Permitted development - 50% rule

[Rich C]

Hi all,

 

I’m trying to understand the 50% rule for a single storey side extension which I was hoping might be permitted development as the government website is quite ambiguous.

 

I’ve a detached house built in the early 1970s, 8.4m wide with plenty of space around it. The original owners were put a small single storey extension on one side for a utility room in the 1970s approx 2.7 m wide (2.2m deep)

 

I’m now looking to put an extension on the other side of the house to use as a garage/workshop which I’d like to be 3.6m wide

 

Can the 50% of the original build rule be applied to each side separately? ie 3.6m < 4.2m off I go…

 

Or, as I expect, it’s the total of all side extensions and therefore in this case I’d need to get planning? Ie (2.7m+3.6m) > 4.2m

 

TIA

 

[RichardL]

I didn't check the rules again -  I have it in my head you can build on 50% of the plot let after the original build (+ some constraints for PD re only 4m out from the primary elevation)

(Plot - original house area) / 2 = space available

The extending from the house thing is a separate constraint - theres a brochure somewhere on the govt. planning site that goes into detail with examples.

Does that sound right?

[DevilDamo]

The actual PD term of 50% relates to the amount of land around the original house should not be covered by extensions, additions, etc…

 

It appears you’re referring to single storey side extensions should be no greater than half the width of the original house. So if your original/as-built house has a width of 8.4m, then you can add single storey side extensions to each side of max. 4.2m wide. There are of course other PD requirements to adhere to. 

[Temp]

There are two 50% rules. One involving the area of garden built on and the other involving the width of the house when side extensions are added. Regarding the latter..

 

The guidance says..

 

Quote

 

Where an extension is beyond any side wall, the restrictions in (j) will apply.   Any extension can only be a single storey, must be less than 4 metres in height and can  not be more than half the width of the original house.

 

The width of the original house should be calculated at its widest point. Under paragraph (ja) (see page 28) if the proposed extension is being joined to a previous enlargement, it will not be permitted development if the size of the total enlargement (being the proposed enlargement together with any previous enlargement) exceeds these limitations. For example, if a proposed extension of 3 metres in height is added to an existing extension which exceeds 4 metres in height, or if the proposed extension creates a total enlargement which has a width greater than half the width of the original dwellinghouse, it would not be permitted development.  

 

 

I believe two side extensions can effectively double the width of the house if  NOT joined to any other existing extension.  

 

If you already have a rear extension then adding a side extension can need planning permission if they touch that see pages 26 and 27..

 

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/830643/190910_Tech_Guide_for_publishing.pdf