Roof and elevation alterations Q & A DCP Section 12.4

This section is mainly concerned with enlargements, improvements or other alterations to a conventional dwellinghouse which affect its roof, including the formation of dormer windows and roof terraces. Elevation alterations including changes to windows and the application of cladding, are also included here. Such works relating to listed houses will be found at (27.2) or (27.3). Additions or alterations relating to existing flat/apartment blocks or at houses converted to flats in the past are considered at (12.5). Rural house extensions, which may involve roof alterations, are specifically dealt with at (12.6). TV/radio aerials and satellite dishes at a dwellinghouse are covered (28.2) and (28.3) and householder micro-generation proposals, such as solar panels and wind turbines, are discussed at (12.7).

Q & A    12.4/10

A local authority imposes a condition on new housing development within or adjacent to conservation areas preventing the erection of TV aerials and satellite dishes. Given that these days most households expect to have a television, with an increasing number requiring satellite dishes, I question the validity of such a condition, especially where it is only by reason of an external aerial that a signal may be gained. Are there any appeal decisions that would throw light on the matter.

A condition may be validly imposed which takes away permitted development (PD) rights or requires permission to be sought for something that would not otherwise be development (such as conventional TV aerials).  This principle is made clear in Circular 11/95 paragraph 86, but  paragraph 87 contains a presumption against such restrictions, citing the criterion of reasonability.  PPG8 on Telecommunications states that  PD rights should not be withdrawn unless there is a real and specific threat to a locality, but also talks of encouraging housing developers to install communal systems.

Unfortunately, I cannot identify any appeal decisions that relate to aerial/dish restriction conditions on new housing permissions in conservation areas. Do readers know of any examples?

We have an application for a roof alteration to change a hipped roof into a gable with a box dormer on the rear slope. My authority does not consider it is permitted development as it materially alters the shape of the dwellinghouse (Class C of the GPDO) but the applicant argues that similar proposals are regarded as falling within Class B. Which is the right interpretation?

The function of Class C is to allow minor alterations to roofs not covered by Class B such as change of materials or the insertion of a rooflight (see Circular 9/95 paragraph 42).  Therefore the restriction in the Order on a Class C permission that it should not materially alter the shape of the dwellinghouse only applies as a restriction in respect of such works. The proposal will have to be tested solely against the criteria in Class B to determine whether it is permitted development.

My colleagues and I are unsure whether planning permission is required for the creation of a light well abutting a house so that a window may be inserted to the basement?

I imagine that this is a dwellinghouse to which householder permitted development rights apply. Class A would seem to give a deemed permission to these works if they are anywhere but between the existing dwelling and the highway, in which case condition A.1(d) would apply.  If the cubic tolerance allowed by A.1(a) has been used up it may be debated as to whether the well itself has a cube to be measured, but the fact that there is no roof may count against such an assessment.

The GPDO states that development on Article 1(5) land which includes conservation areas is not permitted if it consists of the cladding of any part of the exterior of a dwellinghouse with plastic. Does it then follow that UPVC windows in conservation areas require permission?

An ingenious construction, but I somehow doubt that the word "cladding" would be construed in this way if the matter were ever considered in the courts.  However, your question does point to an urgent need to bring replacement plastic windows at conservation area houses within planning control, rather than forcing local authorities to go down the Article 4 Direction route.

A neighbour has erected a rear dormer to their house. This houses faces a highway but the garden does not quite touch it as there is a thin strip of land in front. The local authority hold that planning permission is not required, but are they right?

In England and Wales the GPDO states that permitted development rights do not apply where alterations to the roof of a dwellinghouse extend beyond the plane of any existing roof slope which fronts any highway. A strict reading of these words would be that it is specifically the roof slope that must front the highway. On this interpretation the fact that there is intervening land not in the householder's ownership does not derogate from the fact that this dormer "fronts" the highway in question. The fact that the land is only a "thin strip" further leads me to the conclusion that this council is in error. However, I do not know of a case which is directly relevant, the nearest being the Epping Forest appeal reported in Planning 30 March 2001 page 20.

I am dealing with a case regarding the installation of rooflights into a barn conversion where Part 1 and Part 2 permitted development rights had been removed by condition. My opinion is that rooflights are an alteration to the roof normally covered by Part 1 Class C, and therefore the rooflights will require planning permission. Is my understanding correct?

Before considering the operation of the General Permitted Development Order 1995 it is important to clarify whether there is "development" in the first place.  The Town and Country Planning Act 1990 provides that works that do not materially affect the external appearance of buildings are not development, and the courts have held that part of this test involves the degree to which the works are visible from public vantage points.

Therefore, in the case you quote, your council first needs to form a view on whether the offending roof lights require planning permission at all. If it is judged that they do, the removal of  Part 1 Class C rights precludes any possible deemed permission. As noted in Circular 9/95 paragraph 42 this Class  permits rooflights provided there is no material alteration to the dwellinghouse shape.

