Do I Need Planning Permission.co.uk
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Hi All,

I'm planning a single storey rear extension on my 1930s terraced house - 4.5m deep, full width of the house - 6m.

The house is on naturally sloping land, higher at the front. At the back of the house, there is a 0.7m drop to the patio and then a 0.4m drop to the original ground level (at the point of where the back of the extension will be).

The extension comes under permitted development if the height of the roof does not exceed 4m, measured from the "original ground level".

Does anyone know where the original ground level is measured from? Is it the original ground level at the back of the original house? At the back of the planned extension? At the front of the house? From the patio level?

I'm planning on a flat roof and keen to ensure that I stay within permitted development.

Thanks,
Ollie.

I have already answered on DIYnot (DevilDamo).

Damian, Your reply is impossible (for me) to find. Pre-1915 the answer used to be at the wall of the existing house. It now seems to be at the position of maximum height of the extension, ie in the case of Ollie, from the LOWEST ground level wherever that may be on the extension. because the clause referring to at the existing house is now omitted.

Pre 1915? The GPDO came to fruition in 1948, so not sure where you got that year from.

And what is it exactly you’re asking?