Useable Head Height vs Volume

[harry_angel]

Hi - looking at PD rules for loft conversion... 

 

The Govt doc - "Permitted development rights for householders - Technical Guidance" (https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/830643/190910_Tech_Guide_for_publishing.pdf )

- says you can convert your loft under PD unless "the cubic content of the resulting roof space would exceed the cubic content of the original roof space by more than - (i) 40 cubic metres in the case of a terrace house, or (ii) 50 cubic metres in any other case"

 

My question is: when calculating the volume of the possible roof space (to check if it falls under PD), should you include the measurements for the ENTIRE space, or would the Council really only be concerned with the USEABLE space i.e. any space that has a reasonable height? Ultimately, what counts?

 

(I think the minimum height for useable space is 150cm? According to Govt doc called Technical Housing Standards: Nationally Described Space Standard - "any area with a headroom of less than 1.5m is not counted within the Gross Internal Area unless used solely for storage")

 

Also, if you have a quick and easy way of doing this calculation, that would be great too! 

 

Thanks all - your assistance and wisdom, as always, is much appreciated. 

[Big Jimbo]

I think you need 2 calcs Harry. The first would be the volume of the total roof area. The second would be the dormer addition. It's the addition. It's the addition that needs to be less than 40 or 50 square mt. I think it's the outside measurement of the dormer that would count. Ie; 6m long/wide. 2m high. 4m deep. The sum would be 6x2x4divided by 2 if the dormer was being added to an existing sloped roof.

[harry_angel]

Hey @Big Jimbo, does that mean that the original loft area - that was unused previously but will now be converted - does not count towards the measurements the Council would look at if questioning the PD nature of the project?

 

Are you saying that it is only what is physically and materially added to the original roof that matters? 

 

Maybe I misunderstood this - I thought that all unused space that was then made 'habitable' was part of the conversion calcs (whether it was physically there previously or not) - because you are adding to the volumetric uplift of your house in a useable capacity.  So that is wrong? 

[Big Jimbo]

Harry the naughty. The middle One. "what is physically and materially added to the original roof"  whatever of the existing loft that becomes habitable space don't count because it already exists......So just what you are adding on in respect of volume buddy/

[harry_angel]

Belated cheers @Big Jimbo

 

Would have responded sooner, but was swamped with putting together the planning app in time....to avoid the enforcement notice....in order to waste as much time as possible.

 

Because apparently that is what I am reduced to: a pro council timewaster!