The start of construction on the One West Main office building will close South Fir Street between West Main and West Eighth streets starting Wednesday.
The street will be closed continuously until further notice, city officials said.
Adroit Construction is building the office complex near the Evergreen parking structure. Sidewalk closures and on-street parking removal adjacent to construction will also be in effect.
Motorists in the area should seek alternate routes. For more information, contact Medford Public Works at 541-774-2100.