I understand that for the purposes of the General Permitted Development Order 1995 (GPDO) "cubic content" is to be measured externally. If this is the case how should the creation of house basements be dealt with, as they do not have any external measurements?

The creation of basements is development as stated in the Town and Country Planning Act 1990 but the GPDO provides a cubic tolerance for the enlargement, improvement or other alteration to a dwellinghouse. However, the Order does not give any specific guidance as to how cubic content is to be measured other than, as you say, that it is to be calculated externally.  I do not have reference to a case where the permitted development status of residential basements has been directly argued. But in a recent appeal case from Tynedale, it was accepted by an inspector that only that part of a conservatory extension on sloping land that lay above ground should be cubed. Using this principle none of a basement totally below ground level would count against permitted development tolerances. Does any reader know of a ruling on this matter?

We are confused with the General Permitted Development Order 1995(GPDO) with regard to Part 1 Class B relating to addition and alterations to the roof of a dwellinghouse. Does this refer to the main roof of the house only, or any roof that belongs to the house? If this could be any part of the roof, how high can an addition be built - the height of the highest part of that roof or the highest part of the highest existing roof?

It is normally held that the word "roof" in relating to Part 1 rights is referring to the totality of the roof areas forming part of a dwellinghouse including any roofs over lower level parts. Support for this view comes from Richmond-upon-Thames London Borough v Secretary of State for the Environment & Neale [1991] where it was held that parapet walls erected on a flat roofed extension to a dwellinghouse were an enlargement of the dwellinghouse permitted by Class B. In Hammersmith and Fulham Council v Secretary of State for the Environment  [1993] it was held that the term "the existing roof" was not limited to a particular part but referred to the highest part of the of the roof structure of the dwellinghouse as a whole. It may be deduced from this that an extension to a lower roof at a house not even connected to the main roof could in theory extend as high as the highest part of the main roof without transgressing the permitted development exception at B1(a).

When dealing with an application for a roof extension where there is a detached garage or outbuilding within five metres of a dwellinghouse, is the volume of that building included when calculating the cubic content of the resulting building?

There is no doubt that the cubic tolerances available under part 1 of the General Permitted Development Order 1995 (GPDO) classes A1(a) and B1(d) are cumulative, but there has been contention as to whether a detached building within five metres should be included, as might be indicated by the provision at class A3(a)(ii). One view was contained in a 1996 lawful development certificate appeal decision from Barnet where a roof extension was argued to be permitted development. It was considered  that the total resulting cubic content to be calculated included the appeal proposal, front and rear extensions, together with a detached garage within 5m of the dwellinghouse and that the totality of these volumes exceeded the 70 cu m tolerance available.

However, in a Reigate and Banstead case reported  in Planning 22 February 2002 p.24  an inspector noted that A3 is stated in the GPDO to be applicable specifically "for the purposes of Class A". He reasoned that there was no justification for applying this provision to another class of permitted development. The logic of the inspector in the latter case was followed by a colleague in a further decision reported in Planning 21 June 2002 p17. Clearly these cases demonstrate two completely different interpretations of the provisions of the GPDO.  I can only ascribe the disparity to yet another failure by the authors of Schedule 2 to express themselves with clarity and precision.

We are presently involved in a matter regarding the creation of a balcony at a dwellinghouse. The proposed change involved an angled roof being lowered and flattened to form an upper floor balcony. Subsequently railings will be attached. I would appreciate your view on whether these works are permitted development.

Class B of the General Permitted Development Order 1995 only covers the enlargement of a dwellinghouse consisting of an addition or alteration to its roof. Your proposal diminishes the bulk of the dwellinghouse and therefore on strict interpretation class B cannot be applicable. However, class C gives a permitted development right for any other alteration to the roof of a dwellinghouse, which would seem to cover your proposal. However, a condition of this deemed permission is that there should be no material alteration to the shape of the dwellinghouse. I rather feel that what is being proposed would be considered to materially alter the shape of the dwelling, and therefore conclude that there are no permitted development rights available.

I am seeking clarification on the following point due to one local authority interpreting the General Permitted Development Order 1995 (GPDO) differently from several others. Class B governs enlargements of a dwellinghouse consisting of an addition or alteration to its roof. In my opinion as long as the relevant criteria are complied with such additions or alterations are permitted development. A local authority has countered that despite total compliance with Class B, under Class C "Any other alteration to the roof of a dwellinghouse", development is not permitted by reason of the proposal resulting in a material alteration to the shape of the dwellinghouse.  I consider that Class B and Class C are mutually exclusive.

