The General Permitted Development Order Part - 1 Class B Q & A DCP Section 4.34

This section deals with the interpretation of the principal provisions of the Statutory Instrument entitled Town and Country Planning (General Permitted Development) Order 1995 - as amended. It also covers the equivalent legislation in Scotland and Wales, both under review at the time of writing. However, information and commentary on the GPDO will concentrate on the English Order, to which radical and controversial changes to Part 1 were made in 2008.

Q & A Part 1 Class B 4.34/103

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.

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.

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).

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.

Response

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, which will be reported more fully in Casebook next week. 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.

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?

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.

Response

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 maisonette, being a self-contained dwelling unit with a separate street-level entrance and no common parts, is on two floors above a ground floor workshop in a detached 3-storey building.  There are no other units in the building. Does such a maisonette qualify as a single dwellinghouse for the purpose of Schedule 2 Part 1 Class B of the GPDO?

The GPDO definition of a dwellinghouse does not assist as it merely refers to the fact that a dwellinghouse does not include one or more flats. However, a flat is defined as a "separate and self-contained set of premises constructed or adapted for use for the purpose of a dwelling and forming part of a building from some other part of which it is divided horizontally." My interpretation of this is that the maisonette you describe is a flat for the purposes of the GPDO and does not therefore possess relevant permitted development rights.

My authority is minded to refuse an application for the retention of a rear dormer on visual amenity grounds. The dormer requires permission because of an existing conservatory and a detached garage within 5m of the dwelling. However, can the applicant now take down part of the garage thus retrospectively making the dormer permitted development?

Whether demolition works may offset usage of permitted development tolerances is a recurring practical difficulty. In a lawful development certificate case from South Oxfordshire in 2001, an inspector held that a proposed two-storey extension was permitted development, even though it exceeded the relevant allowance, as it would be offset by a garage that was part of the original dwellinghouse and to be demolished. Thus, assuming similar action here, it would appear possible to retain the dormer as permitted development.

Response

In response to an enquiry about removing part of a garage to render a dormer extension permitted development. In the case of a dormer, the garage within 5m is irrelevant as the explanatory note to the GPDO indicates in Class B: roof enlargements "They are governed by height and cubic capacity restrictions similar to those in Class A, except that there is no provision corresponding to Class A.3 (b), which requires aggregation with any curtilage building within five metres of the existing building. This may mean 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."

Although the explanatory note to which you refer does not form part of the GPDO, but appears in the commentary in the Encyclopaedia of Planning Law, this advice is clearly correct.

My authority is unsure about the need for permission for domestic balconies when these are formed by railings on an existing flat roof or by the replacement of first floor windows by double doors with railings outside, or through dormer windows with double doors and security railings. I think that providing the railings do not exceed 4m in height above ground level, permission is not required and that the cubic capacity is only in the railings themselves. Can you please clarify?

In R. (on the application of Cousins) v. London Borough of Camden [2002], it was held that the erection of iron railings above a flat roof fell to be considered under Class C, Part 1, Schedule 2 of the GPDO 1995. However, dormer windows with protective railings will constitute an addition or alteration to the roof which should be assessed against Class B. The replacement of first floor windows and the erection of outside railings to form a balcony is likely to materially affect the external appearance of the dwelling and be considered a building operation, to be judged against the limitations under Class A. The 4m height rule applies only to development considered under this class. But you are correct in your understanding that, for the purposes of Class A, the additional volume created amounts only to that of the railings themselves. This means that balconies are often exempt from planning control, as acknowledged in last year’s review of permitted development rights, which recommended that they be excluded from a revised version of the Order.

My authority has received an application for a certificate of lawful use (LDC) for two proposed dormers in the side-facing roof slopes of a detached bungalow. Most of the criteria within Class B of Part 1 of Schedule 2 of the GPDO are satisfied. However a previously free-standing garage within 5m has been linked to the dwelling by a single-storey extension. The cubic capacity of the garage and extension exceeds 70 cubic metres. I take the view that outbuildings should not normally be taken into account in Class B, but am unsure as to whether the most recent extension now effectively makes the garage an extension in itself. Is permission therefore required for the dormer windows?

