3D homes look ingenious, but their time will probably never come

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A recent TV report showed a prototype house in California being built using a large-scale 3D printer, visually a genius moment. A special nozzle on the end of a large robotic arm steadily tracked and extruded straight lines of material, layer by layer, to form the exterior walls of the house. The accompanying voiceover speculated on how this innovative technology could change the way we build, promising to drastically reduce the time and cost of building homes.

Well maybe not. The prospect of 3D printing a house, as ingenious as it sounds, is yet another in the long list of home building tech ideas whose time has not come and probably never will. It is also an idea that carpenters and masons may not appreciate.

Practicing home builders, architects, and engineers know that the labor and materials for the framing—walls, floors, roof—of a home is a small fraction of the total cost of a finished home. to be busy. Even if framing costs were cut in half, the total construction costs and selling price would be affected by an insignificant percentage, if at all.

This is not rocket science. Just think of everything you need beyond framing: windows and doors, insulation, plumbing and related fixtures, HVAC systems, cabinetry, appliances, and finishes. Add to that the cost of the land and its improvements: grading, excavation of foundations, connections to public services, landscaping.

Added to these costs are the multiple indirect costs to the homebuilder: regulatory processing and compliance related to rezoning and issuance of building permits; legal fees; interest on construction loans; Assurance; advertising and marketing; and project management and administrative overhead.

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The challenge for home builders is that an incremental cost saving in one element of direct home building can suddenly be offset and rendered inconsequential by unforeseen increases in other cost elements, direct and indirect. This undermines financial feasibility, happens often, and is in fact happening right now. Today, previously planned projects and budgeted construction costs are rising rapidly due to price inflation, supply chain issues and rising interest rates.

Clearly, all of these real and interrelated costs associated with real estate development and construction hinder innovation in home construction. As a result, demand is outstripping housing supply in many parts of the country, driving up house prices. And they explain why the production of affordable housing, whether for rental or sale, is becoming increasingly difficult, more expensive and more dependent on public subsidies.

To make matters worse, state and local growth and development policies, particularly zoning, limit housing types, residential densities, and mixed land uses in urban, suburban, and peri-urban areas. More flexible regulations would reduce unit land costs for housing construction.

These challenges are not new, just as technological exploration and invention are not new. There is a long history of efforts in the United States to study and address real estate and housing challenges, beginning in the early 20th century. I was part of such an effort 54 years ago as a co-author of a congressionally funded report titled “Roadblocks to Innovation in the Housing Industry.”

Our discoveries in 1968 have not changed. As today, major roadblocks then increased direct and indirect construction costs; the limited availability and cost of mortgage financing for both builders and home buyers; and limited land availability with high land costs due to restrictive zoning regulations.

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In the 1960s, factory-built prefab homes were seen as the technological innovation promising to save money and increase the supply of American homes. Factory assembly lines could manufacture houses at a very high rate. But factory production rates far exceeded the rates at which finished homes could be shipped and inventoried, subdivisions created, improved lots prepared, mortgages secured, and sales closed. It was clear that the barriers to innovation were systemic rather than technological.

Only the mobile home industry has managed to keep volume production of reasonably affordable prefabricated homes going. But caravan-style homes deployed in dedicated exurban mobile home parks cannot significantly meet the country’s residential needs.

The roadblocks reported to Congress 54 years ago remain and are still not technological. While eventually enabling the cost-effective manufacturing of some parts and building blocks, 3D printing technology is unlikely to do much to alleviate the persistent and systemic housing problems in the United States.

Roger K. Lewis is a retired architect and professor emeritus of architecture at the University of Maryland.

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