To many a residential developer, both for-profit and nonprofit, multi-family, multi-story modular construction has become as tempting as candy at a supermarket checkout to a toddler waiting in line. Evangelists for modular preach its lower cost, its supposed “greener” fabrication, the speed of its installation. Modular units come not just framed and sheathed, but with plumbing and wiring installed, and usually with their interiors finished all the way through paint, flooring, and cabinets.

We in the Building Trades have our own objections to modular construction. It moves jobs away from local jobsites and to factories that can be far distant, even overseas. One San Francisco developer and modular evangelist, Patrick Kennedy of Panoramic Interests, has repeatedly called for importing modular units from China for midrise buildings to house the homeless.

The San Francisco Building Trades have taken into their ranks enough workers from China to have great confidence in their skills and ethic. We are not nearly so confident that employers there will let them build a product that is safe and of high quality.

Kennedy and his fellow evangelists fail to mention a feature that may be an advantage to developers, but a hazard to modular units’ occupants, their owners, and the cities in which they are piled.

At the request of Commissioner Debra Walker, San Francisco Department of Building Inspection (SFDBI) staffers gave a presentation on building standards and inspection for modular construction to the June 15, 2016 meeting of the Building Inspection Commission.

They told the Commission that in most regards modular construction is subject neither to San Francisco building codes nor to San Francisco inspection. SFDBI can inspect foundations, common areas, building exteriors, and exterior connections for plumbing, sprinklers, and wiring, they said, but not the contents of walls, floors, or ceilings, or even the interiors of units. They can inspect how the boxes are stacked, but not what is in them. They cannot question just what chemicals have gone into paint or into flooring adhesives. More than that, the SFDBI staffers said that sometimes modular units are inspected by “third-party” inspectors – which we can understand as inspectors not directly responsible to any public agency responsible for the public good.

San Francisco is a city of close-packed wooden structures in one of the most seismically active regions on earth. No other city in this country is built quite like it. Its Fire Department recognizes its vulnerabilities, and takes a more aggressive approach – and one riskier to its firefighters – to fighting fires than almost any other fire department. Its Building Inspection Commission and Board of Supervisors also recognize them, and our building standards are more stringent than California codes.

The use of modular construction introduces a weakness into the City’s building stock that would not otherwise exist.

It brings other hazards. SFDBI staff pointed out that if ever an owner wants to remodel or needs to repair a modular property, everything will have to be brought up to local code. The up-front cost savings of modular construction could well be obliterated by later expenses, perhaps conveniently to a developer or owner who has sold and moved on, but to the chagrin of the present owner.

The Building Inspection Commission President, Angus McCarthy, in discussions at the June 15 hearing discerned another hazard: Allowing substandard construction like modular is unfair to developers and contractors that build to San Francisco standards. If modular construction proliferates, it will make it harder for developers and contractors that do build to our requirements to compete for projects, financing, and buyers. The effect could well be to accelerate substandard construction. San Francisco’s building codes would become more and more meaningless.

The state legislature should pass legislation that allows local jurisdictions with stricter building codes like San Francisco to apply those codes to modular construction inside and out and to require inspection by their own inspectors, accountable ultimately to their own residents. If that means sending those inspectors to factories as far away as China, then so be it, and the expense should be borne by the developer or contractor that has chosen the product and its manufacturer.

But we are entitled to doubt that the state legislature will pass any such legislation. Most of the districts state legislators represent build under the same codes as does modular. No one else has quite the same building challenges and perils as San Francisco. Sprinkle a few pinches of developer money into the stew, and legislators will have more appetite for voting against than for such legislation.

San Francisco might not be able to prohibit modular construction, either. To do so might even run afoul of the interstate commerce clause of the United States Constitution.

Business – developers included – often tout market solutions to such challenges as housing affordability. So-called solutions can prove to be problems when buyers or tenants don’t really understand the products the market offers.

What San Francisco – what we in the San Francisco Building Trades – can and must do is educate buyers and tenants just what they are and are not getting with modular construction.