A similar issue was considered in a recent LDC appeal from Surrey. In that case, the inspector opined that while Class A of the Order had no direct application to the circumstances of the proposed erection of dormer windows within a roof, which he agreed fell to be assessed against Class B, in view of the definition of "resulting building" under paragraph I of Part 1, it was necessary to take any enlargement of the original dwellinghouse under Class A into account when deciding whether the overall permitted development allowance would be exceeded by the proposal. In calculating this, he felt that paragraph A.3 (b) was relevant. This provides that where any part of the dwellinghouse would be within 5m of an existing building within the same curtilage, that building shall be treated as forming part of the resulting building. However, the inspector held that this applied only where a dwellinghouse is extended to within 5m of an existing building, thus reducing the intervening distance. If the same approach is taken here, it follows that the dormer windows would require permission.

A householder has recently installed two solar panels on a roof slope within a conservation area. They project between 12cm and 16cm from the plane of the roof and measure about 1.5m by 2m. The panels appear to require permission because they constitute development and, as they materially alter the shape of the roof, are not permitted by Class B, Part 1, Schedule 2 of the Town and Country Planning (General Permitted Development) Order 1995. I have read the commentary in Development Control Practice, but wondered whether more recent cases provide additional guidance on the point at which a solar panel causes a material alteration to the shape of the roof?

Advice in the annex to PPG22, cancelled by PPS22 issued in August this year, explained that in conservation areas solar panels fitted to a dwellinghouse roof so that in the authority’s view they do not project "significantly" above the existing roof plane may not need permission. However, no guidance was given on what was likely to be considered significant in this context. Clearly this is a matter of fact and degree. Much will depend on the circumstances in each case. Inspectors have previously held that a roof light "slightly protruding" above the plane of a roof was not a class B "enlargement" and solar panels which projected more than 8cm above the roof slope required permission. I can find no recent cases that shed any further light on this matter.

My colleagues and I think solar panels require permission. When assessed under Class C, Part 1, Schedule 2 of the General Permitted Development Order (GPDO) 1995, we consider that the roof panels result in a material alteration to the shape of the dwellinghouse. We have seen cases reported that support this. However, the panels on the rear elevation are very unusual. The house is not listed or in a conservation area and is not subject to any Article 4 direction. What is your view?

As explained in a previous reply, general practice has been to assess solar panels against Class C provisions. If that approach is followed here, it could be argued that the roof panels materially alter the shape of the dwelling and thus require permission. However, the companion guide to PPS22 says that unless they are of an unusual design, involve a listed building or fall in a designated area, solar panels should be regarded as permitted development. They should be treated as being within the plane of the existing roof slope for the purposes of Class B1(b), Part 1, Schedule 2 of the GPDO. This is a more permissive approach than that previously taken. In my view, the panels on the rear wall constitute development and should be assessed under Class A, which grants permission for enlargements and alterations subject to restrictions. Where a panel is within 2m of a garden boundary and higher than 4m, it requires express permission.

Unless prevented by a planning condition, flat roof areas associated with a dwellinghouse can be used for any purpose by the occupier.  Some people put planters on the roof and also use them for sitting out purposes. I have a case where my client's property is directly overlooked by such a roof and the use causes a real problem with intrusion into privacy.  However, the planning authority states that it is powerless to act. The parapet walls surrounding the roof are not compliant with Building Regulations and the roof is not safe to use.  Are you aware of any way or other legislation that can stop the use of the roof?

Sitting out or placing planters on a flat roof does not constitute development. In addition, in accordance with the judgement in Richmond-upon-Thames L.B. v SOS and J.Neale [1991], the parapet walls fall to be considered against Class B of the Town and Country Planning (General Permitted Development) Order 1995 and are unlikely to require an express grant of planning permission. The planning authority’s approach therefore appears correct. But it is possible that any unauthorised openings or replacement windows that have been inserted to facilitate the use of the roof could be considered to have a material effect on the external appearance of the dwelling and thus be deemed to require permission. Apart from any breach of the building regulations, I strongly doubt whether redress is available under human rights, anti-social behaviour or other legislation. Readers’ views are invited.

