The inevitability of residential prefabrication (Part 2)
Wood frame panelization cuts time on the site, and more
April 19, 2018 by John Bleasby
Say “prefabricated” or “modular” housing and you might think of small, rectangular homes built in a factory and hauled down the highway on massive trailers. However, that isn’t the tip of the iceberg of what these terms mean today. In fact, the term ‘panelization’ better describes the direction more and more home builders are turning. Panelization of one sort or another is seen by many industry leaders as the best path forward when dealing the big-picture factors covered in Part One of this series — the challenges of skilled trade labour shortages in the future, Net Zero Energy requirements and associated costs, and overall housing affordability.
What is panelization?
It’s basically one of two things; either wood framed wall, floor and roof assemblies, or Structural Insulated Panels (SIPs). First, let’s look at the wood frame panelization concept. In many ways it’s the easiest transition from the popular on-site stick construction method without the challenges of turning to a completely new building format.
Efficiency gains at all levels
You’re probably using factory-built roof trusses already. Well, imagine all the interior and exterior wall sections and full floor systems built the same way, made-to-measure in a controlled factory setting in a matter of days. In this factory setting, skilled trade workers focus on specific tasks. Accuracy, material quality, and consistent quality are made possible by the use of the latest in machinery and technology. These are the advantages of turning to a panelized approach. Workers in this controlled setting also perform better, reducing human error. At the site itself, full sections are delivered on a flatbed, lifted into positon by crane. In a matter of days, the basic framework of the new home is in place and closed in. Labour costs are reduced on site, meaning contractors might be able to handle more projects concurrently by splitting their single current larger crew into two separate crews, each handling a different build project.
Toss away images of modular homes in limited designs
Today’s panel manufacturers use CAD design programs that send specifications directly to shop floor. There, precision cutters turn the home’s design into a series of ready-to-assemble sections in a matter of days. Even variances associated with local building codes can be taken into account before the assemblies leave the factory. For a contractor dealing with unpredictable time losses and material delays due to the raucous Canadian climate, this level of quality, on-time delivery, and assembly time assurance means more efficient use of the labour, reduced costs, higher profit potential, and happier clients.
How to properly calculate the total savings of panelization?
Panel manufacturers benefit from volume purchase discounts of materials versus a contractor who custom orders from a lumber supplier as needed. Still, the upfront cost of panel systems can be as much, even a bit more, than on-site stick construction. Some estimates put the cost premium at fifty cents per square foot. However, it would be simplistic to leave the discussion at that point. The cost savings realized over the full assembly of the project however must be considered. On-site waste, not only in the form of scraps left after cutting but also excess material resulting from over-ordering, rejected warped or imperfect materials that have to be returned, theft from the site, clean-up time that takes skilled tradespeople away from their work — it’s all time and money.
Need some numbers to help understand the advantages?
The Structural Building Components Association (SBCA) was established in 1983 as an international trade association representing manufacturers of structural building components. It brings together truss plate and original equipment manufacturers, computer engineering and other service companies, lumber mills, inspection bureaus, lumber brokers and distributors, builders and professional individuals in the fields of engineering, marketing and management.
The SBCA conducted a side-by-side study of a 2600 square foot house to compare time and costs for the completion of a frame home on a pre-built foundation (see below).
Why has it taken so long for panelization to take hold?
Prefabrication, modularization, even panelization, is not new. This is not the first time the concept has been promoted as the way of the future. However, given the pressures on the industry going forward, panelization offers the next logical step in the evolution of wood frame construction. Yet, studies by the Wood Promotion Council indicate that it only represents about eight per cent of the home building market. Why isn’t it more popular?
Prejudice, finger-pointing and resistance to change are hold backs
Certainly panelization has come a long way in a few years due to the development of more sophisticated factory set ups. However, what lingers like a nasty smell is the stigma associated with those flatbeds lugging small unattractive buildings down the highway, and quality assurance prejudices based on unhappy past experiences.
There is also the issue of change and training crews to move away from a framing mentality that at times appears almost cult-like and towards a new building process. There’s also the issue of garbage-in, garbage-out — contractors can waste time on-site and start losing efficiency benefits if the design isn’t conceived with panelization in mind, or if the dimensions submitted to the panel manufacturer are sloppy and imprecise to begin with. Adjusting factory-built panels is not the same as fixing measurements on-the-fly during stick construction.
Nevertheless, the savings through efficiency and the resultant profit gains are there for the taking, for contractors willing to adjust their processes to a new building reality.
Did you read the full series?
Part 1: Three factors that point to a dramatic change in the future of Canadian home building
Part 3: Structural Insulated Panels (SIPs) may be the answer for the residential housing industry
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