You are quite correct and the local authority you cite is guilty of a common misinterpretation. As you say, each Part of the GPDO is a self contained entity and development permitted by one Part is not annulled by the provisions of another. The fault here lies with the heading to Class C which, although it is obviously intended to refer back to Class B, does not explicitly say so.  A useful clarification is contained in Circular 9/95 which states that "Class C deals with roof alterations not involving enlargement. It provides that any alteration to the roof of a dwellinghouse is permitted development, provided that the shape of the dwellinghouse is not materially altered. This does not permit extensions involving roof alterations (which are dealt with in Class B), but would generally permit the replacement of a roof, irrespective of the materials used, or the insertion of roof lights." Class C could also apply to the removal of part of an existing roof as discussed in Casebook Forum 26 July 2002.

Is planning permission required for the installation of a rooflight in a single family dwellinghouse where the rooflight projects 5cm beyond the plane of a roof that fronts a highway?

The first consideration is whether this rooflight is development. Certainly it is a building operation but it is possible that it would be held not to materially affect the external appearance of the building. This would most likely be the case if the light is not readily visible from a public area, using the judgment Burroughs Day v Bristol City Council [1996]

Failing this the rooflight needs to be examined to see if it permitted development. The enlargement of a dwellinghouse consisting of an addition or alteration to its roof is allowed by part 1 class B of the General Permitted Development Order 1995 (GPDO).  Although such an addition is not permitted development if it extends beyond the plane of any existing roof slope which fronts any highway, a 2000 appeal decision from Brent indicated that slightly protruding rooflights were not an "enlargement" and therefore class B did not apply. The inspector therefore reasoned that class C "Any other alteration to the roof of a dwellinghouse" was applicable and as there was "no material alteration to the shape of the dwellinghouse", a rooflight was permitted by this class. Although the extent of the protrusion in the Brent case was not specified. I would have thought that 5cm that you quote would fall within the inspector’s description of "slightly protruding". The answer to your question is that planning permission is not required for the rooflight described.

A constant problem that we have as a local authority concerns the situation where it is proposed to convert a hipped roof to a side gable. Some authorities accept that this is permitted development, others do not. We hold the view that as new brickwork is required to ridge level to form the gable end, this is not an addition or alteration to the roof but rather the building up of a wall of the structure itself.

This matter was dealt with in an appeal case concerning an application for a Lawful Development Certificate back in 1995.  Here an inspector judged that the existing hipped portion of the roof of the house concerned, and onto which the proposed gable end would be constructed, faced towards the side of the property and therefore it could not be said to front the highway. He stated that this was the case notwithstanding the fact that its edge adjoined that of the existing front roof slope, and concluded that the limitation in the GPDO at paragraph B.1 (b) was satisfied.


I read this query with interest as this is one we are constantly faced with. JL rightly highlighted the inconsistency that may exist between local authorities in interpretation. I do however think that the nub of the argument is broader than you think. This is that alterations such as those described, and probably rear box dormers where none of the original roof remains, are enlargements of the dwelling falling under class A. My interpretation of the answer given suggests that the query turns entirely on the interpretation of class B, and would be interested in your comments.

Since my previous answer a further appeal decision has just been issued. This related to refusal of a Lawful Development Certificate for the alteration of a roof from a hip to a gable at a house in Guildford. Here the inspector ruled that Class A was not applicable and the proposal fell squarely within Class B. The council’s argument that the gable wall was not an alteration to the roof, rather a main wall of the house, was rejected and the inspector cited Richmond London Borough Council v Secretary of State for the Environment & Neale [1991] where it was held that a parapet was erected around the flat roof of an existing extension fell within Class B.

We are currently looking at a proposal to install solar panels on a dwellinghouse. The panels will cover 30% of the south facing roof slope, and project above the roof by approx 60mm. Any views on whether this will be permitted development under part 1 class C of the General Permitted Development Order 1995?

This question raises much the same legal issues as discussed in Forum 13 September 2002 p19 with regard to roof lights. Here a case was quoted where an inspector conceded that a roof light which was "slightly protruding" above the plane of a roof was not a class B "enlargement", but neither was it a class C material alteration to the shape of a roof. Consequently the roof light was considered to be permitted development.

Planning permission was granted for the restoration of a conservation area house containing 2 flats back to a single dwellinghouse. A condition was applied removing all permitted development rights within part 1 class A of the General Permitted Development Order 1995 (GPDO). The owner now wishes to insert a rooflight in the roof slope facing the highway. Would this development require permission now that the premises are a single dwellinghouse?

The planning permission has established that this property is now a lawful dwellinghouse to which permitted development rights apply. As only rights under class A have been withdrawn the owner may look to class B and C for a deemed permission. Class B does not apply as the property is within a conservation area, but class C is relevant provided there is no material alteration to the shape of the dwellinghouse. Circular 9/95 paragraph 43 specifically states that this class permits the insertion of rooflights, and cases have shown that minimal projection of such installations does not constitute a material alteration to shape.

My neighbours have built a substantial flat roofed L shaped dormer to the rear that runs just below the ridge of the main roof, and where it joins the party wall it turns 90 degrees along the roof of a secondary extension. As this secondary roof is lower than the main roof this has resulted in a dormer, which protrudes above its ridgeline. The council received a number of complaints but decided it could not reasonably ask for an application as the GPDO says that such a development is permitted if it does not protrude above the highest part of the roof. Can you help?

