The A595 will be completely shut near Grizebeck this weekend.
The temporary measure will be put in place at Dove Ford so that work can be done to replace the roof of a dangerous farm building.
Cumbria County Council say the road will close for safety reasons in both directions from 8am on Saturday morning - it's likely to stay in place into Sunday.
A signed diversion will be in place via Grizebeck, Greenodd and Dalton.