An objection from your neighbour is not necessarily a reason to reject your application. Your neighbour would need to present solid and valid reasons as to why the proposed plans should not go ahead.
The following are the grounds on which planning permission is most likely to be refused (although this list is not intended to be definitive) :
• Adverse effect on the residential amenity of neighbours, by reason of (among other factors) noise, disturbance, overlooking, loss of privacy, overshadowing, etc. This does not include noise or disturbance arising from the actual execution of the works, which will not be taken into account, except possibly concerning conditions that may be imposed on the planning permission, dealing with hours and methods of working, etc. during the development.
• Unacceptably high density/over-development of the site, especially if it involves loss of garden land or the open aspect of the neighbourhood (so-called ‘garden grabbing’)
• Visual impact of the development
• Effect of the development on the character of the neighbourhood
• Design (including bulk and massing, detailing and materials, if these form part of the application)
• The proposed development is overbearing, out-of-scale or out of character in terms of its appearance compared with existing development in the vicinity
• The loss of existing views from neighbouring properties would adversely affect the residential amenity of neighbouring owners
• If in a Conservation Area, adverse effect of the development on the character and appearance of the Conservation Area
• If near a Listed Building, adverse effect of the development on the setting of the Listed Building.
• The development would adversely affect highway safety or the convenience of road users, but only if there is technical evidence to back up such a claim.