Prefab: Not What You Might Think
Updated: May 9, 2019
There are lot of misconceptions out there - learn below what this technology is, and isn't.
You've likely heard some of the buzz around prefabricated buildings recently. There are many new and innovative construction projects attracting attention, but still a great deal of misunderstanding about what prefabrication really is. Terms like factory built, modular, and prefab are often misused. Below we provide an overview of what prefabrication really means.
What Prefab Is
Generally, prefabrication can be viewed as any component of a construction project that is built off site. Typically this prefabrication will take place in a factory, or controlled environment out of the damaging impacts of the elements. Once the prefabricated component is finished, it is transported to site and integrated into the larger project. Prefab tends to be associated with a finished building, but it is better to consider as a spectrum. Even the most 'traditional' site builds will typically use some degree of prefabrication. Roof trusses for example, are often built off site, then delivered and placed on the wall framing. On the far other end of the spectrum we have modular construction, a form of prefabrication where nearly all of the building is constructed off site in large pieces (modules) before being transported to site and placed on the foundation.
These are two examples of prefabrication at different ends of the spectrum, but there are also many solutions in between. Other examples of factory built components include panelized systems, prefabricated steel or timber frames, and precast concrete. As described above, these items are produced in a controlled environment before being shipped out and installed on site. While there are benefits to prefabrication (protection from the elements, quality and time improvements, etc.) potential drawbacks include factors like transportation limitations and design constraints. The best method to build will be determined by your unique project.
It's worth noting that even projects with a high level of prefabrication will require a degree of site work. In this sense most projects are hybrids, and take advantage of the best of both worlds.
What Prefab Isn't
As alluded to above, prefabrication is not a type of building, or end product. The quality of any build, constructed on or off site, will largely depend on the contractors and trades building it. Specifically when considering prefabrication, one very important distinction to make is the code standard used.
In Canada for factory built structures we have CSA A277 and Z240 classifications. These are very different standards. The CSA A277 classification is not a code, but rather a certification that a building is constructed to the applicable national, provincial and municipal codes. CSA A277 buildings are built to the same code that every site build must comply with. The CSA Z240 classification on the other hand, is a separate building code in itself. This code is not equivalent to the National Building Code standards, and is limited in where its use is permitted. This is essentially a mobile home or trailer.
For all factory built construction, CSA inspectors visit off-site facilities to certify that components are code compliant (much like local site inspectors who check for code compliance throughout a site build). In addition, once the structure is fully installed on site, local inspectors resume their duties, giving final inspection and occupancy.
Now that you are a little more familiar with the basics of prefab, what type of construction is right for your project?