We're doing a rear extension and a loft conversion. In the process we're going to externally insulate and then render.

It's a mid-terrace house and the existing materials are brickwork and pebble dash, although our place is purely pebble dash.

Under condition A.3 (a) of permitted development it says
"the materials used in any exterior work (other than materials used in the construction of a conservatory) shall be of a similar appearance to those used in the construction of the exterior of the existing dwelling house"

Strictly speaking this kind of says to me it's not permitted development... although it could perhaps be argued that pebble dash and render are similar, particularly from a distance. Except, I guess, that I'm proposing our render to be off-white (as opposed to golden/brown colour it is now). In any case it's certainly not a listed building and there are examples around the neighbourhood where render has been introduced.

There's also the matter of the front wall getting pushed out 170 mm towards the highway by the insulation. Don't know where that fits into things. It will still be within the depth of the existing eaves.

http://www.planningportal.gov.uk/uploads/100806_PDforhouseholders_TechnicalGuidance.pdf

This has always been a point of great discussion. As you say, strictly speaking, the materials would not match. But most planners would take the view that rendering a brick or pebbledash house would be permitted development, others would say that it is only PD if some of the existing building is rendered (so you have an "appearance to be similar to") The "materials used in the construction" would be the same as they are not changing, they are just being EWI'd. Also there is the argument that if you painted it first, then rendering it afterwards would look quite similar.

Others would take the view that rendering (or indeed pebbledashing) is PD on a house if it is not in a conservation area, by the suggestion that it is only restricted at A.2 (a) for houses in conservation areas [Article 1(5) Land]

i.e. it is not PD on article 1(5) Land, so it must be PD elsewhere.

Then comes the issue of the projection of the EWI
The PD regs don't seem to have taken into account EWI which suggests that it is still quite unusual.
If you EWI the front of your house at the depth you are talking about (170mm) then in theory it is an extension forward of the principal elevation which is not PD (nor on the side if 2 storey house). This is obviously more noticeable on a semi or a terrace, but not such a big deal on a detached property.

PD regs have along way to catch up with what is required to deal with the existing housing stock, possibly in a nod to keeping neighbour relations amicable or being unable to let go of the "brick standard" as the appearance of a "house". What if you want to EWI and clad with timber? or something else? is it PD then?

If in doubt ask the LPA (if you are lucky and they haven't started charging for pre-application enquiries) and if necessary submit a planning application for £150 before they hike the price up. I am sure it will be approved.
If it isn't contact me privately.

Posted By: jamesingramone was unsure where to find an answer

That's because there isn't one.
Just 'opinion' or 'interpretation'
which is where it gets subjective!

I would have thought that covering pebbledash should be compulsory, and come out of council taxes (I live in a pebbledashed house).

What about building regs part L1b ? They say that when you re render you must insulate too!

Posted By: ShevekOne problem is that if you're within 2 m of the boundary then the whole of an extension cannot exceed 3 m in height.

I got this wrong. I've re-read it and it says "the maximum height of the eaves that is allowed for all parts of the proposal is three metres", not "the whole of the extension".

Posted By: Shevek"the edge of the enlargement closest to the eaves of the original roof shall, so far as practicable, be not less than 20 centimetres from the eaves of the original roof."

This one doesn't usually cause any problems. There are many cases where it is accepted as not practicable to comply with this bit. It really applies to dormers (Class B) and it excludes hip-to-gable enlargements (which this sounds a bit like?)

An obvious case where it would not be practicable is where you want to continue up with a masonary wall as leaving a 20cm gap would not make sense structurally.

If you want me to have a look I will give you an opinion on whether it is PD (if you have some plans).

About a year ago the government issued guidelines that EWI should generally be permitted development. It wasn't law, and it seems to be down to each council whether it follows the guidelines.

Unless you want to do the whole thing under the radar, I think you need to ask your council. Either just phone up the planning department informally, or go for a pre-application meeting. Ask what their policy is, and how they are handling the government guidelines, and whether anything apart from the insulation itself might be an issue - e.g. no longer having pebbledash.

If they can't give you a straight answer, a Certificate of Lawful Development might be the next step. Even if you are confident there will be no comeback, some people still like to have a COLD - or full PP of course - to wave at the buyer's solicitors when the house is eventually sold.

I'm pretty sure that there was some case law whereby a local council took an individual to court saying that pebbledash -> render wasn't PD. The home owner appealed to the secretary of state and won. The case being "192 Birchwood Road" if you want to try and track it down - that was according to the very knowledgeable bloke who runs this site:

http://planningjungle.com/