How big is this extension

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Hi there,

I'd like to build an extension 4m deep by 5m wide on the back of my detached house. The house was built with the ground floor 2m deeper than the 1st floor so there is a 2m deep protusion across the whole of the back with a pitched roof covering it. I thought that I could run a roof over the extension with the pitch at 90 degrees to the existing roof and joined onto it by to form 2 valleys at 45 degrees. The ridge of the new roof would be 25 cm higher than the exiting roof as I would sit the ridge board on the ridge board of the existing roof.

The builder came round last night to discuss my thoughts and get the information that he needed for a quotation and we found a problem. I think that the extension will be a permitted development as it is 4m deep measured from the bottom of the original wall. He says that the extension is 6m deep as it should be measured from the original 1st floor because the new development actually starts from there. His view is he will only get involved if I get either prior approval for a 6m extension or get planning permission. He says that he made the mistake when he was younger of getting involved in PDs that turned out to be non-PD and doesn't want the hassle.

So, is it a 4m extension or a 6m extension. I spoke with the LPA this morning and got a definite maybe from the guy.

I have attached sketch (I hope)
 

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So is the bit that sticks out the back of the house already, an old extension or the original house?

If the house was built with that then your builder is wrong, and you do not need planning permission and it will be classed as permitted development.

If that part is an extension then your builder is correct and you will need to get planning permission
 
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Thanks for that. So I can apply for a LDC (suggested by the guy from the council to get a definite answer) with confidence and then re-engage with the builder? I had intended to get a LDC anyway but was thrown by the builder.
 
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Beg to differ here - I'd say that would be a 6m extension requiring either P.P or Prior Notification (a LDC wouldn't apply as at 6m it would not be Permitted Development).
 
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Beg to differ here - I'd say that would be a 6m extension requiring either P.P or Prior Notification (a LDC wouldn't apply as at 6m it would not be Permitted Development).

If it's the original house how does it turn into a 6 metre extension?
 
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If it's the original house how does it turn into a 6 metre extension?

The reasoning is that as part of the roof of the new work extends over the roof of the existing extension (and presumably touches the main rear wall of the house) it becomes a 6m extension, albeit that 2m of it is above the original roofline.
There are a number of appeal cases on the Planning Jungle website which confirm this view.
The OP's council might, though, take a different view?
 
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I can see why my builder backed off and why the guy at the LPA was less than committed. The builder suggested that I started a whole new roof on the extension, hipped on all sides with a valley between it and the original roof. I don't want to do this because it would look cr*p and l would have an inaccessible gutter between the two roofs. Any suggestions?
 
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@tony1851 I'm happy to search the Planning Jungle but do you have any links. Please don't go doing a search that I could do myself.
 
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No builder can give a meaningful quote without detailed design drawings and specification.
 
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@woody, the builder wanted a plan sketch and a side elevation. The thinking was that, since he is a builder and I'm not, we would develop the details to a point where he could give me a quote for labour and materials.
 
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The extent of any extension is measured off the original wall(s) and IMO you're planning on extending 6m off the original wall with the roof and thus would not be PD. You could try your hand at an LDC to see if it gets through or just go for PP which I suspect (depending on local planning policies) would be successful.
 
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The reasoning is that as part of the roof of the new work extends over the roof of the existing extension (and presumably touches the main rear wall of the house) it becomes a 6m extension,?

So if you left the original bit of roof in place and stopped the new roof at the 2m line with a small gable that would be OK?
 
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So 3 people, including the builder, think that it will be 6 m and 1thinks 4 m. I think I'll put in a request for prior approval and hope that there aren't any objections. The LPA has a presumption against extensions greater than 4 m so would reject it if there were. Plan B if I don't get PA is to put a separate roof on the extension. It won't look as good but it would be better than an extension that is effectively only 2 m deep.

Thanks for all your help.
 
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@woody, the builder wanted a plan sketch and a side elevation. The thinking was that, since he is a builder and I'm not, we would develop the details to a point where he could give me a quote for labour and materials.
But what specification is he quoting you for? High performance insulation, top grade windows, stainless fittings? Or bargain basement? What if building control want something that the builder has not but should have accounted for? Or your plan drawer draws up a different design and specification?

And when the next builder comes to quote from his little crib sheet, how are you going to compare quotes when the builders are not quoting on the same things?

Builders get their new cars off clients like this.
 

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