Behanllp Chartered Surveyors
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Preliminary Feasibility Assessment


Example of the BRE 209 paper’s initial assessment for daylight and sunlight, the 25° line assessment. In this instance the proposal shown in red falls within the 25° line from the neighbouring property and daylight and sunlight are unlikely to be a problem.


Example of the BRE 209 paper’s initial assessment showing that both neighbouring properties will be affected under the 25°asessment and therefore further analysis will be required.


Image showing the use of a contextual 3D model to illustrate whether a proposal fulfils the BRE 25°line assessment on two of the neighbouring properties


Image showing a rendered view of a contextual model and how in this case the extended roof area in red breaches the 25° line of three neighbouring properties.


Using sections or elevation drawings it is possible to look at the potential rights of light effect of a proposed development by projecting sight lines in a 2D fashion showing the existing versus proposed effect. In this example the differences are very minor.


RICS Guidance Note “Daylighting and Sunlighting”
Mark Behan is a member of the working group that produced this guidance note. This guidance note provides advice to surveyors who accept instructions to advise on daylight, sunlight and shadow calculations for developments. It explains the different types of assessment available, reporting procedures and the roles that the Chartered Surveyor will need to perform.