A similar question has been sent in by RW. The answer is to be found in a Forum reply published on 24 May 2002 where court cases were cited to show that the word "roof" in relation to Part 1 permitted development rights refers to the totality of the roof areas forming part of a dwellinghouse including any roofs over lower level parts. Therefore the highest part of any roof may be taken as the maximum height to which an extension may be taken without transgressing the permitted development exception at Part 1 Class B1(a) of the GPDO.  Unfortunately it is not even open to you to argue that there are no permitted development rights where reliance has been placed on support from a party wall, if an appeal decision from Enfield is followed (see Planning 2 November 2001 p19). Here the technicality that a dormer had strayed outside the curtilage of the dwellinghouse in question was rejected by an inspector.

The inspector’s reasoning regarding an LDC for a dormer (Planning 31 January 2003 p21) and the correct interpretation of the GPDO has sparked intrigue in our office. He opined that a garage within 5m should be taken into account when assessing volume. Under Class B there is no mention of this criteria, this interpretation only relates to Class A. Although there is reference to the "resulting building" under Class B we take that to mean other extensions. This decision seems to go against others.

There are appeal cases to be quoted to support either view on this question, and this current example can only add to the confusion. This point is just one of the many interpretation difficulties which attend the GPDO and I sincerely hope that the current review of the Order being undertaken for the government will recommend radical reforms bringing desperately needed clarity. In the meantime the credibility of the planning system continues to suffer.


Nothwithstanding the "two all" score of appeal cases on the subject, it is instructive to note that Circular 9/95 para. 39 states "Parts contain one of more self standing alphabetically denoted classes….At the end of some parts there are paragraphs which gives interpretations of terms used in those parts. The clear implication of these statements is that one cannot transport criteria from one part to the other. I recall that this was settled some years ago when an LPA attempted to bear the height adjoining the boundary criterion from Part A to Part B.  Moreover in the Encyclopaedia of Planning Law it is commented "They (Class B works) are governed by height and cubic capacity restrictions similar to those in Class A, except that there is no provision corresponding to Class A3 (B), which requires aggregation with any building within five metres of the existing building for calculating the cubic content of the resulting building. This may mean that a larger volume may be created as the result of a roof alteration than by a Class A extension where there are curtilage buildings within five metres."

In the light of both these authorities it would seem that definition of "resulting building" for the purposes of Class B cannot include buildings within five metres and that appeal decisions arrived at on the contrary basis are faulty.

The respondant is quite correct that the Encyclopaedia commentary may be quoted in support of the view that a larger volume may be created as a result of a roof alteration than by a Class A extension where there are curtilage buildings within five metres. But he is wrong to say that contrary appeal decisions are faulty, as further down the same page the commentary also says:"Similarly, in an appeal decision reported at [1996] J.P.L. 68 the Secretary of State, taking into account para. 41 of DOE Circular 9/95, General Development Order Consolidation 1995 and the Richmond upon Thames case, ruled that a proposal for the provision of extra rooms in the roofspace of a dwellinghouse, to provide additional living space within the dwellinghouse, fell to be considered under Class B, notwithstanding that a significant change to the shape of part of the roof would be involved. However, the requirements of sub-para.(d) (resulting building not to exceed cubic content of original dwellinghouse by more than 70 cubic metres) were not satisfied, because of the construction in 1987 of a detached garage within 5 metres of the dwellinghouse. The increases in cubic content allowed by Classes A and B were not to be treated as separate entitlements, but as a cumulative control total for Part 1."

When I first came across this conundrum I was advised by our assistant district solicitor that there was no legal authority from the courts on the question, and that until the courts ruled otherwise LPAs should adopt the more restrictive position on the principle that the Planning Act is itself a restrictive Act.

A further development was a case in Middlesex DCS No.37756557. Here an inspector wrestling with "this rather arcane aspect of the GPDO", and who had made a contrary ruling last year in another case, changed his mind and came down on the side of including a garage with 5m of a dwelling as part of the cubic content calculation.

Further to the second respondents comments, given that there is no decided court authority on the matter, I agree on reflection that my contention as to the status of certain planning appeal decision letters should have been qualified. However, the case for inclusive definition remains questionable and does not appear to have been proven. With due deference to the second respondents assistant solicitor there are many rules as to interpretation. I have always understood that in cases of doubt dealing with the restriction of the freedom of the individual the courts have to be satisfied that it was Parliament’s express intention to take away the liberty in question. I have trawled this point informally with planning solicitor colleagues, who concur. It appears that in the context of Article 8 of the Human rights Act there may be a point that has been overlooked in taking the restrictive view.

