IMPORTANT: DCLG has updated its “Permitted development rights for householders – Technical Guidance” document (April 2016) …

[NOTE: For other updates to the "Technical Guidance" document, please view the following posts:
- This post for the January 2013 updates.
- This post and this post for the October 2013 updates.
- This post for the April 2014 updates.
- This post for the April 2016 updates.
- This post for the April 2017 updates.
- This post for the September 2019 updates.]

Introduction:

The Department for Communities and Local Government (DCLG) has updated its "Permitted development rights for householders - Technical Guidance" document (note: this document provides advice relating to Part 1 of the GPDO). As such, the current and previous versions of the "Technical Guidance" document are now as follows:

April 2016: Permitted development rights for householders - Technical Guidance (pdf) (link).
April 2014: ~~Permitted Development for Householders - Technical Guidance~~ (pdf).
October 2013: ~~Permitted Development for Householders - Technical Guidance (as amended on 17/12/2013)~~ (pdf).
October 2013: ~~Permitted Development for Householders - Technical Guidance (as amended on 20/11/2013)~~ (pdf).
October 2013: ~~Permitted Development for Householders - Technical Guidance (as amended on 29/10/2013)~~ (pdf).
January 2013: ~~Permitted Development for Householders - Technical Guidance~~ (pdf).
August 2010: ~~Permitted Development for Householders - Technical Guidance~~ (pdf).

The main differences between the current version (April 2016) and the previous version (April 2014) of the "Technical Guidance" document are as follows:

Dwellinghouse granted planning permission by Part 3 Class M, N, P, PA, or Q (pages 4-5, 10, 33, 38, 40-41, and 47-49):

Since the previous version of the "Technical Guidance" document was published in April 2014, limitations A.1(a), B.1(a), C.1(a), D.1(a), E.1(a), F.1, G.1(a), and H.1(a) have been amended when the GPDO 1995 was replaced by the GPDO 2015 (link) on 15/04/2015, and amended by SI 2016 No. 332 (link) on 06/04/2016. For info, these limitations now set out that Part 1 Classes A to H do not apply if permission to use the property as a dwellinghouse has been granted only by virtue of Part 3 Class M, N, P, PA, or Q.

As such, on pages 4-5 of the "Technical Guidance" document, in the section titled "Introduction", the previous advice relating to Part 3 of the GPDO has been replaced with the following:

"These rights do not apply to houses created through the permitted development rights to change use, set out in Classes M, N, P, PA, and Q of Part 3 of Schedule 2 to the Order, from shops, premises offering financial and professional services, betting shops, pay day loan shops, amusement arcades, casinos, launderettes, premises offering storage or distribution services, light industrial premises and agricultural buildings; or any houses which are flats. In these cases planning permission should be sought."

Furthermore, on pages 10, 33, 38, 40-41, and 47-49 of the "Technical Guidance" document, new sections have been inserted for each of the above limitations.

As a result of the above amendment, the following conclusion has been added to the "Dwellinghouse granted planning permission by Part 3 Class M, N, P, PA, or Q" topic of the "GPDO Part 1 (All Classes) - LDC Appeal Decisions" document on this website:

These rights do not apply to houses created through the permitted development rights to change use, set out in Classes M, N, P, PA, and Q of Part 3 of Schedule 2 to the Order, from shops, premises offering financial and professional services, betting shops, pay day loan shops, amusement arcades, casinos, launderettes, premises offering storage or distribution services, light industrial premises and agricultural buildings; or any houses which are flats. In these cases planning permission should be sought.
[Source: Permitted development rights for householders - Technical Guidance].
[This advice is since April 2016].

The definition of the term "height" (pages 6 and 11):

On page 6 of the "Technical Guidance" document, in the section titled "General issues", the definition of the term "height" previously included a footnote that stated that "ground level" means natural ground level. This footnote has now been removed. Similarly, on page 11, in the section relating to limitation A.1(c), the previous reference to "the natural ground level" has now been replaced with a reference to "the ground level".

In my opinion, it's likely that the above amendment was made primarily to align the wording of the advice more closely with the wording of article 2(2) of the GPDO 2015, rather than to imply that "ground level" doesn't mean natural ground level. Indeed, it should be noted that the "Height" topic of the "GPDO Part 1 (All Classes) - LDC Appeal Decisions" document currently contains 10 appeal decisions that state, or imply, that "ground level" means natural ground level. However, even if it's assumed that "ground level" still means natural ground level, it's frustrating that this interpretation now needs to be supported via appeal decisions, rather than via the "Technical Guidance" document.

