HOUSTON-After an 18-month market evaluation and negotiation period, Cornerstone Mortgage Company has signed a long-term renewal and expansion lease for 49,574 square feet at 1177 West Loop South. The company has been a tenant in the class A building for 12 years and uses the space for its corporate headquarters.

Cornerstone Mortgage’s lease at the 341,947-square-foot building was set to expire in December 2011. The company initially considered purchasing its own property, but decided to against it because the cost was prohibitive and concerns about lack of flexibility, according to Marshall Clinkscales of Colliers International’s local office.

Clinkscales represented the mortgage company in lease negotiations. The landlord, Houston-based Griffin Partners, was represented internally by Chris Lewis.