Another possible reason to support the first respondents view that the provisions are not transferable is because Class A developments are generally at ground level and therefore concerned with site coverage, whereas Class B structures being roof extensions are not. This is supported within the GPDO itself because the relevance of site coverage is stated in A.1(e) whereas there is no similar concern for site coverage anywhere is Class B. This does not seem to be a coincidence or omission because Class E, which is also concerned with ground level development, states its concern with site coverage in E.1(c).

A glazed screen positioned behind a pair of existing external doors has been enforced against on the basis that there would be unreasonable intrusion on the privacy standards and outlook from nearby dwellings. The doors are like garage doors and open outwards. Is planning permission required for the screen?

I assume that the objection has arisen because what was previously a closed door for most of the time has effectively become a window enabling the occupiers of the building to overlook adjoining residential property. The 1990 Act at sec.55(2)(a) states that works which only affect the interior of a building or those that do not materially affect external appearance, are not development. I cannot find an exact parallel to your case that tests this wording. However, in an appeal case  (Planning 26 July 2002 p19 and p20) it was ruled that a glazed screen, which had been erected behind garage doors at a barn conversion, was not an "external alteration" proscribed by a condition. An inspector reasoned that the garage doors were in fact the approved external face of the barn conversion and therefore the condition had not been breached.  My opinion is that the screen you describe is not development so long as the garage type doors remain in place and operative, but I do not see this as clear cut.  Have any readers an opinion on this fine question of interpretation?


Here is an opinion based solely on my own common sense. You are wrestling with the question of whether putting a glazed screen behind existing doors (or for that matter the opposite, ie adding shutters outside an existing window) might affect the "external appearance" of a building. I suggest that a useful definition of the "exterior" of a building could be "any wholly or partly weatherproof surface which is at or near the bounds of the building".

Given such a definition, there is no reason why a building cannot have two alternative exteriors at the points where there is such a "shutter" arrangement. Unless the shutters are permanently open or shut, the actual situation is that both exteriors are seen from time to time, and it is therefore reasonable to regard both as being part of the external appearance.

So my reply to your enquirer would be that, if the effect of opening the old doors and exposing the new screen (plus the backs of the old doors?) is to make a material change to the external appearance of the building, then PP is needed for installing this new arrangement unless there are permitted development rights.

An LDC was submitted for a roof dormer of under 50 cubic metres. The property has an existing small single story rear addition and a detached garage within 5m of this extension. On the submitted plans the applicant showed that the extension and the garage were to be demolished to meet the permitted development tolerances under Part 1 Class B of the GPDO. The certificate was refused on the basis that the extension and the garage had not actually been demolished and therefore the proposed dormer in conjunction with the extension and garage exceeds the permitted development tolerances and therefore is not lawful. Is this approach correct?

Without more detail it is difficult to conclusively assess whether the extension and particularly the detached garage do in fact count against the permitted development tolerance for this property. As regular Forum readers will know this may be a matter of some controversy. However, assuming that the dormer is not permitted development, but would be so following the removal of the extension and/or the garage, I feel that it would have been reasonable for a certificate to have been issued. Although conditions cannot be applied to an LDC the description of the development certified to be lawful could have specified that the demolitions proposed by the applicant would be carried out previously or concurrently.

A loft conversion of 50m2 is under construction at the moment. However there was an existing rear canopy which if added went over the permitted development limit of 70m3. I was informed by an enforcement officer that there was a breach of control and agree that this was correct.

The canopy should have been removed prior to construction and this has now been undertaken. To remedy the matter an LDC has been submitted to confirm that the dormer is lawful. Is this the correct format to use and will it be successful?

In the period during which the loft works were undertaken and the canopy still existed there was indeed a technical breach of planning control. This is  assuming that the canopy did in fact have a volume that could be measured for the purposes of the GPDO. However, with the removal of the canopy the loft works would become permitted development, but in view of the council’s query it is entirely justifiable for you to ask for an LDC to safeguard your clients position should the property be sold.


I believe that the LDC application you propose should be refused unless it proposes the demolition of the dormer and the canopy extension, prior to the rebuilding of the dormer. This follows the reasoning of the judgment in Watts v  Secretary of State for Transport, Local Government and the Regions [2002] (Planning 31 May 2002 p18).

In Planning 4 July p20 you reported a case involving a requirement to  replace new uPVC windows and a door with a type to be agreed using a neighbour’s property as a model. This seems to be a reasonable and sensible way of getting round the problem that the originals have disappeared, without the harshness of prescribing an exact design. I am sure that many planners would have worded the notice in the same way, but the inspector found the wording uncertain. While I agree, it seems the best way to resolve the problem. What is the recommended way of wording this type of notice?

Circular 10/97 paragraph 2.34 draws attention to the judgment in Kaur v SOS & Greenwich LB [1990] where it was held that a requirement of an enforcement notice providing for the subsequent submission and approval of a restoration scheme introduced an unacceptable degree of uncertainty. The Circular advises that such requirements should be avoided and that specific steps are set out to remedy any breach. It goes on to state that if this is impractical an alternative is to simply require restoration to the condition before the breach took place leaving the developer to comply in accordance with his or her knowledge of that condition.

