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Class A – enlargement, improvement or other alteration of a dwellinghouse

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What is allowed?
  • Single-Storey rear extension
  • Single Storey side extension
  • Two Storey rear extension
What are the limits – Single-storey rear extension

Development is not permitted by Class A if—
a) permission to use the dwellinghouse as a dwellinghouse has been granted only by virtue of Class M, N, P, PA or Q of Part 3 of this Schedule (changes of use);
b) as a result of the works, the total area of ground covered by buildings within the curtilage of the dwellinghouse (other than the original dwellinghouse) would exceed 50% of the total area of the curtilage (excluding the ground area of the original dwellinghouse);
c) the height of the part of the dwellinghouse enlarged, improved or altered would exceed the height of the highest part of the roof of the existing dwellinghouse;
d) the height of the eaves of the part of the dwellinghouse enlarged, improved or altered would exceed the height of the eaves of the existing dwellinghouse;
e) the enlarged part of the dwellinghouse would extend beyond a wall which—
(i) forms the principal elevation of the original dwellinghouse; or
(ii) fronts a highway and forms a side elevation of the original dwellinghouse;
f) subject to paragraph (g), the enlarged part of the dwellinghouse would have a single storey and—
(i) extend beyond the rear wall of the original dwellinghouse by more than 4 metres in the case of a detached dwellinghouse, or 3 metres in the case of any other dwellinghouse, or
(ii) exceed 4 metres in height;
g) for a dwellinghouse not on article 2(3) land nor on a site of special scientific interest, the enlarged part of the dwellinghouse would have a single storey and—
(i) extend beyond the rear wall of the original dwellinghouse by more than 8 metres in the case of a detached dwellinghouse, or 6 metres in the case of any other dwellinghouse, or
(ii) exceed 4 metres in height;
i) the enlarged part of the dwellinghouse would be within 2 metres of the boundary of the curtilage of the dwellinghouse, and the height of the eaves of the enlarged part would exceed 3 metres;
ja) any total enlargement (being the enlarged part together with any existing enlargement of the original dwellinghouse to which it will be joined) exceeds or would exceed the limits set out in sub-paragraphs (e) to (j);
k) it would consist of or include—
(i) the construction or provision of a verandah, balcony or raised platform,
(ii) the installation, alteration or replacement of a microwave antenna,
(iii) the installation, alteration or replacement of a chimney, flue or soil and vent pipe, or
(iv) an alteration to any part of the roof of the dwellinghouse.; or
l) the dwellinghouse is built under Part 20 of this Schedule (construction of new dwellinghouses).

What are the limits – Single-storey side extension

Development is not permitted by Class A if—
a) permission to use the dwellinghouse as a dwellinghouse has been granted only by virtue of Class M, N, P, PA or Q of Part 3 of this Schedule (changes of use);
b) as a result of the works, the total area of ground covered by buildings within the curtilage of the dwellinghouse (other than the original dwellinghouse) would exceed 50% of the total area of the curtilage (excluding the ground area of the original dwellinghouse);
c) the height of the part of the dwellinghouse enlarged, improved or altered would exceed the height of the highest part of the roof of the existing dwellinghouse;
d) the height of the eaves of the part of the dwellinghouse enlarged, improved or altered would exceed the height of the eaves of the existing dwellinghouse;
e) the enlarged part of the dwellinghouse would extend beyond a wall which—
(i) forms the principal elevation of the original dwellinghouse; or
(ii) fronts a highway and forms a side elevation of the original dwellinghouse;
f) subject to paragraph (g), the enlarged part of the dwellinghouse would have a single storey and—
(i) extend beyond the rear wall of the original dwellinghouse by more than 4 metres in the case of a detached dwellinghouse, or 3 metres in the case of any other dwellinghouse, or
(ii) exceed 4 metres in height;
g) for a dwellinghouse not on article 2(3) land nor on a site of special scientific interest, the enlarged part of the dwellinghouse would have a single storey and—
(i) extend beyond the rear wall of the original dwellinghouse by more than 8 metres in the case of a detached dwellinghouse, or 6 metres in the case of any other dwellinghouse, or
(ii) exceed 4 metres in height;
i) the enlarged part of the dwellinghouse would be within 2 metres of the boundary of the curtilage of the dwellinghouse, and the height of the eaves of the enlarged part would exceed 3 metres;
j) the enlarged part of the dwellinghouse would extend beyond a wall forming a side elevation of the original dwellinghouse, and would—
(i) exceed 4 metres in height,
(ii) have more than a single storey, or
(iii) have a width greater than half the width of the original dwellinghouse;
ja) any total enlargement (being the enlarged part together with any existing enlargement of the original dwellinghouse to which it will be joined) exceeds or would exceed the limits set out in sub-paragraphs (e) to (j);
k) it would consist of or include—
(i) the construction or provision of a verandah, balcony or raised platform,
(ii) the installation, alteration or replacement of a microwave antenna,
(iii) the installation, alteration or replacement of a chimney, flue or soil and vent pipe, or
(iv) an alteration to any part of the roof of the dwellinghouse.; or
l) the dwellinghouse is built under Part 20 of this Schedule (construction of new dwellinghouses).