A 1930's semi-detached dwelling has a detached garage within 5m, which was built in 1950, and a more recent single storey rear extension. The owner now wishes to build a dormer extension. The combined volume of the dormer and the existing extension would fall within the 70 cu m allowance and the dormer would otherwise meet the criteria of Class B, Schedule 2, Part 1 of the GPDO. I think this is permitted development and that is not necessary to add the volume of the garage as well, despite it being built after 1948 within 5m of the dwelling and being 'brought nearer' to the house by the rear extension. Is my understanding correct?

Although approaches vary, the line currently taken by inspectors in comparable cases is that where a garage has been built at the same time as the dwellinghouse, or least before 1948, and is within 5m of the dwellinghouse, it does not count as an "enlargement". It is therefore not necessary to deduct its cubic content from the allowances under Class A, Schedule 2, Part 1 of the Order. But it is generally held that where a dwellinghouse would be extended to within 5m of a detached garage added later, by virtue of condition A.3 (b) the garage should be included within the calculation of the "resulting building" under Class B, despite the fact that the condition does not apply specifically to roof enlargements. If in this case, therefore, the volume of the dormers, the existing extension and the garage together exceed 70 cu m, express permission will be required.

Response

The interpretation given is not the only one that can be made of this ambiguously worded part of the Order. Condition A.3 (b), which requires that existing buildings in the curtilage be included within a calculation of the resulting building where they would be brought within 5m of a proposed development under Class A, is not repeated under Class B. Your advice is directly contradicted by the commentary on the Order in the Encyclopaedia of Planning Law and previous Q&A advice. Such inconsistencies in interpreting the legislation are all too frequent and can only serve to undermine the reputation of planners, since they create the unfortunate impression that they do not understand their own area of purported expertise. I would be interested to know whether this particular anomaly is to be removed as a result of the review of the Order.

My advice reflected more recent appeal decisions where criterion A.3 (b) has been discussed within the context of certificates of lawfulness for dormer extensions. In these it has been held that the limitations on class A become relevant in assessing whether the cubic content of the "resulting building" would be exceeded by the tolerances set out under Class B (d). Paragraph I of Part 1 defines "resulting building" as meaning "the dwellinghouse as enlarged, improved or altered, taking into account any enlargement, improvement or alteration of the dwellinghouse, whether permitted by this Part or not". The view has been taken therefore that the effect of paragraph I is to set a single, cumulative limit under any class in Part 1 which results in the enlargement of the dwellinghouse. While Class A has no direct bearing on a dormer extension, the definition of the resulting building in paragraph I means that any enlargement of the original dwellinghouse under Class A must be taken into account in assessing whether the tolerance under Class B(d) would be exceeded by a proposal. The difficulties in applying Criterion A.3 (b) were highlighted in the review of permitted development rights commissioned by the ODPM in 2003. However, the report’s recommendations were not mentioned in the planning minister’s recent statement announcing a new householder development consents review.

Do you know when Class A.3 of the Town and Country Planning (General Permitted Development) Order 1995 came into being? I need to ascertain the exact date in order to know whether a particular garage, that is neither original nor built prior to 1948 and within 5m of the curtilage of the dwellinghouse, is required to be included within the calculations for determining a roof extension under class B. My understanding is that if the garage was constructed prior to the implementation of Class A.3 legislation it would not be treated as an enlargement to the property.

The Order came into force on 3rd June 1995. However, this is irrelevant as Article 1 makes clear that, except in the definition of "original", references to "existing" in relation to any building means existing immediately before the carrying out of the development described in the Order. The application of paragraph A.3(b) to roof enlargements has been discussed before. Inspectors have held that the limitations at A.3(b) become relevant in assessing whether the cubic content of the "resulting building" would be exceeded by the tolerances set out under Class B (d). But in this case the garage will only count where an existing or proposed extension has the effect of reducing the distance between it and the dwellinghouse to within 5m.

Response

You indicated that a detached garage may count towards cubic volume when assessing a roof extension under Class B, Part 1, Schedule 2 of the General Permitted Development Order 1995. I thought this only applied to extensions under Class A, since although the Interpretation of Class A at A.3 (b) mentions this, there is no such similar reference under Class B. Thus whilst an existing attached extension would count towards volumetric limits for a Class B extension, a detached building within 5m would not. Can you comment on this further?

