Two roads in the centre of Llandudno have been closed amid fears a former hotel could be in danger of collapse.
Mostyn Broadway and part of Vaughan Street have been shut after engineers became concerned about the structural safety of the old Tudno Castle Hotel.
The hotel site is being redeveloped in a £10m scheme to include a new Premier Inn, shops and restaurants.
Developers said "historical movement" in a wall structure was found to be far more severe than had been assessed.
A spokesman for Bowmer & Kirkland said the company would do "everything it could" to reopen all roads before 28 April.
He added: "We felt that an immediate road closure was prudent to protect members of the public, should there be further instability and risk of collapse on to the road outside the site.
"Unfortunately, two thirds of the facade on Mostyn Broadway cannot be saved, so we will demolish the failing part of the structure and rebuild it."
Traffic diversions were set up after Conwy council issued an emergency closure notice.