] Reference(s):
1.4.1.2. of Div. A
3.2.2.9. and 9.10.9.4. of Div. B
3.1.11. and 9.10.16. of Div. B
3.1.4.2. and 9.10.17.10. of Div. B
9.18. of Div. B.
Incoming Request:
Often designers and homeowners submit permit drawings that include a space labelled as a “crawl space”, without providing sufficient information as to the actual use or intended function of the space (or additionally labelling an area as “storage crawl space”). There tends to be varying opinions on what the purpose of a crawl space is, as it relates to Code regulations, particularly with respect to fire protection and the intended purpose of the permitted exemptions that are offered to a crawl space. A common question posed is “Can a crawlspace be used as storage?”
Executive Summary:
Crawl spaces are not a defined term in the OBC, however the Code places many limitations and requirements on spaces identified as crawl spaces. A definition is proposed that will assist building officials and designers in determining what spaces can be considered as crawl spaces. Building officials and designers need to be aware that storage is generally not permitted in a crawlspace.
Discussion & Considerations:
Definition of Crawl space:
The term crawl space is not defined in the building code and so it is assigned it’s common and ordinary meaning within the context of the building code regulations. A crawl space is commonly understood as “an area or space of limited height under a floor or roof, giving access to wiring and plumbing”, however, further consideration is needed to define the term within the context of the Ontario Building Code.
When reviewing the Code, both Part 3 and Part 9 are consistent in identifying the characteristics of a crawl space, as it relates to certain exemptions applicable to a crawlspace. These main characteristics are noted below:
- There is a height of 1.8 m or less at any point within the crawlspace, measured between the lowest part of the floor assembly and the ground or other surface below,
- Does not contain an occupancy, whether a major occupancy or a subsidiary occupancy,
- There are no flue pipes passing through the space (refer to definition of flue pipe),
- The space is not being used as a plenum in combustible construction (refer to definition of plenum).
If the space being identified as a crawl space is exhibiting these criteria, then it may be considered as a crawl space and enjoy such permitted exemptions that include but are not limited to:
- No fire separation required for the floor above the space,
- Protection of foamed plastics not required if the space is concealed from other spaces,
- Not required to be considered a basement as defined by Div. A 1.4.1.2, and required by Div. B 3.2.2.9. and 9.10.8.9.,
- Only requires an access opening (size per 3.6.4.6. or 9.18.2.1.),
- No requirement for stairs to access the crawl space (ladder access is acceptable),
- May be ventilated by natural or mechanical means,
- No minimum required ceiling heights, except for clearances to access service equipment.
Limitations of Crawl Spaces:
A storage use is considered as an occupancy under the definition of occupancy and industrial occupancy, and thus would not be permitted within a space defined as a crawl space for the purpose of the fire protection requirements/exemptions of the Code. The use as storage creates potential for fire hazard, whether low fire load or high fire load. This is consistent with Div. B 2.4.1.1.(3) of the Ontario Fire Code, made under the Fire Protection and Prevention Act, requiring that crawl spaces shall not be used for storage of combustible materials.
The exemptions of fire separations for crawl space floors confirm that crawl spaces are of a limited height of maximum 1.8 m. Additionally, there may be scenarios where a crawl space falls within the parameters of section 9.18., with a height not more than 1.8 m, but that do not meet the conditions for waiving of the fire separation under Div. B 3.2.2.9. and 9.10.8.9. if it used as a plenum in combustible construction or for the passage of flue pipes.
The requirements for fire blocking, and the definition of horizontal service space both confirm that a crawlspace is comparable to that of concealed spaces in walls or floors, in that they are voids within the building used for building services, such as chutes, ducts, pipes, shafts or wires, and that are generally inaccessible and not specifically an occupied part of the building.
While article 9.18.4.1. implies that a crawlspace is permitted to contain building service equipment, it is important to recognize the limited nature of a crawlspace, and the distinction between it and a service room which is an occupiable room within the building. A crawlspace should generally contain a limited amount of service equipment and maintain the characteristics of being generally inaccessible and unoccupiable. If the space is considered a service room, it may require fire separations to separate it from the remainder of the building if serving other than an individual dwelling unit.
Risk/Benefit Analysis:
The OBCAS feels that this is a low-risk interpretation that provides the benefit of harmonization with the Fire Protection and Prevention Act regarding assessment of risk in a crawl space and will create consistency for Building Department and Fire Prevention Officers for adequate enforcement of life and fire safety requirements by both Codes.
Final Recommendation:
To clarify permitted uses of the space and what parts of the OBC apply to it, building officials should consider using the following definition for crawl space:
“Crawl space means an area or space under a floor that has a limited height that does not contain an occupancy or storage use, and may contain or provide access to building services and equipment.”
With the above considerations taken into account, it is important for building officials and designers to understand that a crawl space has limitations. By utilizing the OBCAS definition it will better allow a plans examiner to properly identify and review plans in a consistent manner.
During plans review, a building official should consider asking the applicant any relevant questions related to the space, or even make red-line notes to the plan to clarify items such as “no storage permitted”, to avoid crawlspace design issues being found during construction. If the space contains any building service equipment, serving other than an individual dwelling unit, it would be prudent of the plans examiner to have the building designer confirm through design rationale that the amount of equipment is limited in nature, and does not present a fire hazard by not being within a service room enclosed by fire separations, (where applicable).
Referenced Documents:
1. The functional statements and objective statements of the Code, as referred to at the top of this document.
2. Ontario Fire Code – Div. B 2.4.1.1. Accumulation of combustible materials
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.