A design flaw on the new World Trade Center could add millions to the construction cost of the new Freedom Tower, making it the most expensive building in the world, reports the Wall Street Journal

The new estimate for the building brings the total cost of construction up to $3.8 billion, $700 million more than the last estimate in 2008.

In comparison, the cost of construction for the Twin Towers was an estimated $1.5 billion, with each tower reaching 110 stories tall. 

The reason for the recent increase, according to the Journal, is that the loading dock under One World Trade Center will not be complete by the time tenants have to move in. Instead, the construction company will have to build a temporary loading dock on the outside of the building until the permanent one is finished.

The Journal also attributes the high cost of the building to security measures, construction cost overruns, and a decision by the Port Authority to now include leasing expenses in its public numbers.

However, those associated with the project predict rent from tenants of the building will help offset the cost of the project. Already, publishing company Conde Nast has leased out half of the building.

Patrick Foye, executive director of the Port Authority, said they still expect to finish the building by the end of 2013.