As a result of the above amendment, the following conclusion within the "Height" topic of the "GPDO Part 1 (All Classes) - LDC Appeal Decisions" document on this website has been updated to show that the "Technical Guidance" document no longer supports this conclusion:

When measuring the height of a structure, “ground level” means natural ground level.
~~[Source: Permitted development rights for householders - Technical Guidance].~~
[Note: This advice was added to the August 2010 version of the above document, but was subsequently removed from the April 2016 version].

The definition of the term "highway" (page 6):

Since the previous version of the "Technical Guidance" document was published in April 2014, the definition of the term "highway" (and the associated definition of the phrase "unadopted street") has been inserted into Part 1 paragraph I of the GPDO when the GPDO 1995 was replaced by the GPDO 2015 (link) on 15/04/2015. For info, these new definitions state the following:

""highway" includes an unadopted street or a private way;"

""unadopted street" means a street not being a highway maintainable at the public expense within the meaning of the Highways Act 1980."

As such, on page 6 of the "Technical Guidance" document, in the section titled "General issues", the following definition of the term "highway" (and the associated definition of the phrase "unadopted street") has been inserted:

""Highway" – is a public right of way such as a public road, public footpath and bridleway. For the purposes of the Order it also includes unadopted streets or private ways."

""Unadopted street" – means a street not being a highway maintainable at the public expense within the meaning of the Highways Act 1980."

As noted in this previous post, it's difficult to assess the significance of these new definitions.

It should be noted that, although the "Technical Guidance" document states that "For the purposes of the Order [the term "highway"] also includes unadopted streets or private ways", in actual fact the definition within Part 1 paragraph I of the GPDO applies only "For the purposes of Part 1".

It should also be noted that article 2(1) of the GPDO 2015 defines the phrase "private way" as "a highway not maintainable at the public expense and any other way other than a highway". If the latter part of this definition is combined with the latter part of the above definition of the term "highway", then the result is that, for the purposes of Part 1, a ""highway" includes ... any other way other than a highway". As such, it will be interesting to see how Inspectors interpret the term "highway" within the post-15/04/2015 version of Part 1 of the GPDO.

Finally, for reference, the previous versions of the "Technical Guidance" document didn't include a definition of the term "highway" within the above section (i.e. the section titled "General issues"), but did include the following advice within two subsequent sections of the document:

"A highway will usually include public roads (whether adopted or not) as well as public footpaths and bridleways, but would not include private driveways."

As a result of the above amendment, the following conclusion has been added to the "Highway" topic of the "GPDO Part 1 (All Classes) - LDC Appeal Decisions" document on this website:

A "highway" is a public right of way such as a public road, public footpath and bridleway. For the purposes of the Order it also includes unadopted streets (i.e. a street not being a highway maintainable at the public expense within the meaning of the Highways Act 1980) or private ways.
[Source: Permitted development rights for householders - Technical Guidance].
[This advice is since April 2016].

The definition of the term "curtilage" (page 7):

On page 7 of the "Technical Guidance" document, in the section titled "General issues", the following definition of the term "curtilage" has been inserted:

""Curtilage" - is land which forms part and parcel with the house. Usually it is the area of land within which the house sits, or to which it is attached, such as the garden, but for some houses, especially in the case of properties with large grounds, it may be a smaller area."

For reference, the previous versions of the "Technical Guidance" document included the following advice within a subsequent section of the document:

"What is defined as the curtilage for a particular house will vary according to a number of factors, but in most cases it will comprise the area of land around the original house (ie what is understood to be the garden/grounds of the house). But the curtilage may be a smaller area in some cases, especially in the case of properties with large grounds set in the countryside."

One significant difference between the above two paragraphs is that the new definition now refers to the area of land within which the "house" sits, rather than the area of land around the "original house". It may be the case that this term original was removed to accord with the interpretation, as concluded by the appeal decision "December 2013 - Code a00439", that the phrase "the curtilage of the dwellinghouse" refers to the curtilage of the "existing" dwellinghouse, rather than the curtilage of the "original" dwellinghouse.

As a result of the above amendment, the following conclusion has been added to the ""Curtilage" and "Development within the curtilage of a dwellinghouse"" topic of the "GPDO Part 1 (All Classes) - LDC Appeal Decisions" document on this website:

The "curtilage" is land which forms part and parcel with the house. Usually it is the area of land within which the house sits, or to which it is attached, such as the garden, but for some houses, especially in the case of properties with large grounds, it may be a smaller area.
[Source: Permitted development rights for householders - Technical Guidance].
[This advice is since April 2016].