Further Response

The application of the detailed provisions to Classes A and B and the circumstances when existing detached buildings should count against permitted development allowances continues to create considerable confusion amongst readers, as is evidenced by the frequency with which this matter re-appears. It is to be hoped that this is something that will be clarified in the government’s Householder Development Consents Review and publication of urgently needed amendments to the Order, following recommendations made in September 2003. In the meantime, the consistent approach now being taken by inspectors is as follows. Paragraph B.1(d) provides that the cubic content of the "resulting building" following a roof enlargement should not exceed the cubic content of the "original house" by certain specified amounts. "Resulting building" is defined under the Interpretation of Part 1 at paragraph I as meaning the dwellinghouse as enlarged, improved or altered, "taking into account any enlargement, improvement or alteration to the original dwellinghouse", whether permitted by this Part or not. It therefore follows that it is necessary to consider whether there has been any enlargement to the original dwellinghouse under Class A and, in accordance with paragraph A.3(b), whether that has brought it to within 5m of any existing curtilage building. Where this has occurred, the detached building must be taken into account when assessing whether a roof enlargement would exceed the relevant limitation under paragraph B.1(d).

You have indicated that a detached garage may count towards cubic volume when assessing a roof extension under Class B, Part 1, Schedule 2 of the General Permitted Development Order 1995. I thought this only applied to extensions under Class A, since although the Interpretation of Class A at A.3 (b) mentions this, there is no such similar reference under Class B. Thus whilst an existing attached extension would count towards volumetric limits for a Class B extension, a detached building within 5m would not. Can you comment on this further?

The application of the detailed provisions to Classes A and B and the circumstances when existing detached buildings should count against permitted development allowances continues to create considerable confusion amongst readers, as is evidenced by the frequency with which this matter re-appears. It is to be hoped that this is something that will be clarified in the government’s Householder Development Consents Review and publication of urgently needed amendments to the Order, following recommendations made in September 2003. In the meantime, the consistent approach now being taken by inspectors is as follows. Paragraph B.1(d) provides that the cubic content of the "resulting building" following a roof enlargement should not exceed the cubic content of the "original house" by certain specified amounts. "Resulting building" is defined under the Interpretation of Part 1 at paragraph I as meaning the dwellinghouse as enlarged, improved or altered, "taking into account any enlargement, improvement or alteration to the original dwellinghouse", whether permitted by this Part or not. It therefore follows that it is necessary to consider whether there has been any enlargement to the original dwellinghouse under Class A and, in accordance with paragraph A.3(b), whether that has brought it to within 5m of any existing curtilage building. Where this has occurred, the detached building must be taken into account when assessing whether a roof enlargement would exceed the relevant limitation under paragraph B.1(d).

My local planning authority is confused as to which Class under the General Permitted Development Order 1995 it should consider a proposed change in the roof style of a property from hipped to gable and the creation of a room in the roof space. Would this require express permission?

All enlargements of a house comprising an addition or alteration to its roof should be assessed against Class B, Part 1, Schedule 2 of the Order, as explained at paragraph 41 of Circular 9/95. On Article 1(5) land such as national parks, areas of outstanding natural beauty and conservation areas, roof extensions to houses are not permitted development. Elsewhere, roof extensions that project beyond the plane of a roof slope fronting a highway are not permitted development. Otherwise, roof extensions may be permitted development, subject to certain restrictions on their height and increase in volume.

Response

My previous authority held that the works described by the questioner are not permitted development under Class B. Which interpretation is correct?

