Kyle Richards is finally confirming at least one swirling rumor ... revealing she and Mauricio Umansky are no longer under the same roof, and opening up about her first day solo at her L.A. pad a solid 9 months after their split.

The "RHOBH" star spilled the tea on the "Bitch Bible" podcast -- she says Mauricio left their home of 28 years, and moved into a swanky West Hollywood pad, while she was away for a weekend -- leaving her to face the sudden, eerie silence of their once bustling abode.

As a mom to 4 daughters – Farrah, Alexia, Sophia, and Portia – and several dogs, Kyle admitted she's accustomed to a full house brimming with chaos. So, Mauricio's sudden absence made the whole situation totally weird.

Kyle choked up as she reflected, "I always knew when that day came it would feel strange, very real all of a sudden."

Also, just as Mauricio was settling into his new bachelor pad, their daughter Alexia spread her wings and moved out on her own after a few years of nesting at home -- which didn't help to soothe Kyle's emotions.

Despite the emotional whirlwind, Kyle confessed she saw Mauricio's move while she was away as a smart decision, on his part ... admitting she didn't want to be there to witness it unfold right before her eyes.

Nonetheless, KR says she's turning her marriage breakdown into a chapter of accomplishment, not failure -- especially with the awesome family they've raised together.