The definition of the phrase "enlarged part of the house" (page 7):

On page 7 of the "Technical Guidance" document, in the section titled "General issues", the following definition of the phrase "enlarged part of the house" [sic] has been inserted:

""Enlarged part of the house" - is the part(s) of a dwellinghouse comprising any enlargements of the original house, whether built under permitted development rights or following any application for planning permission, and whether the enlargement is undertaken on a single occasion or added incrementally."

The insertion of the above definition is particularly significant, because 1) the legislation does not define this phrase, and 2) the previous versions of the "Technical Guidance" document did not define this phrase.

For info, one of the significant ambiguities of the legislation relates to the situation where a proposed extension would be attached to an existing extension. For example, suppose that part of the original rear wall of a terrace house is covered by an existing single storey rear extension with length 4.5m, and it's proposed to cover the remaining part of the original rear wall with a proposed single storey rear extension with length 3.0m. Would such works be contrary to Part 1 Class A, on the basis that the combined structure would have length greater than 3.0m, or would such works accord with Part 1 Class A, on the basis that the proposed extension (in itself) would have length no greater than 3.0m? For reference, "The enlarged part of the dwellinghouse" topic of the "GPDO Part 1 (All Classes) - LDC Appeal Decisions" document currently contains 23 appeal decisions that state, or imply, the former interpretation versus 8 appeal decisions that state, or imply, the latter interpretation. The above new definition within the "Technical Guidance" document, which refers to "any enlargements of the original house", implies the former interpretation (i.e. that the phrase "the enlarged part of the dwellinghouse" applies to the combined structure).

It should be noted that the above 23 appeal decisions, which support the interpretation that the phrase "the enlarged part of the dwellinghouse" applies to the combined structure, relate to situations where the proposed extension would be attached to the existing extension. However, the new definition within the "Technical Guidance" document, with its relatively inclusive wording, raises the question of whether this phrase would also apply to the combined structure in situations where the proposed extension would be separated from the existing extension. In my opinion, this would not be the case, particularly noting that the information on pages 27 and 28 of the "Technical Guidance" document still implies that there is a significant difference between situations where extensions would be attached to one-another versus situations where extensions would be separated from one-another.

As a result of the above amendment, the following conclusions have been added to "The enlarged part of the dwellinghouse" topic of the "GPDO Part 1 (All Classes) - LDC Appeal Decisions" document on this website:

The "enlarged part of the house" [sic] is the part(s) of a dwellinghouse comprising any enlargements of the original house, whether built under permitted development rights or following any application for planning permission, and whether the enlargement is undertaken on a single occasion or added incrementally.
[Source: Permitted development rights for householders - Technical Guidance].
[This advice is since April 2016].
Where a proposed extension would be attached to an existing extension, then the phrase “the enlarged part of the dwellinghouse” applies to the combined structure. [Note: In other words, the combined structure should be assessed against those limitations and conditions of Class A that apply to the enlarged part of the dwellinghouse].
[Source: Permitted development rights for householders - Technical Guidance].
[This advice is since April 2016].
[Note: The information on page 7 ("April 2016" version) of the above document implies this conclusion].

A detached structure, whether original or non-original, counts towards the 50% limit of A.1(b) and E.1(b) (pages 10 and 41):

On page 10 of the "Technical Guidance" document, in the section relating to limitation A.1(b), the previous advice has been replaced with the following:

"The 50% limit covers all buildings so will include existing and proposed outbuildings as well as any existing or proposed new extensions to a house. It will exclude the area covered by the original house but will include any later extensions or any separate detached buildings, even where they were built prior to 1948, or if the house was built after that date, built when the house itself was built (for example a detached garage or garden shed)."

On page 41, in the section relating to limitation E.1(b), a similar replacement has been made.

For reference, the previous advice stated the following:

In my opinion, although the above previous advice and the above current advice are both poorly written, their meaning is effectively the same - i.e. that a detached structure, whether original or non-original, counts towards the 50% limit of A.1(b) and E.1(b).

As a result of the above amendment, the following conclusion has been added to the "A.1(b)" and "E.1(b)" topics of the "GPDO Part 1 (All Classes) - LDC Appeal Decisions" document on this website:

For the purposes of A.1(b) and E.1(b), a detached structure (e.g. a detached garage) built prior to 1948 (or built at the same time as the house, if the latter was built after 1948) is not part of the “original dwellinghouse”. [Note: In other words, a detached garage will always count as having used up some (or all) of the 50% limit, regardless of when it was built].
[Source: Permitted development rights for householders - Technical Guidance].
[This advice is since April 2016].

