rate swaps as of December 31, 2018, and all trades were highly effective. The amended presentation and disclosure guidance which is required to be presented prospectively is provided in Note 4 to the consolidated financial statements included under Part I, Item 1 of this Quarterly Report on Form 10-Q.
Trends and Uncertainties
Economic Conditions
The economy in the United States is continuing to experience a period of economic growth, which directly affects the demand for office space, our primary income producing asset. The broad economic market conditions in the United States are affected by numerous factors, including but not limited to, inflation and employment levels, energy prices, the pace of economic growth and/or recessionary concerns, uncertainty about government fiscal, monetary, trade and tax policies, changes in currency exchange rates, geopolitical events, the regulatory environment, the availability of credit and interest rates. Any increase in interest rates could result in increased borrowing costs to us. However, we could also benefit from any further improved economic fundamentals and increasing levels of employment. We believe that the economy is improving in many markets and appears to be in a broad-based upswing. However, future economic factors may negatively affect real estate values, occupancy levels and property income.
Real Estate Operations
Leasing
As of June 30, 2019, our real estate portfolio was comprised of 32 operating properties, which we refer to as our operating properties, and 3 redevelopment properties that are in the process of being redeveloped, or are completed but not yet stabilized, which we refer to as our redevelopment properties. We collectively refer to our operating and our redevelopment properties as our owned portfolio. Our 32 operating properties were approximately 88.1% leased as of June 30, 2019, a decrease from 89.0% as of December 31, 2018. The 0.9% decrease in leased space was a result of the impact of lease expirations and terminations, which exceeded new leasing completed during the six months ended June 30, 2019. As of June 30, 2019, we had approximately 1,133,000 square feet of vacancy in our operating properties compared to approximately 1,046,000 square feet of vacancy at December 31, 2018. During the six months ended June 30, 2019, we leased approximately 835,000 square feet of office space, of which approximately 617,000 square feet were with existing tenants, at a weighted average term of 7.6 years. On average, tenant improvements for such leases were $26.69 per square foot, lease commissions were $11.18 per square foot and rent concessions were approximately three months of free rent. Average GAAP base rents under such leases were $31.46 per square foot, or 13.6% higher than average rents in the respective properties as applicable compared to the year ended December 31, 2018.
As of June 30, 2019, our three redevelopment properties included an approximately 130,000 square foot redevelopment property known as 801 Marquette in Minneapolis, Minnesota, an approximately 213,000 square foot property known as Blue Lagoon in Miami, Florida and an approximately 62,000 square foot property known as Forest Park in Charlotte, North Carolina. Given the length of the redevelopment and lease-up process, these properties are not placed in service until, in some cases, years after we commence the project.
The redevelopment at 801 Marquette was substantially completed at the end of the second quarter of 2017 and is in the process of being leased up; however, it is not stabilized. As of June 30, 2019, we had leases signed and tenant’s occupying approximately 37.0% of the rentable square feet of the property. We expect to incur redevelopment and lease-up costs of $27.7 million, of which we had incurred approximately $22.0 million as of June 30, 2019.
The redevelopment of Blue Lagoon commenced in December 2018 following the maturity of a lease with a tenant that occupied 100% of the property. We expect to incur restoration, redevelopment and lease-up costs of $28.1 million, which include work on the roof of the building, costs to make the space suitable for multiple tenants and to increase parking at the property. As of June 30, 2019, we had incurred approximately $3.7 million in total redevelopment costs. We anticipate completing the redevelopment by the end of 2019.
The redevelopment of Forest Park commenced in January 2019 following the maturity of a lease with a tenant that occupied 100% of the property through December 31, 2018. We expect to incur redevelopment and lease-up costs of $3.8 million,