The enlargement of a house by extending the roof in this way cannot fall to be judged against Class A because criterion A.1(h) expressly provides that development is not permitted by Class A if "it would consist of or include an alteration to any part of the roof". Neither is it covered by Class C because this deals only with alterations that would not materially alter the shape of the dwellinghouse. Therefore the works should be assessed against Class B. Provided the roof enlargement would not exceed the highest part of the dwellinghouse or contravene the other limitations under this Class, it would be permitted development. My advice is supported by a decision from Surrey in 2002, which considered a lawful development certificate for a scheme that included extending a hipped roof at the side of a semi-detached dwelling to form a gable end (DCS No: 31259684). The local planning authority argued that Class B did not apply because the extension involved works other than to the roof, namely the raising of the gable wall. The inspector rejected this submission. In his view, the nature of the proposed works in relation to the dwellinghouse at the time of the application should be considered and not the situation after completion. The inspector held that the scheme involved the provision of additional accommodation under an extended roof and did not, as a matter of fact and degree, exceed what might be regarded as an addition or alteration to the roof. He found nothing in Class B that would exclude the works from the class merely because the extension would terminate in a vertical gable end rather than a sloping hipped roof. The inspector felt that this conclusion was consistent with the judgment in London Borough of Richmond-upon-Thames v SOS & Neale [1991], where it was held that a vertical wall erected on the flat roof of an existing extension was an alteration of the roof permitted under Class B. A similar decision was reached in another case in 2002 involving the same planning authority (DCS No: 32542728).

When assessing whether permission is required for a dormer extension under Class B, Part 1, Schedule 2 of the General Permitted Development Order 1995, there is some disagreement at my authority over the need to consider detached buildings within 5m of a dwelling. The Order suggests that they should only be included in the permitted development allowance when assessing enlargements under Class A, as this requirement is not repeated under Class B. Is this right?

Paragraph B.1(d) provides that the volume of the "resulting building" following a roof enlargement should not exceed the volume of the original house by specified amounts. "Resulting building" is defined under the interpretation of Part 1 at paragraph I as meaning the dwellinghouse as enlarged, improved or altered, "taking into account any enlargement, improvement or alteration to the original dwellinghouse", whether permitted by this part or not. It is necessary to consider whether there has been any enlargement to the original dwellinghouse under Class A and whether that has brought it to within 5m of any existing curtilage building. Where this has occurred, the detached building must be taken into account when assessing whether a roof enlargement would exceed the relevant limitation.

A local authority argues that alterations to form a room above a flat-roofed rear addition to a dwelling that is below its main roof line is not permitted development. This seems to conflict with the approach taken in London Borough of Hammersmith and Fulham v Secretary of State for the Environment and Davison [1993]. Do you agree?

In this case the court held that the phrase "exceed the height of the highest part of the existing roof", which is a limitation that appears in both Classes A and B, Part 1, Schedule 2 of the General Permitted Development Order 1995, refers to the highest part of the roof as a whole, not just part of it. So provided the additional room satisfies the criteria of Class B.1, express permission will not be required.

A neighbour has converted a first-floor window within 2m of the curtilage of my house into a door to provide access to a flat roof over an extension built as permitted development. He also placed decking on the roof and erected a wooden balustrade fixed to the main wall to create a large roof terrace. The structure overlooks my back garden and bathroom and causes noise disturbance when used. The local authority claims that the balustrade encloses space and is within permitted limits, so express permission is not required. After I referred to the case study that follows paragraph 5.22 of the 2003 review of permitted development rights, which mentions an appeal decision where it was held that a similar scenario would require permission, the authority told me that counsel had advised that the inspector's decision was wrong. Do you agree?

No material change in use has occurred. In London Borough of Richmond-upon-Thames v Secretary of State for the Environment and Neale [1991], the court held that a parapet wall on a flat roof was an enlargement of the dwellinghouse under Class B, Part 1, Schedule 2 of the General Permitted Development Order 1995 rather than an alteration under Class A. It also ruled that while the parapet wall did not enclose any space, the cubic content of the structure itself should be assessed when considering whether the relevant volumetric limit had been exceeded. So in your case, while I have doubts that the balustrade could be said to enclose any space, it will not require express permission if its cubic content, when added to the volume of the existing extension, is within the relevant limit set by paragraph B.1 and satisfies the remaining criteria. The conversion of the window to a door would only be development for the purposes of planning control if it materially affects the dwelling's external appearance. In the event that it does, it could be argued that it requires permission because it is caught by condition (d) of Class A, since it would no longer be a window but a door. Neither term is defined in planning legislation. The 2003 review recommended that works resulting in the creation of a roof terrace be excluded from permitted development rights.