The height of the extension versus the "highest part of the [existing] roof" (page 11):

On page 11 of the "Technical Guidance" document, in the section relating to limitation A.1(c), for the phrase "the height of the part of the dwellinghouse enlarged", the previous advice stated that this "should include any protrusions above the roof such as parapet walls etc", whereas the current advice states that this "may include any protrusions above the roof such as parapet walls etc".

For info, the above advice is relevant to the situation where the main roof of an existing house has raised parapet walls (e.g. along the party walls) that are higher than the main ridge-line, and the question of whether limitation B.1(b) would allow (say) a dormer with raised parapet walls (e.g. along the sides of the dormer) that are higher than the main ridge-line. The previous versions of the "Technical Guidance" document implied that this would not be permitted development, on the basis the height of the extension would include any new parapet walls whereas the highest part of the existing roof would exclude any existing parapet walls. However, the above replacement of the word "should" with the word "may" raises the question of whether the "Technical Guidance" document still implies this interpretation in all situations, or only implies this interpretation in some situations.

As a result of the above amendment, the following conclusion within the "Highest part of the … roof" topic of the "GPDO Part 1 (All Classes) - LDC Appeal Decisions" document on this website has been updated to show that the "Technical Guidance" document no longer implies this interpretation in all situations:

For example, B.1(b) would not allow new raised parapet walls to be higher than the main ridge-line, even if the property has existing raised parapet walls that are higher than the main ridge-line.
[Source: Permitted development rights for householders - Technical Guidance].
[Note: This advice was added to the August 2010 version of the above document, but was subsequently amended in the April 2016 version to replace the phrase "should include any protrusions" with the phrase "may include any protrusions"].
[Note: The above document implies this conclusion (in at least some situations) by stating that "However, when calculating the height of the part of the house enlarged, this measurement should be at the highest part of the enlargement and may include any protrusions above the roof such as parapet walls etc."].

The restriction against front extensions (page 14):

Since the previous version of the "Technical Guidance" document was published in April 2014, limitation A.1(e) has been amended when the GPDO 1995 was replaced by the GPDO 2015 (link) on 15/04/2015. For info, the previous version of this limitation prevented a front extension only in those cases where "the principal elevation" fronts a highway, whereas the current version of this limitation prevents a front extension in all cases.

As such, on page 14 of the "Technical Guidance" document, in the section relating to limitation A.1(e), the previous advice has been replaced with the following:

"This restriction means that any development to enlarge a house that is in front of a principal elevation, or in front of a side elevation that fronts a highway will require an application for planning permission. Principal elevation has the meaning set out in the ‘General Issues’ section of this document (see page 7)."

As a result of the above amendment, the following conclusion has been added to the "A.1(e)" topic of the "GPDO Part 1 (All Classes) - LDC Appeal Decisions" document on this website:

For the purposes of the post-15/04/2015 version of A.1(e), where the principal elevation does not front a highway, an extension under Class A can not extend beyond a wall that forms the principal elevation.
[Source: Permitted development rights for householders - Technical Guidance].
[This advice is since April 2016].

The phrase "fronts a highway" (page 16):

On page 16 of the "Technical Guidance" document, in the section relating to limitation A.1(e), the previous advice about whether an elevation "fronts a highway" has been replaced with the following:

"The extent to which an elevation of a house fronts a highway will depend on factors such as:
(i) the angle between the elevation of the house and the highway. If that angle is more than 45 degrees, then the elevation will not normally be considered as fronting a highway;
(ii) the distance between the house and the highway - in cases where that distance is substantial, it is unlikely that a building can be said to front the highway. The same may be true where there is a significant intervening area of land in different ownership or use between the boundary of the curtilage of the house concerned and the highway."

For reference, for the situation where the angle between the elevation and the highway is more than 45 degrees, the previous advice stated that "the elevation will not be fronting a highway", whereas the above current advice states that "the elevation will not normally be considered as fronting a highway". In other words, the above amendment appears to indicate that it's possible (in at least some situations) for an elevation to front a highway even if the angle is more than 45 degrees.

For info, in the appeal decision "February 2016 - Code a00643", it was concluded that a particular elevation fronts the highway even though the angle is approx 55 degrees, whereas in the appeal decision "January 2010 - Code a00085" it was concluded that a particular elevation doesn't front the highway even though the angle is approx 45 degrees.

As a result of the above amendment, the following conclusion has been added to the "Fronts a highway" topic of the "GPDO Part 1 (All Classes) - LDC Appeal Decisions" document on this website:

If the angle between the elevation and the highway is more than 45 degrees, then the elevation will not normally “front” the highway.
[Source: Permitted development rights for householders - Technical Guidance].
[This advice is since April 2016].

