Lafayette Square, the north sidewalk of Pennsylvania Avenue and Jackson Place NW and Madison Place NW will remain open to pedestrians and cyclists.
The 6-foot-6-inch fence is being replaced by one approximately 13 feet tall, with wider and stronger posts, the Park Service said.
The Park Service and Secret Service began work on the new fence around the 18-acre White House complex in July. The work will be completed in eight phases using more than 3,500 feet of steel fencing.
The new fence incorporates anticlimb and intrusion-detection technology and is designed to mitigate security threats, the Park Service said.
Overall construction is expected to continue into 2021.
There have been numerous incidents in recent years where people have tried and sometimes succeeded in getting over the fence.
In June, a Pennsylvania man jumped the fence, saying that “voices in his head told him to,” according to court documents.
After his arrest he said he was “on a covert mission” to tell the president about “ ‘Project Armageddon’ and that the Mariana [sic] Trench was going to crack in 9-10 years,” the Secret Service reported.