BEVERLY HILLS, Ca. — It takes more than a cheesy reunion movie to get the six original Brady Bunch kids together these days. 

But when HGTV won a bidding war against Lance Bass to buy the nondescript North Hollywood house seen in the establishing shot in every episode of their iconic 1970s sitcom, the once young cast — now aged 57 to 64 — had good reason to reassemble for A Very Brady Renovation, premiering Sept. 9. 

"What resonated with me the most was that it was a different take on Brady," says Eve Plumb, the former Jan Brady, who hasn’t participated in every nostalgic reconvening. 

"They weren't asking us to come back and play Brady Bunch characters again. It was: Let's explore what the house would be like if we could make it in real life, and please help us do that. And I started watching all the HGTV shows, and I went, 'This is going to be good.' "

Working with the established renovation stars of the network, they saw the home change to include the familiar (and sometimes garish) decor of those days — adding 2,000 square feet to include it all.

"I’m a huge fan of HGTV and all the shows that they do," said Maureen McCormick, the once ever-positive Marcia. "I talked with the people, and I just felt like they had a love for this project, and I felt like this would be a really good one to be involved with."

The resulting renovation series is "the most expensive show they've ever done," says Barry Williams.

Williams, 64, who played the elder Greg Brady, made his comments standing amid a lavish HGTV party at the Beverly Hilton that followed their TV Critics Association summer press tour panel.

There, Williams had commented that HGTV  "paid like way too much — I mean way too much for this house," which was listed for $1.8 million before the bidding war.

Because the interiors (and backyard) of The Brady Bunch were shot at Paramount Studios in Hollywood, the young cast had no particular connection to the scene-setting San Fernando Valley mid-century modern home.

"We had no recollection of it," says McCormack. "I mean, it was placed as an establishing shot into the show."

"I didn't learn where this house was until 1996," says Christopher Knight, who played Peter.

Williams recalled he was once invited to the private home by mutual friends who awaited his reaction. 

"They assumed that I would recognize it walking into the house, I guess. And I didn't," he said. "They had to walk me back outside to look at the photograph that we see on television for me to make the connection because the inside resembled it not at all."

Owners had made various changes in the facade, but there was no way it could have fit the interiors seen in the show. 

"That picture window in the upper part of the house that's the iconic symbol of the house — that was dressing," said Mike Lookinland, 58, who played Bobby.

Even as the youngest Brady, the 57-year-old Susan Olsen says "I looked at that house and thought to myself, 'No way. That could never be the set. It's a one-story house.' "

Making it the two-story of the show was part of the construction challenges. The network says it shot more than 9,000 hours of the demolition, renovation, and careful replication of the house - which, with its floating staircase, proves to be as beloved a component of the old sitcom as its stars.

The transformation begins with a tour of the existing house, which looked little as the studio-created sets did. Then McCormack and Olsen join Property Brothers Jonathan and Drew Scott in working on the entryway, living room.

The brothers also work with Knight on the exterior; the orange and green kitchen is also a project for Knight with Plumb, working with Leanne and Steve Ford of the show Restored by the Fords.

Lookinland and Plumb join Good Bones stars Mina Starsiak Hawk and Karen E. Laine in working on the kids' bedrooms and the Jack-and-Jill bathroom. Williams works on dad's den with Jasmine Roth of Hidden Potential, and the two of them work with Lara Spencer of Flea Market Flip to makeover Greg Brady's groovy attic hideaway. "Yes, the beaded curtains are there," Williams says.

"They didn't just replicate," the former Greg says. "It is almost a perfect replication, from fabrics to carpeting to furniture to decorating to artwork to the fake grass in the backyard."  

"If something couldn't be found or sourced, they made it," Plumb says. "The printed fabric to match for the couch. They made a beautiful stereo cabinet that we put together and I helped to stain. We did crafting projects for artwork. I repurposed a couple of the paintings that were in the den and one over Jan's bed to put in the show, so all of us were involved in all aspects of it."

They even imagine a space seen only a couple of times in the series — the living quarters of Alice, the comic maid played by Ann B. Davis. 

"They studied every single frame that was available," says Plumb, who worked on the room with Spencer. "We shopped for the things that we could find for her dresser. We had a real hard time finding those lamps. We had to sort of recreate them."

One addition is that the maid's quarters now has a bathroom. 

"I think Alice scored the best upgrade," Lookinland says.

"One of the other things that's nice about recalling the experience is we are the surviving members of the cast and we can feel the presence of Robert Reed and Florence Henderson, Ann B. Davis, in these rooms that are being created through the memories and the shows,” Williams says. The actors who played the adults on the show have died in the intervening years. 

By showing old clips of the show in the renovation series, Williams says, "we can share their presence and what a significant part of our show they are and were. It's a nice way to keep them introduced."

Adds Lookinland, "They would've loved it."

A Very Brady Renovation culminates at the end of September at about the time of the 50th anniversary of the first broadcast of The Brady Bunch, Sept. 26, 1969.