I too would be worried if I was you.
what sort of work is being carried out to the outside of the building and during which hours ?
the host absolutely shouldn't be arranging building work in a property while they have guests .
did the host offer a penalty free cancellation ? If you don't want to stay ask Airbnb to cancel penalty free because the host has just informed you they are now having building work for the duration of your stay.
before you do this do check availability for similar listings