Jay Z and Beyonce
Beyoncé checked out a $21.5 million penthouse in Chelsea last month without Jay Z.Reuters

Beyoncé allegedly checked out an apartment in New York without husband Jay Z, adding to rumours of a marriage breakdown.

According to the New York Post, the Halo singer secretly viewed a $21.5 million Chelsea penthouse in Manhattan last month.

"She was very quiet, as if she was looking on the sly," an insider told the publication.

According to the source, the 44-year-old rapper has always played a strong role in the couple's real-estate deals and his absence raised eyebrows.

The couple currently reside in a 8,309-square-foot mansion in Tribeca, with their two-year-old daughter Blue Ivy.

"I can say with certainty that Jay is not downsizing," the insider added.

"There's no way a $20 million apartment is for her mother or her sister. That would be wildly unlikely,'' the source said.

Rumours that the two are having issues in their marriage started in May, when a video of Beyonce's sister Solange Knowles physically attacking Jay Z emerged, after the Met Gala. Jay Z's closeness with designer Rachel Roy allegedly provoked his sister-in-law, Solange, to fly into a rage.

Following that, Beyoncé and Jay Z were noticeably absent from Kim Kardashian and Kanye West's wedding in Florence, Italy on 24 May as well.

It was previously reported that the music power couple, who are currently on their joint On The Run world tour, are not on talking terms.

However, amid reports that their relationship is on the rocks, Beyoncé posted a message on Instagram, indicating that all is well between the two.