Changing flat roofed extension to pitched for loft space (bungalow)

13 Oct 2023
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United Kingdom

We are in the process of buying a detached corner plot bungalow which has a fairly substantial flat roofed extension which was constructed under permitted development. I would like to do a loft conversion involving a hip to gable over the current flat roof of the extension. This would (I think) provide space for a large bedroom with en-suite and small bedroom/office.

Is it still considered PD to change the structure of the flat roof to pitched and does this impact on the 50m3 rule? The current roof is hipped over approximately 8x8m and extending this over the extension we're looking at a hip-gable of 8x12m. Would the 50m3 additional volume be taken from the original bungalow footprint or is changing a flat to pitched roof OK but the additional volume created by the gable end (or alternatively a dormer) is what counts for the additional volume?

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I don't know about the volume, hopefully someone else can advise. But if you're looking at increasing the peak height beyond its current peak then you will definitely need planning permission, and this can be difficult to achieve.

But if it improves the overall appearance then this will definitely help. It's not a certainty either way, all down to the case and the whims of those deciding.
Thanks Ivor, the way the roof is currently orientated I think it would be a case of extending the current ridge line, so maintaining the existing height. See the picture, Thick lines are the current roof, both hipped and flat, with the thinner line extending the ridge to a gable end overlooking the garden. As it's a corner plot the 'rear' extension is on what would usually be considered the side elevation.


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    Roof proposal.png
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That's not a loft conversion, it's a first floor extension. You'll need to review the PD criteria for that. Nothing to do with roof volume.
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Thanks Woody, I presume that is still the case if it was a dormer at the back rather than a hip to gable?

As I understand it those plans would need planning permission then as the existing flat roofed extension is 4m and max for a 2-storey PD is 3m. Would that also be the case if the gable stopped at 3m and then there was a flat roof below (I had considered that option to allow roof lights over the kitchen/living room)?

Any reason for planning to frown on the original plan? I think replacing the flat roof with a pitched one would look better, but you would be able to see the gable from the front...
Depending on what's around that single storey, and impact on the neighbours, there would normally be no good reason to reject an application for a well designed loft extension as you propose.

A rear dormer would be PD if it conformed to the criteria - mainly eaves set-back, roof lower than ridge, materials to match.
Thanks, I've had a chat to a local architect who didn't think it would be an issue (but hadn't noticed the 3m problem) and being on the corner there is only one neighbour who's bungalow has a hipped roof finishing roughly in line with the extension so don't see it impacting them really.

Just to clarify, you mean extending the hipped roof over the current extension and adding a dormer, which would give almost as much space as the hip to gable (but not look as good), would be PD?

A dormer in the back of the existing main roof and hip to gable conversion would be PD.

Extending the main roof over the flat roof requires permission.

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