Knotel continues its rapid expansion in New York with two new leases that put it over a milestone.

On Monday, the on-demand headquartering firm announced that it had signed leases to occupy the ninth floor of the Fred F. French Building at 551 Fifth Ave. in Midtown Manhattan and the 14th floor of 123 William St. downtown. With those leases, Knotel has more than 500K SF in locations across the United States.

Knotel has built its portfolio rapidly but steadily, with leases around 20K SF across New York (and one in San Francisco). Its lease at 123 William is for 24K SF, and will run for 10 years once Knotel moves in by February. It is the second lease Knotel has signed with landlord AR Global Investments, after 200 West 41st St.

Knotel's Midtown lease also follows its M.O., giving it 21K SF in the landmark Fred F. French building, built in 1927 at the corner of Fifth Avenue and 45th Street and owned by an affiliate of The Feil Organization. Knotel signed a five-year sublease with a hospitality management company, it said in its announcement. Among the known tenants at 551 Fifth Ave. is Denihan Hospitality Group. Knotel will move into its space immediately.

Distinguishing itself from co-working competitors such as WeWork, Knotel designs and manages custom headquarters spaces for companies that have "outgrown co-working." WeWork has bucked against the perception of serving only smaller tenants by signing IBM and Amazon to deals to occupy full locations of over 100K SF.

Knotel has partnered with smaller co-working firms like Grind and, more recently, Galvanize to provide two-way referral services, with Grind and Galvanize sending larger potential members to Knotel and receiving recommendations for companies with space requirements that Knotel deems too small for its services. Knotel has also claimed that WeWork has attempted corporate espionage at multiple locations.