The phrase "more than a single storey" (page 20):

On page 20 of the "Technical Guidance" document, in the section relating to limitation A.1(h), the previous advice has been replaced with the following:

"The enlarged part of the house (see page 7) could be a two storey extension to a house, or might comprise the addition of a storey onto a part of the house which has already been enlarged through permitted development - for example, the addition of a second storey onto an existing single storey extension. The entire enlarged part of the house must not extend beyond the rear wall by more than 3 metres for the development to qualify as permitted development."

For reference, the previous advice stated the following:

"The term “more than one storey” applies to the part of the house being enlarged through permitted development. This could either be a two storey extension to a house, or might comprise the addition of a storey onto an existing part of the house - for example, the addition of a second storey onto an existing single storey part of the house. The enlarged part of the house must not extend beyond the rear wall by more than three metres if it is to qualify as permitted development. Measurement of the extension beyond the rear wall should be made from the base of the rear wall of the original house that the enlargement extends beyond. Again, this limit applies to any rear wall being built out from (see diagrams under (e) above)."

In my opinion, it's difficult to assess the significance of the above amendment. It should be noted that the example in the above previous advice was "the addition of a second storey onto an existing single storey part of the house", whereas the example in the above current advice is "the addition of a second storey onto an existing single storey extension". It may be the case that the above amendment was made to indicate that the phrase "more than a single storey" does apply to (say) a proposed first floor extension on top of an existing non-original ground floor extension, but does not apply to (say) a proposed first floor extension on top of an original ground floor projection.

As a result of the above amendment, the following conclusion within the ""More than one storey" / "More than a single storey"" topic of the "GPDO Part 1 (All Classes) - LDC Appeal Decisions" document on this website has been updated to reflect the new wording of the above advice:

Where a proposed first floor extension would be on top of an existing (non-original) ground floor extension, then “the enlarged part of the dwellinghouse” does have “more than one storey” / “more than a single storey”.
[Source: Permitted development rights for householders - Technical Guidance].
[This advice is since April 2016].
[Note: The information on page 20 ("April 2016" version) of the above document refers to “the addition of a storey onto a part of the house which has already been enlarged through permitted development - for example, the addition of a second storey onto an existing single storey extension”, which could be interpreted as implying that the phrase “more than a single storey” only applies where the existing part of the house is non-original. Similarly, on page 21 ("April 2016" version), the example refers to where “a detached house has an existing, single storey, ground floor extension that was not part of the original house”, which could be interpreted as implying that the phrase “more than a single storey” only applies where the existing part of the house is non-original.].

The requirement for an extension with more than a single storey to be at least 7m from the rear boundary of the host property (page 21):

Since the previous version of the "Technical Guidance" document was published in April 2014, limitation A.1(h) has been amended by SI 2016 No. 332 (link) on 06/04/2016. For info, with the previous version of this limitation, it was not clear whether an extension with more than a single storey must be 1) at least 7m from the rear boundary of the host property, or 2) at least 7m from the boundary of the property to the rear, whereas with the current version of this limitation, it's clear that such an extension must be at least 7m from the rear boundary of the host property.

As such, on page 21 of the "Technical Guidance" document, in the section relating to limitation A.1(h), the previous advice has been replaced with the following:

"In addition, where the extension or enlarged part of the house has more than one storey, it must be a minimum of 7 metres away from any boundary of its curtilage which is opposite the rear wall of the house being enlarged."

In addition, the diagram on the above page has been amended to remove the property to the rear.

As a result of the above amendment, the following conclusion has been added to the "A.1(h)" topic of the "GPDO Part 1 (All Classes) - LDC Appeal Decisions" document on this website:

For the purposes of the post-06/04/2016 version of A.1(h), the phrase “any boundary of the curtilage of the dwellinghouse opposite the rear wall of the dwellinghouse” refers to the boundary of the rear boundary of the host property, rather than the boundary of the property to the rear. [Note: In other words, the term “opposite” within this phrase corresponds to the preceding term “boundary”, rather than the preceding term “dwellinghouse”].
[Source: Permitted development rights for householders - Technical Guidance].
[This advice is since April 2016].

The 3m eaves height limit for an extension within 2m of a boundary (page 22):

On page 22 of the "Technical Guidance" document, in the section relating to limitation A.1(i), the previous advice has been replaced with the following:

"Where any part of a proposed extension to a house is within 2 metres of the boundary of its curtilage, then the maximum height of the eaves that is allowed for the proposal (or, if adding to an existing extension, the whole enlarged part), is 3 metres."

