As he looked up at the ceiling inside First Avenue nightclub for about the 5,000th time in three weeks on Thursday, general manager Nate Kranz sounded extra confident about the remaining work needed to get Minneapolis’ landmark rock venue up and rocking again by Friday night.

“Sound and lights are mainly it — and that’s more our area of expertise,” Kranz said. “Although, we do know a whole lot more about plaster lath than we did three weeks ago.”

No, plaster lath is not the name of the latest Brooklyn buzz band. It’s what fell from the ceiling on Aug. 12.

About 30 minutes into a concert by Canadian metal group Theory of a Deadman, a 30-foot section of the ceiling dropped onto the back portion of the dance floor, forcing an evacuation and sending three fans to the hospital with noncritical injuries.

Sixteen days later, the club’s famously curved doorway is scheduled to open to the public again. Barring any last-minute hang-ups, the venue will reopen Friday at 8 p.m. for a concert by hometown hip-hop crew Grrrl Prty. And you better believe it’s going to be a party.

“I was secretly hoping Grrrl Prty was going to be the first show — what better way to kick it off?” joked the group’s DJ, Shannon Blowtorch. More seriously, she said the band was greatly worried about the club. “I would hate to see anything happen to my favorite venue that I call home.”

Many fans also voiced their concerns for the club on Tuesday night at the State Theatre, where ’80s alt-rock bands the Church and Psychedelic Furs performed. It was one of the club’s two big concerts that had to be moved to another venue during the shutdown.

“The State is fine, but I really don’t want to see concerts anywhere else than First Ave,” said Guy Hamernik, who drives up from Rochester.

Even the Psychedelic Furs’ Richard Butler spoke up: “We were happy to be booked at First Avenue again,” he said on stage. “We love that place.”

No more jokes about tearing the roof off the place, though, the staff requests. The roof was actually rebuilt in the early-’00s and is in fine shape. It had nothing to do with the fallen ceiling section. In fact, the solidity of the roof is more apparent now that the ceiling repairs are done. Crews did not replace the old lath and plaster. They tore it out, exposing the metal trusses that were hidden behind. The ceiling is now about 3 feet higher.

“We really didn’t know what it was going to look like without [the lath], and we were pleasantly surprised,” said club co-owner Dayna Frank.

Of greater concern was how the changes would affect the sound, staff said.

“I think it might actually sound better,” said Greg Huber, a sound engineer overseeing the work Thursday. “If anything, it will just break up and soften the sound a little.”

From 1936 to 2015

The lath and plaster that fell was believed to date to 1936. That’s when construction peaked on the Greyhound bus depot, which would open a year later, then become a rock club 34 years later (1970) and live on for 45 more years to become one of the most longevous and widely respected venues in the world.

This month’s closure was one of only three extended shutdowns remembered from the club’s run. The longest was just one day longer, when a 2004 ownership battle resulted in original owner Allan Fingerhut filing bankruptcy on the club and forcing a 17-day shuttering. The other was a 10-day shutdown in 1983 to film the live performance scenes in Prince’s movie “Purple Rain” — the event that put the club on the map internationally.

That reputation was reinforced after the ceiling collapse, as national TV networks and international media reported on the incident.

Closer to home, rock vet Curtiss A — who hosts the club’s John Lennon tributes every Dec. 8 — left a voice mail for Kranz the morning after the accident offering to head up a benefit concert or just help clean. Turns out, the arduous cleaning that came after the teardown might have been one upside of the collapse. “Honestly, I don’t think this place has ever been cleaner,” Kranz said. Pointing to inspections done in the aftermath, he added, “It’s the safest this club has ever been, too.”

Frank emphasized the concern for the three injured patrons throughout the three-week ordeal. Two were released from the hospital that night, while a woman stayed for about two days. “They’ve very much been in our thoughts this whole time,” she said.

Frank’s dad, Byron Frank, took away another positive. The club’s longtime accountant, Byron took over First Ave in 2004 after the bankruptcy court battle. He has since turned down offers from concert companies such as Live Nation to sell, instead handing the reins to his daughter, Kranz and their team in 2009.

Admiring the progress on the club’s renovations Thursday, the elder Frank looked down at the staff in the room instead of up at the ceiling to give his assessment on the shape of First Ave.

“After the way they handled this and got this place back in business,” he said, “I’m 100 percent confident that First Avenue is in good hands and should be here for the next 40 to 50 years.”