Is Prefab Right for You?
Updated: Oct 6, 2019
In the past, Prefab Houses (a house built in a factory and delivered to the site) have been synonomous with cheap and unimaginative structures. While there is some truth to that, there have been many notable exceptions. As mass production was perfected for consumer products, it was natural for architects to imagine the same techniques for housing.
Frank Lloyd Wright created an ingenious system way back in 1916! The houses, (shown left) are a far cry from how the image of prefab as unimaginative boxes. Thirty years later, post war, many architects designed compact, open plan contemporary housing for the baby boom. Many interesting ideas were documented in the Case Study House Program (worth checking out the 3D animated walk-throughs). Some designs took advantage of the post-war aluminum and steel manufacturing capability, using materials and shapes borrowed from the aerospace industry. However, since the 1970s, most of the innovative designs were pushed aside by cookie-cutter homes whose ambition was to provide a less expensive version of a conventional house.
The last decade has seen a resurgence of innovation in prefab housing, driven by the high cost of site-built construction and advances in manufacturing techniques. There are currently a wide variety of contemporary prefabs available.
Two Types of Prefab
It’s important to understand the two types of prefabs. Factory-built, modular homes come largely assembled complete with doors, windows, flooring, tile, fixtures, etc already installed. They are assembled from 15’ wide modules, delivered by truck and assembled with a crane in a few days.
Panelized homes are built on-site from pre-manufactured components including sections of walls, floors, roofs, etc. These homes do not generally include the finished interiors, which are site-built. Companies such as Deck House (Acorn) and Lindal Cedar have been building these homes for many years in New England.
Is Prefab a Good Idea?
There are a lot of good arguments for prefab- it is more energy-efficient to build in a factory versus on-site, and produces far less construction waste. The quality control can often be better than site-built (would you prefer a car that was built in a factory, or assembled in your garage?). The materials are assembled in a climate-controlled
environment, rather than being subject to the vagaries of New England Weather. They can also be far quicker to build, which reduces costs associated with financing, etc. With all that going for them, why not choose prefab for your home?
Cost- Strangely, prefab is often not less expensive than site-built. Transportation and specialized assembly crews can offset some of the initial savings. But the main issue is the cost of customization. Assembly line-produced objects are cost-effective because they are all the same. If you wanted a car that was three inches longer than what was available, it would cost millions of dollars to make that change. To a lesser extent, prefab homes are the same. The cost benefit comes from the standardization of parts and processes, and deviating from these slows down the line and adds to the cost.
This problem of customization leads to the largest problem with prefabs- they are not designed specifically for your site. Typically, clients ask architects to design a home to address their living patterns, aesthetics, and the specifics of the building site. Good design is always a response to the site, whether it is orienting the house towards a particular view, for solar exposure, or to relate to nearby features (houses, trees, streams, etc). Modular homes do not generally allow for customization, other than site orientation. Panelized homes offer more customization, but again the details are limited by the components that are offered. For example, a company may not be willing to substitute steel beams for wood, or use a different type of multi-slide door.
In every case where I have designed a custom home and priced it out as a modular or panelized home, the cost was greater than having it site built. It’s probably true that if I had designed from the outset within the limits of the prefab production options, the price may have been better. But in the end, most of my designs feature custom forms and details that are not conducive to off-site prefabrication.
Prefab is a greater solution to the problem of affordable housing, and if adopted on a large scale would increase energy efficiency and decrease waste in the construction industry. Whether it is the best solution for your particular house will be determined by your budget, your desire for customization, and the particulars of your site (for example, the roads leading to your site must be wide enough to accommodate an oversize tractor-trailer).