Lawful development certificate

1 Jun 2015
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United Kingdom
If I apply for a single LDC to build a loft conversion, a side extension and a rear extension under permitted development and the LPA decide that the side extension is not permitted development does the whole application get rejected or does the LPA grant the LDC for the loft conversion and rear extension only. I've contacted the LPA and they do not seem to sure.
I realise that an LDC is not really required if the proposals are PD.
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An LDC includes an assessment against the PD rules as "pass" or "fail". If something isn't PD it will "fail" and you won't get an LDC. If you want separate parts to be reviewed as separate applications they should be submitted separately.

You you do submit as one, you can try and negotiate with the LPA before they issue the formal notice. If they deem it is going to fail then you could ask them to give you an opportunity to amend the application / omit part of the works. Whether they let you do this will depend on the extent of the change required. There is not rule on this.

An LDC application isn't really be a test of what is PD, but confirmation that something is. If you don't think it's PD its a waste of time submitting it. The rules are relatively clear.
Attached is a drawing of what I am proposing. The second and third elevations detail the proposed rear dormer in grey.

The dormer will be clad with clay tiles to match as closely as possible the colour of the main roof grey double roman tiles.

The fourth elevation shows in concept the rear dormer with a rear ground floor extension that has a pitched roof. I believe that if the rear ground floor extension roof abuts the dormer then its volume counts toward the total permitted roof enlargement of the main roof under PD. The rear extension roof is pitched so that its volume along with that of the dormer works out to be about 49.5m3. The side walls of the rear extension are to be flush with the existing side walls of the bungalow. The flat roof is drawn without a fall as I'm not sure what fall I should put on it but what ever it is it will reduce the overall dormer volume albeit only slightly. Any suggestions as to the fall for the dormer roof?

The roof overhang of dormer does not quite extend beyond the existing rear wall of the bungalow but it is very close. The intention is to remove the existing rear wall of the bungalow once the rear extension is built, which is partly why the rear wall for the dormer is where it is i.e. so that it can sit on the steel fitted in place of the removed rear wall.

The bungalow is on a corner plot with its front and south facing elevations facing the highway. The rear of the bungalow faces the garden of the property behind which is approx 5m away at its closest point.

What are your thoughts firstly regarding the dormer proposal being PD and secondly whether I should include the rear extension on the same LDC application. The main reason for wanting to combine both proposals on one application is the time it will take to make 2 applications assuming they have to be done one after the other. Thinking about this------ can I submit 2 applications for separate LDC's at the same time?


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Have a look through a few applications on you local BC planning site. In my borough they can treat 2 parts separately even if in the same application. e.g. my own LDC:

Proposal Certificate of lawfulness for a proposed development to establish whether a two storey rear extension and a front porch following the demolition of existing single storey rear extension would constitute permitted development
Status Decided
Decision Part Approved, Part Refused​

The Porch was approved as PD, the 2-storey rear was refused.
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If they connect the whole thing needs to work to all applicable PD paragraphs (Class A, para. ja) and you cant pick and chose which rules to apply to which parts. That only works if they are distinct unconnected separate extensions so they are assessed separately. At present it will not pass as they connect:

It can't be classed as a single storey as it touches the dormer therefore the whole extension fails the single storey rules on height etc. If classed as a two storey it would then be two wide, etc. Basically the "single storey" is not a single storey and it fails Class A works.

You can only connect the single storey extension to a roof when the original roof is maintained and the roofpitch to the extension also matches or is similar to the original roof. As it connects to the dormer it's treated instead as one large extension so it doesn't work.

As the dormer/single storey extension wraps over the eaves I think it would also fail Class B works B2,b,i,bb. I think the only exception to this is when the roof extension is above original parts with different heights.

You cannot do the PDs separate and pass them both separate and then build both either concurrently or sequentially either... as once built it would fail. Nor can you do one part PD and one part planning then build them both, as the PD part would fail if built. You have to build the PD part (dormer) first then do the planning app for the single storey.


If you put a flat roof on the rear to maintain the extensions separate and to maintain the eaves it should be okay under PD. You can then build it all in one go and then apply for planning to change the roof to the single storey part if you so desire once built.

If you put a flat roof on the rear to maintain the extensions separate and to maintain the eaves it should be okay under PD. You can then build it all in one go and then apply for planning to change the roof to the single storey part if you so dyesire once built.

I was trying to avoid a flat roof but if I can't then I can't. One issue with a flat roof is that in order to maintain floor levels and ceiling heights of the extension to that of the existing building, the finished height of the flat roof may have to be higher than the bottom edge of the dormer due to the ground floor FFL being approx 150mm above DPC. This would result in the extension flat roof of more than approx 150/170mm in depth abutting the lower outer face of the dormer rear wall and, in which case, would I not be back in the same position as with the pitched roof?