For reference, the previous advice stated the following:

"Where any part of a proposed extension to a house is within two metres of the boundary of the land surrounding the property, then the maximum height of the eaves that is allowed for all parts of the proposal is three metres."

In my opinion, the meaning of the above previous advice and the above current advice is probably the same - i.e. that where part of an extension would be within 2m of a boundary, then the 3m eaves height limit of A.1(i) would apply to the entire extension. For example, the reference within the above current advice to "the whole enlarged part" supports this interpretation in the situation where a proposed extension would be attached to an existing extension. Similarly, on page 43, the equivalent advice relating to limitation E.1(e) supports the equivalent interpretation in relation to outbuildings. However, in my opinion, it's frustrating that the reference within the above previous advice to "all parts" has been removed, because this particular phrase helped to ensure that this advice was clear.

As a result of the above amendment, the following conclusion has been added to the "A.1(i)" topic of the "GPDO Part 1 (All Classes) - LDC Appeal Decisions" document on this website:

Where part of an extension would be within 2m of a boundary, the 3m eaves height limit of A.1(i) would apply to the entire extension (i.e. not only to that part of the extension that’s within 2m of the boundary).
[Source: Permitted development rights for householders - Technical Guidance].
[This advice is since April 2016].
[Note: The information on page 22 ("April 2016" version) of the above document states that “Where any part of a proposed extension to a house is within 2 metres of the boundary of its curtilage, then the maximum height of the eaves that is allowed for the proposal (or, if adding to an existing extension, the whole enlarged part), is 3 metres.”. In my opinion, this indirectly supports the above conclusion.].

uPVC windows (page 31):

On page 31, in the section relating to condition A.3(a), the previous advice has been replaced with the following:

"- it may be appropriate to replace existing windows with new uPVC double-glazed windows or include them in an extension even if there are no such windows in the existing house. What is important is that they give a similar visual appearance to those in the existing house, for example in terms of their overall shape, and the colour and size of the frames."

For reference, the previous advice stated the following:

"- it may be appropriate to include new PVC double glazed windows in an extension even if there are no such windows in the existing house. What is important is that they give a similar visual appearance to those in the existing house, for example in terms of their overall shape, and the colour and size of the frames."

It should be noted that the above previous advice referred to new uPVC windows within an extension, whereas the above current advice appears to refer to new uPVC windows within either the main house or an extension. However, in my opinion, the meaning of the above previous advice and the above current advice is effectively the same.

It should be noted that, by retaining the phrase "it may be appropriate ...", the above current advice still implies that the replacement of timber windows with UPVC windows is permitted development in some cases, but is not permitted development in other cases. In other words, the above current advice still doesn't give a definite answer to the simple question "is it permitted development (on a typical house) to replace timber windows with UPVC windows?".

As a result of the above amendment, the following conclusion within the "Materials" topic of the "GPDO Part 1 (All Classes) - LDC Appeal Decisions" document on this website has been updated to reflect the new wording of the above advice:

Class A - windows (of the main house or an extension):
- “it may be appropriate to replace existing windows with new uPVC double-glazed windows or include them in an extension even if there are no such windows in the existing house. What is important is that they give a similar visual appearance to those in the existing house, for example in terms of their overall shape, and the colour and size of the frames.”
[Source: Permitted development rights for householders - Technical Guidance].
[Note: This advice was added to the August 2010 version of the above document, albeit that the above text shown with a ~~strikethrough~~ was subsequently amended in April 2016].

Solid wall insulation (page 32):

On page 32 of the "Technical Guidance" document, in the section titled "Solid Wall Installation" [sic], the previous advice has been replaced with the following:

"The installation of solid wall insulation constitutes an improvement rather than an enlargement or extension to the house and is not caught by the provisions of (e), (f), (g), (h) and (j)."

For reference, the previous advice referred only to "the provisions of d(i) and d(ii)", rather than to "the provisions of (e), (f), (g), (h) and (j)". However, in my opinion, the meaning of the above previous advice and the above current advice is effectively the same. This is because, although the previous advice referred only to A.1(d) (i.e. the current A.1(e)), it implied that solid wall insulation should not be assessed against those limitations and conditions that apply only to "the enlarged part of the dwellinghouse" (i.e. the current A.1(e), A.1(f), A.1(g), A.1(h), A.1(i), A.1(j), A.2(b), A.2(c), and A.3(c)). Indeed, it should be noted that the list of limitations and conditions within the above current advice is still incomplete, because it doesn't refer to A.1(i), A.2(b), A.2(c), or A.3(c).

