HALDENSTEIN.- A list of 10 “Working Rules” is taped to the concrete wall on the top floor of Swiss architect Peter Zumthor’s studio, which overlooks a dramatic alpine landscape through floor-to-ceiling glass. Rule No. 1: “Have a clear idea of what you want.”

I had a clear idea. Several months earlier, at a dinner following a talk he gave at Yale, Zumthor had told me almost offhandedly that his experience designing a new wing for the Los Angeles County Museum of Art, now under construction along Wilshire Boulevard, had been so trying that he’d decided he would never work in the United States again.

I wanted to hear more about his experience — and what other lessons the architect had drawn from his first American project. Plans for the new wing, known officially as the David Geffen Galleries, for its lead donor, have attracted intense criticism, dividing the world of Los Angeles art and architecture like no other in recent memory.

“LA was tough,” Zumthor acknowledged when we met at his office in Haldenstein, Switzerland, population 1,000, a village about 70 miles southeast of Zurich. We sat down inside the taller of his firm’s two studio buildings, which holds drawings and a series of models of the LACMA project as well as plans for a compound Zumthor is designing for the Qatari ruling family and, on a nearby shelf, a coffee mug reading “Best Boss Ever.”

On the question of why he didn’t think he’d work again in the U.S., Zumthor at first cast his answer in a positive light. He praised his work with LACMA’s director, Michael Govan, and with Skidmore, Owings & Merrill, the collaborating architect on the new building, which is designed to hold LACMA’s permanent collection.

“I couldn’t hope for such a good team again,” said Zumthor, who turned 80 in April. “I would be afraid. I think we’re lucky on this building, with Michael, with SOM.”

His responses to other questions were less guarded and more searching. Over the course of an 80-minute conversation, Zumthor repeatedly emphasized the ways in which the Geffen, a concrete wing spanning Wilshire Boulevard, has been simplified and stripped down. “There have been tough moments, when we had to reduce, reduce, reduce,” he said.

Complications with the building’s foundation, as well as the discovery of fossils on the site, have delayed construction by roughly a year. According to Govan, this has pushed total building costs for the new wing to $715 million, from a projected $650 million, forcing the design to be streamlined to keep it from going higher still.

It struck me that Zumthor was trying to prepare the Los Angeles public for a straightforward, even austere final product, without the precise and sometimes obsessive touches that give his best-known projects, such as the Kolumba museum in Cologne, Germany, an unusual combination of tactility, elegance and brawn.

Referring to LACMA’s foundation, Zumthor said, “They had to double it in some areas, because this was so soft, the tar in the earth.” Govan asked him to streamline the design, he added, “to compensate for all these millions of dollars for all these new (foundation) poles, without going to LA County,” which is paying for about one-fifth of the cost of the new wing. “If we were to go to the county to ask for such an amount, he knew they would say, ‘Let’s cancel it.’ So this we had to avoid.”

He described the gallery spaces as simple and unadorned concrete: “Essential spaces, like factories or something.” He added, “We did other things, like I abandoned most of my door details. There are no door details. We have the openings, but they’re just openings.”

This raised an obvious question: After all that simplifying, which elements of the LACMA building will be recognizable as Zumthor details?

“There are no Zumthor details any more,” he said flatly.

Govan, reached by phone, was — not surprisingly — quick to challenge that idea.

“No, no, that’s not true,” he said. “I would argue that there are many, several, Zumthoresque details.” He cited the metal handrail on the new wing’s largest staircase — whose final proportions he said Zumthor had been “fussing, fussing, fussing over” — as well as a floating steel door for fire egress, which according to Govan resembles a design element in Zumthor’s 2016 Allmannajuvet Zinc Mine Museum in Norway.