What are the limits – two-storey rear extension

Development is not permitted by Class A if—
a) permission to use the dwellinghouse as a dwellinghouse has been granted only by virtue of Class M, N, P, PA or Q of Part 3 of this Schedule (changes of use);
b) as a result of the works, the total area of ground covered by buildings within the curtilage of the dwellinghouse (other than the original dwellinghouse) would exceed 50% of the total area of the curtilage (excluding the ground area of the original dwellinghouse);
c) the height of the part of the dwellinghouse enlarged, improved or altered would exceed the height of the highest part of the roof of the existing dwellinghouse;
d) the height of the eaves of the part of the dwellinghouse enlarged, improved or altered would exceed the height of the eaves of the existing dwellinghouse;
e) the enlarged part of the dwellinghouse would extend beyond a wall which—
(i) forms the principal elevation of the original dwellinghouse; or
(ii) fronts a highway and forms a side elevation of the original dwellinghouse;
(i) extend beyond the rear wall of the original dwellinghouse by more than 3 metres, or
(ii) be within 7 metres of any boundary of the curtilage of the dwellinghouse being enlarged which is opposite the rear wall of that dwellinghouse;
i) the enlarged part of the dwellinghouse would be within 2 metres of the boundary of the curtilage of the dwellinghouse, and the height of the eaves of the enlarged part would exceed 3 metres;
ja) any total enlargement (being the enlarged part together with any existing enlargement of the original dwellinghouse to which it will be joined) exceeds or would exceed the limits set out in sub-paragraphs (e) to (j);
k) it would consist of or include—
(i) the construction or provision of a verandah, balcony or raised platform,
(ii) the installation, alteration or replacement of a microwave antenna,
(iii) the installation, alteration or replacement of a chimney, flue or soil and vent pipe, or
(iv) an alteration to any part of the roof of the dwellinghouse.; or
l) the dwellinghouse is built under Part 20 of this Schedule (construction of new dwellinghouses).

A.2. In the case of a dwellinghouse on article 2(3) land, development is not permitted by Class A if—
(a) it would consist of or include the cladding of any part of the exterior of the dwellinghouse with stone, artificial stone, pebble dash, render, timber, plastic or tiles;
(b) the enlarged part of the dwellinghouse would extend beyond a wall forming a side elevation of the original dwellinghouse; or
(c) the enlarged part of the dwellinghouse would have more than a single storey and extend beyond the rear wall of the original dwellinghouse.
(d) any total enlargement (being the enlarged part together with any existing enlargement of the original dwellinghouse to which it will be joined) exceeds or would exceed the limits set out in sub-paragraphs (b) and (c).

Conditions

A.3 Development is permitted by Class A subject to the following conditions
(a) the materials used in any exterior work (other than materials used in the construction of a conservatory) must be of a similar appearance to those used in the construction of the exterior of the existing dwellinghouse;
(b) any upper-floor window located in a wall or roof slope forming a side elevation of the dwellinghouse must be—
(i) obscure-glazed, and
(ii) non-opening unless the parts of the window which can be opened are more than 1.7 metres above the floor of the room in which the window is installed; and (c) where the enlarged part of the dwelling-house has more than a single storey, or forms an existing enlargement of the original dwellinghouse the roof pitch of the enlarged part must, so far as practicable, be the same as the roof pitch of the original dwellinghouse.4—(1) The following conditions apply to development permitted by Class A which exceeds the limits in paragraph A.1(f) but is allowed by paragraph A.1(g).

Our Views on Class A

Class A Development is the cornerstone of householder Permitted Development providing the basis for many extensions and other alterations to houses in England.

Class A is available to buildings that are within Conservation Areas (subject to Local Article 4 Directions ) and to smaller HMO’s so long as they remain a single dwelling house. This allowance is not available to Listed Buildings.

With the exception of the larger extensions above 4m in depth no application is required for a Class A extension. It is often best practice however to seek a certificate of lawful development in order to ensure that your proposals comply in full. This is especially important where Council’s have sought to resist development to houses such as larger extensions.

Class A is immune from the imposition of the National Floor-space Standards as the development does not result in a new dwelling.

The ‘existing dwelling’ provision is set in law as the day the property was constructed or the 1st July 1948 (whichever the sooner).

How to Use Class A

Class A permitted development should be explored first before engaging with a planning permission and as with other permitted development allowances it is best practice to seek a lawful development certificate or prior approval where one is required.

*Correct at time of writing.

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