Perhaps one way round this would be to move the dormer rear wall so it sits over the inner leaf of the existing rear wall of the bungalow, this would then give me approx 250mm for the extension roof depth?

What depth of flat roof should I plan for?
You could probably get the flat roof build up at about 250 ceiling to top finish. Less if you are will to use expensive insulation, or a hybrbid buildup.

You may be better simply to go for planning on it after building the dormer if height is a real issue.
I've redone part of my drawing (bottom elevation only) to show a flat roof extension with the dormer set back over the inner leaf of the existing bungalow rear wall. The extension roof is drawn at 200mm depth which decouples the extension roof and dormer wall by about 50mm.

However, the flat roof will still abut the main roof by 200mm. Would this mean that the volume of the extension flat roof would still be part of the permitted enlargement of the main roof (part of the 50m3)? If so, the volume of the dormer is now a little under 40m3 with the extension flat roof volume being a little under 5m3.

I've added roof lights to the extension flat roof due to reduced daylight caused by the neighbours 10ft + hedge out the back but these are not a must have.

Does this arrangement seem better and more likely to fall within the PD criteria and as such likely to pass an LDC application?

Unfortunately time is against us on this project so building the dormer first then applying for planning will make things very difficult plus if I get the rear extension shell built (with roof to come later) before the dormer goes in, hopefully the builder will be able to make sure the dormer wall and extension flat roof don't meet. Doing it this way hopefully will mean there won't any scaffolding access problems either for the dormer construction.

The amended part of the drawing shows dimensions in feet 'cos my friend the bungalows owner doesn't do metric!!!!!!


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It still won't comply.

Broadly a roof extension has to be above the original roof, and a rear extension has to be below the roof, and they cannot touch. You cannot have a hybrid as you cannot extend a roof extension backwards beyond the wall below.

The top surface of the flat roof to the rear extension has to be below the "eaves". (For a pitched roof the "eaves" is considered to be the lowest point on the roof where the wall would meet the roof pitch if no overhang existed). At the moment it is still shown higher. I've sketched the limit of what would be allowed. (refer Class A,A.1,d - pages 11-12 PD technical guidance)

Of course lowering the extension would then mean the dormer wouldn't meet even if it then sat above the wall below. However, there is another rule requiring 20cm of eaves to exist below the dormer. (refer Class B,B.2,b,i,bb - pages 36-37 PD technical guidance). There is some case law on this point which the technical guidance explains as: "This 0.2m set back will be required unless it can be demonstrated that this is not possible due to practical or structural considerations." I however have not seen any examples where someone has done this with an LDC for a dormer and rear extension (although people have built them but whether they comply or not is a different matter). The main case law example that permits breaking this rule is when extending over an original house and outrigger which different roof heights (and thus wrapping over the eaves where the eaves on the taller part continue over the lower part of the original house). So whether you maintain 20cm or not will be a judgement call and perhaps discussion with your Local Authority.


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I've re-redone my drawing and removed the rear extension altogether as the important part for now is really the dormer. Do you think the attached drawing will be OK for an LDC application (note the notes which I will change to black before submitting)?
See drawing: ElevationsPD004b.pdf

There are a couple of other issues which I need to sort out before making the LDC application:

  • The existing bathroom and the new one are at the rear. The existing soil vent pipe is externally fixed to the rear wall as per the thick red line on the drawing showing the rear elevation. Reading through the PD regs it would appear that I can alter the soil pipe by simply extending it upwards and terminating it at no more than 1 metre above the dormer roof height, is that correct and should I include this alteration in my LDC application? For now simply extending it up would be easiest and if the rear extension goes ahead then it will be moved altogether.
  • The existing boiler is located in the centre of the building and very slightly to the rear of the ridge line with its flue protruding through the rear roof slope. Can the flue be moved under PD to the front slope (obviously done by a Gas Safe engineer)? If so do I need to include this alteration in my LDC application? For now simply moving it to the front roof slope would be easiest and if the rear extension goes ahead, then the boiler and it will be moved altogether. See front elevation
For the purpose of understanding the PD criteria for roof height, existing eaves, overall height, volume, connecting roofs etc correctly, I've also redrawn the side elevation showing the rear extension. Is this proposal likely to meet the PD criteria?

The eaves gap between the face of the dormer and the top of the extension roof is about 230mm, which I realise doesn't leave much for measurement and drawing error and in practice may end up being less. If I maintain floor and ceiling heights throughout there is about 120mm for the ceiling and roof depth. Are there insulation materials available that would suit such a shallow roof depth?

See drawing: Southside with rear extn.pdf

I won't be submitting anything for the rear extension at this time but I may do later.


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  • Southside with rear extn.pdf
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