Rear Dormer "additional Roof Space"

[lizpearce82]

Hi

We are looking at doing a loft conversion but need a dormer on the back for the height of the bedroom & bathroom we are adding.
The roof is currently a pitched roof - only used for storage.
We are looking for clarification of what "additional roof space" actually means in Class B. Is it;
1. the extra space we are adding, on top of the volume in the pitch already - i.e. the cubic capacity of the added dormer only; or
2. the extra space we are adding to the house - i.e. the cubic capicity of the existing pitch (which is not currently habitable) and the dormer?

Sorry of this has been answered in other threads, I just cannot find a definative answer anywhere!
Many thanks in advance

 

[tony1851]

It is your point 1 - additional roof volume.

 

[lizpearce82]

Tony1851

Many thanks - that's how I read it, but cubic capacity of 50m3 or less must cover most dormer extensions so we just wanted to check.

Thanks again

 

[clifford1]

Unless of course you mean an inverted dormer, which would reduce roof space

 

[DevilDamo]

but cubic capacity of 50m3 or less must cover most dormer extensions so we just wanted to check.

It probably does for most semi-detached and some detached buildings but not when you're talking about larger detached houses. I've done a lot of roof extensions (i.e. hip to gable and rear dormers) that have come under the 40 cu.m threshold for terraced houses.