Retrospective plans for a dormer window roof extension on Harbour Road in Beadnell may be refused by Northumberland County Council.
Officers are recommending that the north area planning committee refuse the application by owner Frank Holmes.
Planning officer Sarah Witherley, in a report to members, said: “By virtue of its scale, massing, height and overall design, this retrospective development appears incongruous upon the host property, wider street scene and AONB.
“As such it is considered inappropriate for its context and harmful to the appearance of the host property and the Northumberland Coast AONB.”
She said Mr Holmes had shown willingness to work with the planning authority but the restrospective application could not be supported.
The application site is a two-storey terraced house in a row of six similar properties.
The dormer measures 6.5m in width and is stepped in from either side. It extends up to the original ridge line but not beyond.
Beadnell Parish Council considers the extension to be intrusive, large and not in keeping with the area and would set a precedent.
The AONB officer added: “It would be disingenuous to grant permission for this box dormer, which is contrary to guidance, on the grounds of it being a retrospective application.”
Neighbour Russell Field, of Beach Court, also expressed concerns.
He said: “This extension covers the full width of the roof and thus is completely out of scale on what is a traditional terraced property.”