A roof lights manufacturer has developed a window that lies flush with the roof slope when shut but opens up to form a small balcony. A householder wishes to install such a window at a house in a conservation area with no highway at the rear. Express permission would not normally be required for a standard roof window. But it might be argued that when the balcony window is open the house is enlarged or its shape is altered. Such a window raises loss of privacy issues. It seems that window technology is running ahead of the General Permitted Development Order 1995. What is your opinion?

When such a window is closed it would be permitted under Class C, Part 1, Schedule 2 of the Order. If it is opened only occasionally, it could be argued that this would be de minimis. But if it is often used as a balcony, it would seem appropriate to treat it as a roof enlargement to be assessed against the provisions of Class B. In that event, permission would be required to insert it into a roof in a conservation area.

My authority has received an enquiry from a member of the public regarding the replacement of an existing flat roof with a pitched roof. The single storey element is to the side of a two-storey residential property. Would this be dealt with reference to Class A or Class B of the General Permitted Development Order 1995 and are there any restrictions as to height?  Criterion (a) of Class B it states that ‘any part of the dwellinghouse, as the result of the works, exceed the highest part of the existing roof’, but does this refer to the main two-storey part or just to the specific part of the single storey element. AJ.

The correct Class is B as criterion (h) at A1. excludes works which "consist of or include an alteration to any part of the roof."  The court case Hammersmith & Fulham London Borough v Secretary of State for the Environment [1993] confirmed that the ‘highest part of the existing roof’ refers to the dwelling as a whole and not the particular part of the roof where works are to be carried out.GH.

Would you clarify the way that the volume limits for dormer windows under class B, part 1, schedule 2 of the General Permitted Development Order 1995 should be assessed, particularly where there is a garage within 5m of the dwellinghouse? My understanding is that the provisions of paragraph A.3(b) under class A do not apply and that only additions to the original dwellinghouse should be taken into account. Is this correct?

The application of this provision continues to cause difficulties and has given rise to inconsistencies in approach. Paragraph B.1(d) provides that the volume of the "resulting building" following a roof enlargement, which would include dormer windows, should not exceed the volume of the original dwellinghouse by specified amounts. The "resulting building" is defined under the interpretation of part 1 at paragraph I as meaning the dwellinghouse as enlarged, improved or altered, "taking into account any enlargement, improvement or alteration to the original dwellinghouse", whether permitted by this part or not. So it is necessary to consider whether there has been any enlargement to the original dwellinghouse under class A and, in accordance with paragraph A.3(b), whether that has brought it to within 5m of any existing curtilage building. However, the practice of inspectors recently has been that where any garage within 5m of a dwellinghouse was built either before 1 July 1948 or at the same time as the original dwellinghouse, it will not be included within the "resulting building" and deducted from the permitted development allowance.

Does class B of part 1 of the General Permitted Development Order 1995 refer only to the dwelling as originally built, or can the alterations be carried out to the roof of an extension (subject to compliance with the relevant limitations)? CD.

Yes, say, the addition of a dormer to an extension that has already been built as permitted development could also be permitted development as class B of part 1 of schedule 2 of the General Permitted Development Order 1995 would cover it. JH. 

When is a dormer a dormer and when is it an extension to a house? Double dormers have been added to two L-shaped houses, i.e. an L-shaped structure comprising a dormer on the main house and one over the rear part. The resulting structures are neither sympathetic to the design of the houses, nor attractive and are harmful to the area’s appearance.  It is claimed that as dormers they comply with the permitted development criteria.  I cannot accept this and would like to run a case that they are extensions to the houses.  Have you any thoughts? JW

Class B of part 1 of schedule 2 of the General Permitted Development Order 1995 as amended last year permits "the enlargement of a dwellinghouse consisting of an addition or alteration to its roof". Whilst the vast majority of alterations that occur under class B are either conventional dormers or hip-to-gable conversions, the order does not preclude other forms of extension. Thus, provided the double dormers meet the criteria in class B, such as the size limits and being 20 cm from the original roof eaves, they would be permitted development.
In the case raised by JW it should be noted that the rear protrusions on the house have pitched roofs. It has been put to me, and this suggestion seems reasonable, that, if the rear protrusion has a flat roof, a double dormer fails to meet the requirement that it should be 20 cm from the roof eaves. JH.