In the reported case that you mention the inspector used the Kaur ruling in his reasoning and this combined with the fact that it was not certain that the next door windows were in fact similar to those removed from the appeal property, led to the notice being considered void from uncertainty. It follows that in this type of case there should be no problem provided that the requirements of a notice tell the recipient exactly what works need to be done to remedy the breach. In addition if reference is made to the replication of features of the existing building or other nearby properties it is clearly important to establish that these are precisely the same as those which have been lost. I agree with you that such specification through example is by far the best way to indicate to the recipient of a notice exactly what is to be done to put right the breach without resort to tedious architectural specifications.

Planning permission has been granted for a large house and the development is proceeding in accord with the plans, the wall having reached head height. The developer now wishes to add a shallow bay window to the rear, which would be permitted development if construction were further advanced. An application has been submitted and it is believed that this should be related to the bay alone and not be treated as amended plans for the whole house.  The matter of the status of the application is important in this case as a local pressure group is seeking to get the whole permission reviewed. Can you advise?

I see no reason why this proposal for a bay should not be treated for what it is, namely an amendment to approved plans, and am unclear as to how it could be thought of as a device to overturn a development which has commenced in accord with a planning permission.

My council is currently debating whether rear roof extensions that project out onto ‘back addition’ roofs fall within Class A or Class B of Part 1, Schedule 2 of the GPDO 1995. I think many councils treat most extensions that creep along the roof of the rear addition as roof extensions. Is this correct?

All extensions involving roof alterations fall within either Class B (roof enlargements) or Class C (other roof alterations), depending on whether there is a material alteration to the shape of the dwellinghouse.

Do railings above a rear extension of a dwellinghouse require planning permission? I believe that most authorities assess them against Class A of the GPDO. However, in cases where the property is not a dwellinghouse I think the approach is to argue that as railings would materially alter its appearance, they require permission, especially where intended to facilitate the use of a flat roof as a terrace. Is this correct?

Railings erected around flat roofs to form balconies or terraces are often considered to have a material effect on external appearance, although in many cases they will be permitted development by virtue of Classes B and C of Part 1, Schedule 2 of the GPDO. A roof terrace is not permitted by Class A as roof alterations are excluded, although it might be argued that the railings enclose a "volume" which should be counted against the available tolerance. However, in an appeal decided in 1987 it was held that balcony railings did not add any volume to a building while in another in 2000 it was found that the additional volume amounted only to the thickness of the railings themselves.

In Richmond-upon-Thames L.B. v SoS and J.Neale 1991 the High Court considered whether the erection of a parapet wall around the roof of a first floor extension to a suburban house in Surrey was permitted development. It was held that the wall fell to be considered against Class B of the GPDO and as the additional volume in the wall itself, which measured no more than 1 cu. m., did not exceed the relevant allowance, it did not require an express grant of planning permission. However, recommended changes to Part 1 of the GPDO in the recent review commissioned by the ODPM would specifically exclude roof terraces from the order.

It should be noted that in the case of R. (on the application of Cousins) v. London Borough of Camden 2002, the judge held that the erection of iron railings above a flat roof could not be regarded as an enlargement of a dwellinghouse consisting of an addition or alteration to its roof under Class B, Part 1, Schedule 2 of the GPDO 1995 but fell instead to be considered under Class C.


Further to previous views concerning the erection of railings to a balcony being permitted development under either Class B or C of Part 1, Schedule 2 of the GPDO could it not be argued that railings form a means of enclosure under Class A of Part 2 and are therefore subject to the 1m and 2m rule? If the railings were to a ground level patio, Part 2 would apply. Therefore if the patio is raised by virtue of being on top of an extension or other structure, would not measurements from the existing ground level indicate that any railing would require permission?

There is no precedent that supports this proposition. Rather than being considered under Class A of Part 2, as the top of a ground floor extension or structure will be its roof and the railings would result in its alteration, this type of development falls within its own Class, depending on whether there would be a material alteration to the shape of the dwellinghouse. My advice cites a recent court case where it was held that such railings should be assessed under Class C of Part 1.

My authority is currently considering whether a large dormer window at the rear of a house requires planning permission and is seeking clarification on the definition of ‘a roof slope which fronts any highway’ in Class B of the General Permitted Development Order 1995. The roof slope is about 22m from a rear footpath and about 26 m from an adjacent cycle path. However, between the back garden of the house and these paths is an area of amenity land about 3 metres wide, and then an area of highway grass about 10 metres wide. Is this roof slope considered to front a highway?

Although "highway" is not defined in the Order, common law usage is that a highway is a way over which the public are entitled to pass and re-pass, including a footpath. Whether, for the purposes of Class B, a roof slope is considered to front onto a highway is a matter of fact and degree and will concern factors such as distance, orientation and the presence of any other buildings in the intervening space.

