Part 7 extensions to shops, offices and industrial units

Part 7 of Schedule 2 to the General Permitted Development Order 2015 grants a commercial extension permitted development right, and it is narrower than most occupiers hope. Each building type gets its own class with its own floorspace cap, height cap and boundary distance, and the cap is almost always expressed against the original building rather than the building as it stands today. Get the baseline wrong and the extension you thought was permitted is unauthorised development from the day it is built.

The tests below are the ones to run, in order, before anyone draws a plan.

Which buildings Part 7 covers

Part 7 is titled non-domestic extensions, alterations etc, and it is arranged by building type rather than by activity. Separate classes deal with shops and financial or professional services establishments, with schools, colleges, universities and hospitals, with office buildings, and with industrial buildings and warehouses. Each extension class is paired with a hard surface class for the curtilage, and the industrial group adds classes for plant, machinery and development needed for an industrial process.

The class letters have been amended since 2015, so quote the class by its heading and read the current consolidated text on legislation.gov.uk rather than trusting a letter copied from an older note. Reading a class properly means reading four things together: what it permits, the list of cases where development is not permitted, the conditions attached, and the interpretation paragraph at the end of the Part. Our guide to reading the GPDO without getting lost sets out that sequence.

What Part 7 never does is change the use. An extension to a warehouse is still a warehouse. If you want more floorspace and a different activity, Part 7 gets you the floorspace and Part 3 or a full application gets you the use, and the two have to be sequenced so that the building is in the right use at the moment each right is exercised.

The tests every Part 7 class applies

Article 2(1) of the Order defines original in the way that catches people out. A building is original as it existed on 1 July 1948 or, if built after that date, as it was built. Every extension since then eats into the allowance, whether or not it was built under permitted development and whether or not the current owner built it. On an industrial estate where units have been extended twice, the allowance is often already spent.

Article 2(3) land means land in a conservation area, a National Park, the Broads, an area of outstanding natural beauty, or a World Heritage Site. Several Part 7 classes are simply switched off on that land, and others reduce what they allow.

Where the site adjoins housing

The boundary tests are the reason most small commercial extensions fail. A class will typically allow an extension close to a boundary in general terms and then impose a greater separation where the boundary adjoins land in residential use, which in practice means the back fence of the houses behind the unit.

Two further points follow. Permitted development does not carry an amenity judgement, so there is no officer weighing overlooking against need, which means the distances are absolute and an extension a few hundred millimetres inside the line is not permitted at all. And the conditions attached to these classes usually require the materials used in the exterior work to be similar in appearance to those of the exterior of the existing building, which rules out the lowest cost cladding option on a brick building.

Where the numbers do not work, the answer is a full planning application. That is not a defeat. A short Planning Statement that sets the extension against the development plan's employment policies, plus a drawn section showing the relationship to the gardens behind, gets a modest extension through delegated powers in most authorities.

Car parking, hard surfacing and plant

The hard surface classes in Part 7 allow a hard surface within the curtilage of the relevant building for a purpose incidental to the undertaking, and they are conditioned on surface water drainage. On any site of consequence that condition is the whole story, because laying impermeable surfacing that discharges to the highway is not what the class permits. A permeable build-up, or a positive drainage system discharging to a soakaway or an attenuated outfall, is what makes the right usable.

Plant and machinery on industrial land has its own class with a height limit and its own designated land exclusions. Replacing a chiller like for like is usually straightforward. Adding an extraction stack that rises above the roofline rarely is.

Rights that have already been removed

Three things switch Part 7 off before you start.

1. A condition on an earlier planning permission. Article 3(4) of the Order means permitted development cannot authorise anything that would breach a condition imposed on a grant of permission, and estate permissions from the 1980s and 1990s frequently condition the total floorspace or remove extension rights outright.
2. An Article 4 direction made by the local planning authority.
3. A listed building or a scheduled monument, where consent is needed for the works regardless of what the Order says. The position on outbuildings and yards is set out in our note on permitted development rights in a listed building curtilage.

There is also the general restriction in article 3 on development that would involve forming, laying out or materially widening an access to a trunk or classified road. A new service entrance for a loading bay can trip it.

Confirming the lawful use before you rely on the right

Part 7 classes attach to a building in a particular use. An extension class for a shop does nothing for a building whose lawful use is storage, even if a shop has traded from it for two years.

So establish the lawful use first, from the planning history, the permission conditions, and where necessary the evidence of what has actually happened on the ground. Where the use arose through the passage of time rather than a grant of permission, the only way to put it beyond argument is a certificate of lawfulness of existing use or development under section 191 of the Town and Country Planning Act 1990, or a certificate for a proposed use under section 192. The fee is lower than a full application, the authority has eight weeks, and the certificate binds the authority on the facts it records.

Occupiers often resist that step because it costs money and time on a building they already own. The counter-argument is that a lender, a purchaser or an incoming tenant will ask the same question later, and answering it once costs less than answering it under pressure.

What Part 7 does not exempt you from

Building regulations apply to the extension in the ordinary way, including Part B fire safety and Part L. A Community Infrastructure Levy charge can arise on permitted development, and the notice requirements bite whether or not there is a planning application to hang them on, which our piece on permitted development and the Community Infrastructure Levy covers. Where the building is in a flood zone, the Environment Agency's position on the extension still matters even without an application to comment on.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it, and treat a Lawful Development Certificate as the only formal confirmation that works are lawful.

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