North Lincolnshire Council has refused plans put forward to build a new dwelling, including access and parking arrangement changes, at 3 Eastfield Road, Brigg, DN20 8DP.
An assessment report prepared by council staff said the proposal sought to sub-divide the "amenity area" of No 3 along the side of the existing dwelling to erect a separate single-storey detached property.
Council planners received three letters from the public expressing "concerns" about the application.
Outlining its reasons for refusal, the local planning authority said: "The layout, siting and design of the dwelling are not appropriate as the proposal would harm the setting and the street scene.
"The dwelling proposed would be out of keeping with the character of the area and would have an unacceptable impact on the amenity of the neighbouring properties."
Eastfield Road, a residential area, connects with Wrawby Road (the A18).
Anyone refused planning permission by a local authority may, if they wish, lodge an appeal to be carried out by an appointed inspector.
Meanwhile, planning permission is being sought to erect a detached bungalow on land at Kerrow Moar, Lidgett Close, Scawby, DN20 9AW (decision yet to be made by North Lincolnshire Council).
A decision is also awaited from West Lindsey District Council on a detailed application to erect one dwelling with garage on land off Smithy Lane, Bigby (outline approval having been granted in June 2021).