He acknowledged that Zumthor — who is the son of a cabinetmaker — had been forced to adjust his typical working method to accommodate the realities of building in the U.S. as well as the project’s shifting budget. “I used to joke with him,” Govan said, that while designing his European projects Zumthor “would go to the farmer in the next village, and find a cow, and they would tan the leather, and they would wrap the leather around the door handle of his building. And I’m like, ‘We’re not doing that.’ ”

Govan says the Swiss architect was one of the first people he called after becoming LACMA director in 2006. He announced in 2009 that he had engaged Zumthor to design a new wing replacing LACMA’s original 1965 campus of buildings, by William Pereira, as well as an addition from 1986 by Hardy Holzman Pfeiffer Associates. Zumthor was hardly unknown at that point: He had won the Pritzker Prize, architecture’s top honor, that year. But he had never worked in the United States, and never at anything close to the scale that the giant Los Angeles project required.

Early versions of his design called for an ink-black structure, with the fluid lines of a Jean Arp collage, on the north side of Wilshire, cantilevered over the edge of the La Brea Tar Pits next door. After the Natural History Museums of Los Angeles County, which oversees the tar pits, cried foul, concerned that the new wing would endanger ongoing paleontological work, Zumthor’s proposal evolved, in a slow-drip process, through several phases; it became, finally, a 347,500-square-foot building of gray poured-in-place concrete, unpainted and without pigment, that will span the boulevard. One end will touch down on the far side of Wilshire, on a parcel owned by the museum that had been used as a surface parking lot.

The galleries will be contained on a single level, lifted above the city on seven thick structural legs. (In addition to stairs and elevators, the legs themselves will contain a restaurant, a bookshop and a 300-seat auditorium south of Wilshire, among other elements.) This horizontality has been key to Govan, in particular, who has called it a more democratic way of organizing a collection like LACMA’s than stacking galleries vertically, with some artworks tucked away on higher floors that relatively few visitors ever reach.

“I had, if I can say so, a beautiful idea at the beginning,” Zumthor said. “I think we called it the black rose. This worked really well. And once I had to cross Wilshire, and use the other side, stakes got considerably higher.”

The Geffen building broke ground in 2020. Following those construction delays, it is likely to be completed near the end of 2024. The time necessary to install the art and otherwise prepare the building for visitors means the Geffen wing may not open fully to the public until 2026. The museum announced in August that it had reached its campaign goal of $750 million and said that work on the new building was 65% complete. In October of 2022, those figures were $700 million raised and 50% complete.

Zumthor describes the wing as “a concrete sculpture,” with floors, walls and ceilings of exposed concrete. There will be bronze surrounds on the window and door openings throughout the building. When I visited Haldenstein, he and his colleagues were weighing final choices for the color palette of the walls at the base of the new wing, inside the various legs. “Lively, not dark colors, to give identity to different spaces,” he said. “And then you come up into this world of concrete.”

The gallery level will include 26 so-called Core Galleries, Zumthor said, “each one with a particular color. The Pompeian red gallery, or the indigo gallery.”

Working with American engineers — and lawyers — occasionally tested Zumthor’s patience. Concerns about liability constrained his design, he said, robbing the LACMA building of some of his signature gestures. “Architecture used to have this craftsmanship, that you could see who made it.”

On an early concrete pour for a large section of wall, Zumthor said, the construction crew “made this big mistake” — caused by a water leak — and offered to repair the resulting damage “so you hardly see anything.” Zumthor, though disappointed, ultimately persuaded Govan to leave the flawed wall in place rather than patch or replace it. He added, “You don’t fix this. You cannot repair a sculpture.”

One of the costliest aspects of the new building is its unusually sophisticated seismic engineering. The building will feature 56 base isolators, which provide strong protection against earthquake damage; each weighs 40,000 pounds. In Los Angeles only a handful of buildings — including the new 16-story Wrapper tower on Jefferson Boulevard and the forthcoming Lucas Museum of Narrative Art — use the system.

The lead architect of the Wrapper and former director of the Southern California Institute of Architecture, Eric Owen Moss, said that in his view the most compelling element of the Geffen design is the portion spanning Wilshire. He called it “a kind of Ponte Vecchio piece,” referring to the medieval bridge across the Arno River in Florence: “The museum becomes an inhabited piece of infrastructure. I think that adds something to the lexicon in Los Angeles.”