As a result of the above amendment, the following conclusion has been added to "The enlarged part of the dwellinghouse" topic of the "GPDO Part 1 (All Classes) - LDC Appeal Decisions" document on this website:

The installation of solid wall insulation constitutes an improvement rather than an enlargement or extension to the house and is not caught by the provisions of (e), (f), (g), (h) and (j). [Note: In other words, solid wall insulation should not be assessed against those limitations and conditions of Class A that apply only to "the enlarged part of the dwellinghouse"].
[Source: Permitted development rights for householders - Technical Guidance].
[This advice is since April 2016].

L-shaped rear dormers and the 20cm set-back from the eaves, etc (page 36):

On page 36 of the "Technical Guidance" document, in the section relating to condition B.2(b), the previous advice has been replaced with the following (note: I've highlighted the new parts in bold):

"The enlarged part of the roof must not extend beyond the outer face of any wall of the original house if it is to qualify as permitted development, unless it joins the original roof to the roof of a rear or side extension. An interpretative provision at paragraph B.4 of Class B clarifies that for these purposes any roof tiles, guttering, fascias, barge boards or other minor roof details which overhang the outer face of the wall should not to be considered part of the roof enlargement.

The enlarged part of the roof may join the original roof to the roof of a rear or side extension (generally referred to as an ‘L-shaped dormer’ on a main roof and ‘outrigger’ or ‘back addition’ roof), whether the part of the house being extended forms part of the original house or is an enlargement, or the shape or level of the pitch of the roofs are different in relation to each other."

In my opinion, the above additional text indicates that an L-shaped rear dormer (i.e. a roof extension that extends from the main rear roof onto the roof of a rear projection) constitutes "an enlargement which joins the original roof to the roof of a rear or side extension", and therefore would not be subject to any of the requirements of condition B.2(b). Furthermore, although above additional text is poorly written, it appears to indicate that this would be the case 1) regardless of whether the rear projection is original or non-original (e.g. an original outrigger or an existing rear extension), 2) regardless of whether the rear projection has a pitched roof or a flat roof (i.e. the above reference to "shape"), and 3) regardless of whether the ridge-line (or flat roof) of the rear projection is at a higher level or lower level than the eaves of the main rear roof (i.e. the above reference to "level").

However, in my opinion, the above additional text is questionable, because it does not appear to accord with the actual wording of condition B.2(b). After all, the above additional text indicates that an L-shaped rear dormer that extends from the main rear roof onto the roof of an original rear projection (i.e. an "outrigger") constitutes "an enlargement which joins the original roof to the roof of a rear or side extension" (i.e. the exception set out by B.2(b)(i) and B.2(b)(ii)). And yet, with regards to the latter phrase, if the L-shaped rear dormer is the "enlargement", and the main rear roof is the "original roof", then this implies that the original rear projection constitutes a "rear or side extension". I'm not aware of any other part of the GPDO, or any other part of the "Technical Guidance" document, in which part of the original house constitutes an "extension".

As a result of the above amendment, the following conclusions have been added to the "B.2(b)" topic of the "GPDO Part 1 (All Classes) - LDC Appeal Decisions" document on this website:

For the purposes of the post-06/04/2014 version(s) of Part 1 of the GPDO, where a property has an original rear projection with a side-facing pitched roof, part of which is lower than the main rear roof, then an “L”-shaped roof extension (or similar) that extends from the main rear roof onto the side roof of the original rear projection is permitted development. [Note: The roof extension, for part of its (rearmost) width, extends across the original rear eaves].
[Source: Permitted development rights for householders - Technical Guidance].
[This advice is since April 2016].
For the purposes of the post-06/04/2014 version(s) of Part 1 of the GPDO, where a property has an original rear projection with a side-facing pitched roof, all of which is lower than the main rear roof, then an “L”-shaped roof extension (or similar) that extends from the main rear roof onto the side roof of the original rear projection is permitted development. [Note: The roof extension, for all of its (rearmost) width, extends across the original rear eaves].
[Source: Permitted development rights for householders - Technical Guidance].
[This advice is since April 2016].
For the purposes of the post-06/04/2014 version(s) of Part 1 of the GPDO, where a property has an original rear projection with a flat roof, which is lower than the main rear roof, then an “L”-shaped roof extension (or similar) that extends from the main rear roof onto the flat roof of the original rear projection is permitted development. [Note: The roof extension, for all of its (rearmost) width, extends across the original rear eaves].
[Source: Permitted development rights for householders - Technical Guidance].
[This advice is since April 2016].