In a Yorkshire enforcement appeal case decided by the Secretary of State in 1982, it was concluded that the words "fronts on" must be used in the sense of "faces" and that a Council’s claim that a wall fronted a highway some 33m away was straining the meaning of the term unduly. A similar view might be taken here, although the circumstances are obviously distinguished by the much shorter distance between the roof slope and the highway. A further case of interest can be found in Planning 24 October 2003 p22.

My client has been advised by a planning authority that her proposed loft conversion and dormer window require planning permission as "the part of the building to be enlarged would be within 2 metres of the boundary of the curtilage of the dwellinghouse and would exceed 4 metres in height (Schedule 2 Part 1 Class A (d) of the Town and Country (General Permitted Development) Order 1995". The authority also says that it only considers enlargement of dwellinghouses consisting of an addition or alteration to the roof under Class B if the dormer is set 1m in from the sides of the roof, 1m below the ridge and 1m from the eaves.  I cannot find any such interpretation of the Order in case law, so would appreciate your views on when is a roof extension a roof extension for purposes of Class B of the Order?

Loft conversions and dormer windows fall outside Class A and are assessed under Class B Part 1 Schedule 2 of the GPDO. Both case law and appeal decisions support this view, including one from 1996 where the Secretary of State ruled that proposed living rooms in the roofspace of a dwellinghouse, which included a significant change to the shape of the roof, fell to be considered under Class B. In a more recent case concerning a certificate of lawfulness, an inspector found that a loft conversion was permitted development under this class (Planning 9 January 2004, p20).

Although the GPDO has given rise to considerable difficulties of interpretation over the years, this cannot justify a planning authority imposing its own additional restrictions, such as those to which you refer. Moreover, provided your client’s proposal falls clearly within class B and meets the relevant tolerances, it is not affected by the fact that it offends a stipulation or exception in another, such as that set out at Class A (d).

In considering proposals for solar panels to dwellinghouses in conservation areas and having regard to Class C, Schedule 2, Part 1 of the GPDO 1995, should my authority decide whether such a proposal would constitute a material alteration to the shape of the dwellinghouse in each case or request an application for permission, regardless of the number of panels proposed or their surface area coverage?

This matter is discussed generally at 4.34 of Development Control Practice. In addition, the annex to PPG22 issued in 2002 contains limited guidance on photovoltaic (PV) cells, which convert solar radiation to electricity. It explains that where it is proposed to install these on an existing building, an authority should decide whether they would be a "material alteration to the external appearance of the building". If not, then permission will not be required. But even if the authority considers that it would, express planning permission may not be required because of the rights conferred under the GPDO.

In conservation areas, the guidance says that if PV cells are fitted to a dwellinghouse roof so that in the authority’s view they do not project significantly above the existing roof plane, a planning application may not be necessary, which I take to be an allusion to Class C. It also points out permitted development rights to enlarge the roof of houses do not apply in conservation areas.

Thus solar panels within a conservation area fitted flush with the roof will be permitted development under Class C, irrespective of their surface area, but where they would project significantly above a roof slope permission will be required, as they do not fall within either Class B or Class C, Part 1, Schedule 2 of the GPDO.

Having lost an appeal against my authority's refusal to grant retrospective permission for a dormer window, a householder now queries the need for permission in the first place. A condition of the permission for the original house states that "no wall, fence or structure of any kind" shall be created without the prior consent of the council. It is my understanding that a dormer window is by definition a "structure". Am I right and would enforcement action now be justified?

This is debatable. The condition does not reflect the wording suggested in the model conditions in Circular 11/95. By failing to expressly remove the right to insert windows conferred by the General Permitted Development Order, it could be held to be imprecise and thus fail the six tests set out in the circular. It might be prudent to try to negotiate a solution. "Structure" is not defined in planning law. However, for the purposes of the Order, a building is defined as including a structure but excluding walls and fences. Since a dormer window is a building operation, it follows that it is a structure. Given this fact and that the inspector found that the window is causing material harm, it could be argued that enforcement action would be expedient if all else has failed.

A householder built a single-storey rear extension in 2000 as permitted development. He has recently completed a dormer loft conversion that would be permitted development were it not for the ground floor extension and which he accepts is unlawful. However, would this become lawful if the householder were to remove the rear extension? Or is the lawfulness of a development determined at the time of its completion, once the four-year immunity period has passed or when permission is granted? I can find no authority that governs such a situation and have heard differing opinions. IT.

For the reasons given in my advice to AS (Planning, 24 August, p25), if the ground floor extension is removed in my view this would make the loft conversion lawful. Paragraph 8.3 to Circular 10/97 explains that by virtue of Section 191(2) of the Town and Country Planning Act 1990 uses and operations are "lawful" if no enforcement action may be taken against them and they are not in contravention of any enforcement notice which is in force. This would apply once the time-limit for taking enforcement action has passed or the development is authorised by a permission, including that granted by a development order. PM.  