Others have been less kind. The LA-based critic Mimi Zeiger, writing in a recent issue of The Architectural Review, called the Zumthor design “wrongheaded” and, given the energy demands of concrete construction, “environmentally tone-deaf.” Referring to the section spanning Wilshire, which some observers have compared to a segment of freeway, she wrote, “Overpass comparisons aren’t hyperbole.”

Wendy Gilmartin, a Los Angeles architect and writer, said in an email that in the Museum District, of which LACMA is a part, too much space and public subsidy had gone to “big, muscular design projects” such as the Geffen building while “opportunities for small cultural spaces are dwindling.”

Among the most pointed criticisms of the new LACMA wing is that it won’t create any additional exhibition space, on balance, for the museum. The LACMA website notes that in the Geffen Galleries “there will be approximately 110,000 square feet of gallery space, replacing approximately 120,000 square feet of gallery space.” Art critics in particular have faulted the reduction in exhibition space in a public institution.

“First of all,” Zumthor said, “people look at the plan and tend to think, the galleries, that’s the museum, and the rest is circulation. That’s completely wrong. They will see this when they go there, that this doesn’t account for all of these interstitial spaces.” Zumthor was referring to the wide circulation spaces along the perimeter of the building that will also contain art; the museum calls these Meander Galleries.

He added, “The real response is, ‘Hey guys, it’s not about size.’ Where does idea come from, ‘We can make an interesting museum by showing everything’?” He added, “It’s a huge museum. We will see. It might be too big for one person in one day, even though it’s on one floor.”

Govan was equally adamant on this point.

“Why is this even a question?” he asked. He said the gallery space inside the pair of buildings designed by Renzo Piano that opened on the LACMA campus after Govan’s arrival — the Broad Contemporary Museum in 2008, followed by the Lynda and Stewart Resnick Exhibition Pavilion two years later — should be part of this calculus. “We built the addition first, so we could operate the museum while we tore down” the older buildings, he said.

Govan said that making the new wing larger than the original museum campus would have triggered additional, and costly, parking requirements. The Zumthor building includes no parking spaces. An extension west along Wilshire of the Metropolitan Transportation Authority’s D line will add a subway stop steps from LACMA by 2025.

Zumthor, for his part, said that the vast urban scale of the LACMA project appeals to him and has clarified the kind of architecture he wants to pursue from now on: “It should be considerably big, and strong — the possibility to shape something.” He added, “I wouldn’t do small things, refined things. This is over.”

This echoed rule No. 3 on the list of 10: “Look for the big not for the small.”

He added that Govan had continually encouraged him to simplify the design. “Michael would tell me, ‘Be more American. Be more rough.’ ”

This is not surprising given the other museum and gallery projects that Govan has overseen. In developing the Dia Beacon complex in New York’s Hudson Valley and in refining final plans for the Resnick Pavilion, he has shown a preference for high-ceilinged spaces with straightforward detailing where the architecture, rather than imposing itself on visitors, tends to recede.

“I do have that matter-of-fact aesthetic, and interest, which is one of the reasons I like Peter — the honesty, and all that,” Govan said. “But mine is more pared back.”

I asked Zumthor near the end of our conversation if working in Los Angeles had been trickier than he’d anticipated. “This was a blank sheet for me at the beginning,” he said. “I had no idea what this process would be for me.”

This suggests he may have skirted rule No. 10: “Know all the requirements before you are designing.”

All in all, Zumthor said, the Los Angeles experience has been “worth the suffering.” He acknowledged that he is not always the easiest architect to work with, in part because he prefers to reserve the right to make design updates as a project evolves.

Govan didn’t disagree: “Peter feels that in Europe he is allowed to have a more iterative design process, and he can go back in and he can change things, and he can change things, and he can change things.”

“There’s trial and error,” Zumthor said. “At the beginning, I always say to the client, ‘This is my artistic process.’” Zumthor grabbed a pen and on a blank piece of paper drew an elaborately curving, twisting line. “‘So, do you still want to do something with me?’”

This article originally appeared in The New York Times.