Note: As well as the above three conclusions relating to an original rear projection, the equivalent three conclusions relating to a non-original rear extension have also been added to the above document.

Buildings attached to the house are not permitted under Part 1 Class E (page 41):

On page 41 of the "Technical Guidance" document, in the section titled "Class E – buildings etc", the previous advice has been replaced with the following:

"Buildings which are attached to the house are not permitted under Class E (they would be subject to the rules in Class A)."

For reference, the previous advice stated the following:

"Buildings should not be attached to the house ..."

In my opinion, the meaning of the above previous advice and the above current advice is effectively the same - i.e. that structures that are attached to the main house should be assessed against Part 1 Class A, whereas structures that are separated from the main house should be assessed against Part 1 Class E. However, in my opinion, the above amendment helps to ensure that this advice is clear.

As a result of the above amendment, the following conclusion has been added to the "Interaction between Class A and Class E" topic of the "GPDO Part 1 (All Classes) - LDC Appeal Decisions" document on this website:

Buildings which are attached to the house are not permitted under Class E (they would be subject to the rules in Class A).
[Source: Permitted development rights for householders - Technical Guidance].
[This advice is since April 2016].

Other (insignificant) amendments:

This particular update to the "Technical Guidance" document includes a relatively large number of insignificant amendments, and therefore only some of these are listed below:

On page 1 (front cover), the title of the document has been changed from "Permitted development for householders - Technical Guidance" to "Permitted development rights for householders - Technical Guidance".
On page 2 (copyright page), the copyright information has been reintroduced (this was present in the "August 2010" and "January 2013" versions, but not present in the subsequent versions).
On page 3 ("Contents"), the list of contents is now more detailed.
On page 4 ("Introduction"), the previous links to information on the Planning Portal website have been replaced with links to information on the Planning Practice Guidance website. Furthermore, on this page, the previous references to Statutory Instruments (SIs) 1995/418, 2008/2362, 2013/1101, and 2014/564 have been replaced with references to SIs 2015/596 and 2016/332. Furthermore, on this page, the following new advice has been inserted:
- "Permitted development rights do not remove requirements for permissions or consents under other regimes such as the building regulations and the Party Wall Act.".
On pages 6-7 ("General issues"), the definitions of "Raised", "Terrace house", and "Principal elevation" have been moved to this section from subsequent sections of the document.
On page 8 ("The structure of the rules on permitted development"), the reference to Part 2 of the GPDO has been amended so that it now also refers to "exterior painting, charging points for electric vehicles and CCTVs", and the previous reference to Part 40 of the GPDO has been replaced with a reference to "Part 14" of the GPDO.
On page 18 (relating to A.1(g)) and page 40 ("Class D - porches"), the previous links to information on the Planning Portal website have been removed.
The final section ("Interpretation of Part 1") has been removed, because the information within this section has been moved to the "General issues" section.
On various pages, references to "30 May 2016" (i.e. the deadline for larger rear extensions) have been replaced with references to "30 May 2019".
On various pages, references to "article 1(5) land" have been replaced with references to "article 2(3) land".
On various pages, references to "more than one storey" have been replaced with references to "more than a single storey".
On various pages, references to "veranda" have been replaced with references to "verandah".
On various pages, references to "rooflights." have been replaced with references to "roof lights/windows".
On various pages, dimensions (e.g. "20 centimetres", "150 millimetres", etc) have been converted into metres (e.g. "0.2 metres", "0.15 metres", etc).

Additional notes:

All links on the Planning Jungle website to the "Technical Guidance" document have been updated to ensure that they link to the current version of the document (i.e. the "April 2016" version).

Comments by the Planning Jungle website:

In my opinion, this updated version of the "Technical Guidance" document is another missed opportunity by DCLG. Despite the fact that this is now the 7th version of the "Technical Guidance" document, it still doesn't resolve a number of significant ambiguities within the legislation that even government Inspectors are unable to interpret consistently. For example, 7 1/2 years after the legislation came into force (on 01/10/2008), it's still not possible to give a definite answer to the simple question "is it permitted development (on a typical house) to replace timber windows with UPVC windows?".
DCLG could have identified most of these ambiguities by talking to Inspectors (or by referring to the documents on this website), and then could have taken the opportunity to resolve them via this updated version of the "Technical Guidance" document. Instead, most of these ambiguities still remain.

The Planning Jungle website

Part 1 of the GPDO | Consolidated Versions of Legislation

IMPORTANT: DCLG has updated its “Permitted development rights for householders – Technical Guidance” document (April 2016) …