In Watts v Secretary of State for Transport, Local Government and the Regions 19/4/02, the court held that inherent in the GPDO was a degree of artificiality in that its availability depended on which works were done first. So if between the start of works and their conclusion the building was otherwise enlarged, improved or altered so that the cubic content of the resulting building together with the GPDO works would be more than relevant allowance, the GPDO works would cease to be protected. The court went on to find that prospective cubic content, however imminent, was to be ignored because once prospective cubic content became relevant one would be driven to accept as relevant that which might never exist as cubic content. It follows that prospective demolition must be ignored for the same reasons. The GPDO grants permission for development in the making not for the retention of that which has already been done. A number of inspectors have taken the same view. NW.

Further Response

In his reasoning PM relies on a different case (Planning, 24 August, p25). The two are distinguishable. In IT’s case the rear extension was not demolished before the dormer was constructed. The Article 3(1) permission enables development to commence and, provided it remains within the terms of that permission from the outset and during construction, the development benefits from the permission upon substantial completion. If it exceeds the permitted development limits it cannot benefit from the GPDO permission, is unlawful and can be enforced against. Albeit in different circumstances that is to be found in R (oao Watts) v Secretary of State for Transport, Local Government and the Regions [2002]. So the issue is whether an Article 3 permission can be gained retrospectively. I find nothing in the 1990 Act or the GPDO to suggest that it can and it is now too late to rely on the order’s protection through demolition. Of course a permission under s73A may be sought, but the dormer would stand to be considered on its merits with or without the rear extension. AK.

I want to remove a chimney, including above roof level, on a conservation area house which is not listed or subject to an Article 4(2) direction. My research indicates that neither planning permission or conservation area consent is required, but my council is suggesting that the removal is not permitted development and quote Part 1 Class C of Schedule 2 of the Town and Country Planning (General Permitted Development) Order 1995. LG.

I have a tall chimney stack on a two-storey terraced house which is not listed or in a conservation area. The stack is visible from the public highway and is to be reduced by about one metre leaving the top about 2 metres above ridge height. Would this be classed as development and require planning permission? DC. 


In the case of the removal of a chimney from a house, which is not listed or in a conservation area, planning permission is not required by reason of Part 31permitted development rights. Provided notification requirements are complied with, this deemed permission overrides whatever interpretation may be given to Part 1 Class C. Where a house is in a conservation area, consent is not required provided the demolition involved does not comprise a substantial part of the whole building, as it is hardly likely to be. It is of note that the Heritage White Paper published earlier this year promised to reinstate control of demolition in conservation areas to pre-1997 levels. This proposal is part of the planned merger of the present conservation area consent regime with the mainstream planning system. GH.

Does the fixing of solar panels to a roof require planning permission? The General Permitted Development Order, classes A, B and C are relevant. Our authority has taken the view that planning permission is not required, but other councils take a different view. They are not the most attractive structures and often cover a large section of roof. Conservation areas are not given any different status and we are unlikely to resort to article 4 directions. SB

This is an opportune question to highlight the recent changes to the General Permitted Development Order which came into effect on 6 April 2008. This adds a new part 40 called Installation of domestic microgeneration equipment. It gives permitted development rights for the installation of solar photovoltaics on dwellinghouses (except those which are listed buildings), subject to certain criteria. In your case, installation on a roof must not protrude more than 200 millimetres beyond the roof slope and must not be higher than the roof. In a conservation area, it must not be on a roof slope forming the principal or side elevation of the house and must not be visible from a highway. This amendment order (statutory instrument 2008 No 675) also covers stand alone solar, ground and water source heat pumps and flues forming part of a biomass heating system. This is a welcome clarification of an issue which has been unclear and open to different interpretation, as you have found. GE


I am encouraged from the recent introduction of government legislation intended to relax the need for control over these types of domestic installation, and by implication reducing the number of applications for development control officers to deal with. However, a cursory look at these regulations leaves me with the impression that lawyers are likely to be the principal beneficiary from ensuing interpretation arguments. For example, throughout Part 40, solar panels are not permitted development if these installations "would be visible from a highway", but I ask the question –which highway? The one that bounds the curtilage of the dwellinghouse or some other some distance away, but from which the installation can be seen?  As usual the phrase is not defined, and it will be a matter of interpretation thus lining the pockets of the legal fraternity and bringing further frustration to development controllers.

If somebody informally uses a flat roof as a roof terrace and there are no planning conditions preventing this, can you enforce? Obviously if they have erected railings you can require their removal, but how do you enforce against someone opening their window and sitting on their roof? PB.

To be able to enforce you have, of course, to demonstrate that either operational development or a change of use has occurred. If the premises below the terrace were in non- residential use, e.g. where a flat is above a shop with a rear extension, it would be possible to argue that there had been a material change of use of that roof. In cases where the roof being used is part of the same dwelling or another there would be no material change of use. This issue is considered in more detail in section 12.415 of Development Control Practice. JH.

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