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This section of our “All About Modular” information hub is updated as questions are received. If you don’t find an answer to your question below, please contact CHBA’s Director, Modular and Construction Systems.

What do we mean by the term “modular” construction?

There are several terms that people use to describe the factory-based method of construction:

  • Factory-built
  • Industrialized
  • Modern Method
  • Offsite
  • Systems-built

Some of the terms are more common in different regions than others, but they are all used to describe the construction of homes and buildings that are wholly or partially produced in a factory, with installation, assembly and finishing completed on-site. There are a number of building systems that result in varying degrees of completion in the factory before delivery to the building site:

Is airtightness testing performed on modular homes?

Airtightness testing is routinely performed in factories as a quality check, and for demonstrating code compliance on-site where required. In some cases, authorities accept in-factory tests, for example for single-section homes that are placed on surface-mount foundations—these homes are complete when they leave the factory and the air barrier will not be penetrated during installation.

If a certified building is eventually altered or added to, would that building lose its CSA-A277 or CSA-Z240 MH certification?

Certifications apply only to the work that is completed in the factory. Any modifications performed or additions constructed on-site are subject to the usual requirements of local authority for site construction and renovation.

Is it correct that the scope of the NBC does not cover the construction using prefabricated modules and panels, since CSA A277 covers prefabricated “buildings, modules and panels” while Sentence applies only to “buildings”?

No, that is not correct. While NBC Sentence in Division A states that the NBC “applies to both site-built and factory-constructed buildings”, the appendix note to this sentence explains that “The CSA A277 standard is not a building code, only a procedure for certifying compliance of factory-constructed components with a building code or other standard.” In other words, even if Sentence only talks about the building code’s application to buildings, the code requirements in Division B address all kinds of building elements. When building elements are pre-fabricated and bear the label of CSA A277, they are certified to be code compliant to those requirements. So, by extension, the construction using prefabricated modules and panels is covered in the building code, because the individual requirements for building elements in the building code do not specify a location of construction.

For multi-family projects, would the individual modules have to be certified but the overall assembly of the building would still require professional involvement and standard code/permit process?

Yes, professional involvement is required as usual for multi-family. Certification covers only the work done in the factory; work done on-site is subject to usual inspections.

Do certification labels have a serial number?

Yes, and the CSA A277 certification procedure requires that the construction information for the unit associated with the serial number is kept for a minimum of five years.

What is the best way for doing factory review of the modules? Is there a QA checklist template?

Yes, the factory process uses checklists and testing logs that travel with the modules along the production line.

Can a factory in one province or territory build homes to be installed in another province or territory?

Yes, factories may be certified for delivery to more than one province. For example, a factory in Ontario could deliver homes into Québec that comply with local code requirements, and vice-versa.

Are modular buildings from other countries also certified under the CSA A277? Would they have to use material that is certified in Canada?

All buildings installed in Canada must meet the local building codes where they are installed. Buildings constructed outside Canada are not exempt, and all the requirements apply. Factories in other countries can be certified to the requirements of the CSA A277 standard to be eligible to deliver buildings, modules and panels for installation in Canada.

What about project-specific requirements like fire stopping, how are these details confirmed?

A designer in the factory studies codes and project specifications and provides construction drawings and documents to the factory floor. The testing log and checklist that travels with the building in the factory through each station will ensure that the details are built as specified.

Are the design documents (the ones kept for a minimum of five years) available to building officials?

Yes. You could contact the factory identified on the certification label.

Things like spatial separations (9.10.15 of the code) would be of interest to the local building inspector. Would this fall to the manufacture to ensure prior to delivery? Are these items covered in the standard?

Yes. The factory is aware of the lot size and limiting distances for construction of the exposed building face and they would be taken into consideration in the factory. The CSA A277 standard is not a technical standard. It is a procedure for “demonstrating compliance to all local codes and standards”. The certification body makes sure that the procedure in the factory will result in homes and buildings that are compliant with local requirements.

Is the plumbing system tested prior to the drywall being installed so leaks can be easily detected and corrected?

Yes, plumbing system leak tests and pressurization tests are done more than once, and before the walls are finished.

Are the manufacturers verifying the performance ratings for water resistance and energy ratings for fenestrations as well as subsill and head flashings?


Reduced Greenhouse Gas Emissions

Section 9.19. exempts factory construction from the requirement for attic ventilation. The phrase  “Except where it can be shown to be unnecessary” is explained in the Appendix note as “The exception provided in Article recognizes that some specialized ceiling-roof assemblies, such as those used in some factory-built buildings, have, over time, demonstrated that their construction is sufficiently tight to prevent excessive moisture accumulation. In these cases, ventilation would not be required.”


For more information contact:

Keith Herring

Keith Herring

Modular & Construction Systems
613-230-3060 ext.261