Government changes offer flexibility when extending commercial premises


The Government’s efforts to free up and simplify the planning system have included some significant rights to extend commercial premises, through Part 7 of the General Permitted Development Order, which was revised in 2015, writes FBCMB's Niall Blackie.

This note covers offices (B1(a) uses) and commercial premises (B1(c) (light industrial), B2 (general industrial) and B8 (storage and distribution). In this context, these use descriptions refer to the primary use of buildings, not to open land, and not to buildings that are in an ancillary use (so for example, a storage unit to a shop is not a B8 use at all). 

It is important to note that conditions on a Planning Permission, or Directions under Article 4 of the Order may (in special situations) take away the right to rely on the Order, and that the permissions given do not override other controls such as the listed building regime, or s106 obligations or restrictive covenants. Some of the rights are different on ‘article 2(3) land’: this is land which is in a conservation area, World Heritage Site, National Park, or AONB, or Wildlife area under the 1981 Act, or in the Broads.

All of the rights refer to the term ‘curtilage’. The extent of the curtilage of a building is a matter of complex legal interpretation – it is not simply the land within a single ownership, nor is it synonymous with the ‘planning unit’, and when used in the planning regime it is not necessarily the same area as is referred to in a conveyancing context. 

The Order allows development which is completely within the constraints noted. If any part of the development is beyond those constraints, the whole development is unlawful, and could be enforced against. Care is needed to avoid that risk!

Offices: Class F allows the extension of the gross floorspace of a B1(a) office building by up to the lesser of 50% or 100m2; or, if the building is on article 2(3) land or on a SSSI, by up to the lesser of 25% or 50m2. When calculating this area, one must treat two buildings within a single curtilage as a single ‘original’ building. 

* The right is not available at all if the building is in the curtilage of a listed building. 
* The materials used must match the existing if the building is on article 2(3) land. 
* No part of the extension may be within 5m of the curtilage boundary.  

There is a height constraint of 5m if any part of the extended building would be within 10m of the boundary of the curtilage of the building, but otherwise the building must not exceed the height of the building being extended. Class F also allows an existing B1(a) office to be altered, but only at ground floor level, and so long as it is not on article 2(3) land, and not in the curtilage of a listed building.

Once altered or extended the building may only be used for the same purposes as the existing office, Class G allows hard surfaces to be created or replaced, to serve an office and the cumulative maximum area that can be created in this way is 50m2, although the calculation of this area excludes any area that existed prior to 6 April 2010. 

This right does not apply to any land in the curtilage of a listed building. 

There are important drainage conditions attached to this right: if there is ‘a risk of groundwater contamination’ then the area must not be porous; but in other areas, the surface must either be porous or run off into a porous/permeable area. The assessment of the risk level is not the subject of any guidance!

Industrial Buildings (B1(c) or B2)  or Warehouse (B8): Class H deals with these. It allows the extension or alteration of such buildings, (provided that the building in question was not itself built under Class H) and in addition permits the erection of new buildings; but in all cases the right is limited to land within the curtilage of an existing building in such use. (Interestingly the term warehouse is defined by reference to ‘any building within Class B8’, and of course Class B8 has not been limited to warehouses for many years now.)

There is a user restriction: such buildings can only be used for the purposes of the existing undertaking; this can be for employee (social care or recreation) facilities; but in addition in the case of an industrial building, the use could be for an industrial process or for R&D of products or process, and in the case of warehousing, the use could be for storage and distribution. But the user restriction means that the right cannot be relied on for example to build an office extension for such premises. There are limitations on use outside certain hours of operation for people from outside the undertaking – so if one built a staff canteen, it cannot be used as a café for all and sundry, not even at night time. 

There are limitations on the amount of hazardous substances that can be held. The Class H rights have several limitations. None of the development can lie within 5m of the boundary of the curtilage of the building, or be within the curtilage of a listed building. Importantly, too, the work must not lead to a reduction in the space available for parking or turning vehicles.

For new buildings, on article 2(3) land or on a SSSI, the maximum gross floorspace of a new  building is 100 m2, but elsewhere it is 200 m2. The height of a new building must not be more than 5m if any part of the building is within 10m of the boundary of the curtilage; but otherwise it must be no higher than the height of the highest building on the curtilage, or 15m, if that is less.  

For extensions, the floorspace limit for article 2(3) land is the lesser of 500 m2 or 10%; on SSSI land the limit is the lesser of 1,000 m2 or 25%; on all other land the limit is the lesser of 1,000 m2 or 50%. The height of an extension or altered building must be no more than 5m if any part of the building is within 10m of the boundary of the curtilage; and in other cases, no more than the height of the building being extended or altered.

* In cases on article 2(3) land the materials must be similar to those on the existing.
* These rights are very different from the old industrial building permitted development rights

Class I replicates the old permission for plant and machinery and apparatus. Class J allows a hard standing to be created or replaced but not in the curtilage of a listed building

Our Planning Team can advise on the availability of these rights in your particular context, and can carry out the research necessary to see whether they would apply to your land, or are restricted; we can advise on the concept of curtilage; and can explain how to secure a certificate of lawfulness to deal with any doubt as to the availability of the rights, so as to avoid unnecessary risks to your land and building investments.

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