Under class B of part 1 schedule 2 of last year’s General Permitted Development Order Amendment would a new rear dormer be allowed to have a ‘juliet balcony’, i.e. one where the guard rail is immediately adjacent to the doors and which does not project, or is this classed as a balcony?  It seems there would be no objection to the insertion of inwards opening doors but would the railings, which would be flush with the wall, require permission? JS.

The Amendment is not clear on this issue, but the inspector in a recent appeal decision in Yorkshire (DCS Reference 100-063-977) took the view that a juliet balcony would be permitted development. JH.

Is adding a pitched roof to an existing flat roof on a house permitted development under class B of part 1 of schedule 2 of the General Permitted Development Order 1995 as amended? If so, does the phrase "the highest part of the existing roof" relate the highest part of the roof on any part of the property or just the part to which is to be extended? Also, the Order precludes extensions which "extend beyond the plane of any existing roof slope which forms the principal elevation of the dwellinghouse and fronts a highway". Does a flat roof have a plane, as most flat roofs actually have a slope? TC.

Yes, adding a pitched roof to an existing flat roof would be covered by class B. The case Hammersmith and Fulham London Borough. v Secretary of State for the Environment 1993 indicates the highest part of the roof is the overall highest part. Even if a "flat" roof slopes at a slight angle as is normally the case to facilitate drainage, I would not interpret this as having a "plane", but sometimes a pitched roof being added to a flat one could project forward of the plane of a roof onto which it abuts and therefore not be permitted development. JH.

We have recently received planning permission for 16 B1 units varying from 500 to 1500 sq ft.  A condition states ‘The premises shall not be used other than for the purposes defined in Class B1 of the Town and Country Planning (Use Classes) Order 1987 as amended by the Town and Country Planning Use Classes (Amendment) Order 2005.’.  This seems to be simply stating the use applied for and does not seem to be withdrawing our permitted development rights.  Given that the General Permitted Development Order allows a change of use to B8 if under 235 sq m, it seems reasonable that individual units could be changed to B8 if the need arises.  Do you agree? IG.

No, the wording of the condition used is typical of that which authorities impose when they wish to prevent changes of use to another use class which otherwise might be permitted development. JH.

In Class B1(b) of the amended General Permitted Development Order (GPDO) a dormer would require permission where it extends "beyond the plane of any existing roof slope which forms the principal elevation of the dwellinghouse and fronts a highway". My client wishes to construct a rear dormer on a terraced house with a private rear vehicular access. The local authority considers the rear access is a highway and, being visible from a highway, the rear elevation of the house is the principal elevation. Surely in these circumstances the dormer would be permitted development.  IP.

As section 4.3442 of Development Control Practice explains, generally a rear private access road would not be considered a highway. If in the circumstances of this case the council can justifiably argue it is a highway, the rear elevation would not in any event be the principal elevation. A significant effect of the GPDO amendment is that extensions to dwellings backing onto highways often now no longer require permission. JH.

We have recently had a certificate of lawfulness refused for a two-storey rear extension to a house as it would not comply with class B of part 1 of the General Permitted Development Order 1995 (as amended) as the cumulative roof volume of both the proposed and an existing extension would exceed 50 cubic metres. In its decision the council refers to Page 28 of "Permitted development for householders - Technical Guidance" which states: "Where an extension to a house under Class A includes works that would require an alteration to the existing roof of the house (e.g. where the roof of the extension joins the existing roof), the alterations to the existing roof of the house will need to meet the requirements of Class B or C (as appropriate) in order to be permitted development". We revised the scheme to give the extension an independent roof that would not join the original roof; however our second application was refused due to non-compliance with class B. I would appreciate your thoughts. PC.

I am not aware of any appeals dealing with the scenario in your second application, but if the extension roof does not alter the existing roof I would not consider class B would apply. I would suggest lodging an appeal and we would be very interested to hear the outcome. JH.


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