Data centres: which use class applies
Classifying a data centre is a matter of fact and degree, and the answer rarely decides the scheme. Grid capacity and plant noise do.
A data centre use class is not fixed by the Town and Country Planning (Use Classes) Order 1987, which does not name the use at all. Three readings are argued in practice: Class B8 storage or distribution, on the basis that the building stores something; Class B2 general industrial, on the basis that an industrial process is carried on; and no class at all, with the use treated as sui generis. The classification is a matter of fact and degree for the local planning authority, and on a new-build application it usually matters far less than applicants expect.
What decides these applications is grid capacity, plant noise and water. The use class argument only matters when you are converting an existing building and hoping to avoid an application.
How data centres have been classified in practice
The B8 argument reads "storage" literally. Data is stored, so the building is a storage use. The weakness is that the storage classes were drafted around goods and materials moving in and out, and a data centre has almost no goods movement once fitted out.
The B2 argument focuses on the plant. Transformers, uninterruptible power supplies, chillers and generators make the building closer to a process plant than a warehouse, and B2 is the class for industrial processes that are not light industry.
The sui generis argument says the use fits neither description, and that treating it as outside the classes is the honest answer. It has the practical advantage of removing any argument about what the building could change into later, which is sometimes what an authority wants.
Class E(g) is occasionally raised and rarely survives. Class E(g)(iii) light industry is limited to processes that can be carried out in any residential area without detriment to amenity, and a building with external chillers and standby diesel generators does not meet that test.
Where the answer matters commercially, apply for a Lawful Development Certificate under section 192 of the Town and Country Planning Act 1990 for the proposed use. That is the only formal confirmation, and on a conversion of an existing industrial building the fee is small against the cost of getting it wrong.
| Reading | Argument | Main weakness |
|---|---|---|
| Class B8 | Data is stored on the premises | Storage classes are framed around goods movement |
| Class B2 | Power and cooling plant make it a process building | Not obviously a manufacturing or treatment process |
| Class E(g)(iii) | Light industry with no process emissions | Fails the residential area amenity test |
| Sui generis | Fits no class as drafted | No fallback use, so any change needs permission |
One honest uncertainty: I have seen the same building type classified differently by neighbouring authorities, and there is no settled answer to quote. Ask early and get it in writing.
Grid connection and the capacity constraint
Planning permission does not deliver electricity. On a large data centre the connection is the long pole in the programme, and it runs on a timetable the planning system has no influence over.
Three things to establish before you commit to a site. What capacity is available at the nearest point of connection, what the connection offer timescale is, and whether reinforcement works are needed that themselves require consent. Reinforcement can mean new cable routes, a substation and sometimes an overhead line, each with its own planning or statutory authorisation.
Put the connection position in the application honestly. An authority asked to grant permission for a 50 megawatt load will ask how it is to be supplied, and an answer that defers the question invites a condition tying implementation to evidence of a connection agreement.
On-site generation, battery storage and heat export all change the picture and all add plant. A utilities assessment setting out electricity, water and telecoms capacity and the route to securing each is what a well-prepared application includes.
Government has signalled an intention to change how large data centres are consented, including through the nationally significant infrastructure route. As at October 2026, treat that as announced rather than settled and check the current position before assuming which regime applies.
Plant noise and the nearest receptor
Noise is the issue that most often shapes the building. Chillers, dry coolers, fans and transformers run continuously, and standby generators are tested periodically.
Assessment follows BS 4142:2014+A1:2019, comparing a rating level against the background sound level at the nearest noise sensitive receptor. Three features of data centre plant make it harder than a typical commercial scheme.
It runs at night, when background levels are at their lowest, so the assessment is driven by the 23:00 to 07:00 period rather than by daytime conditions.
It is tonal and sometimes low frequency, which attracts character corrections that add to the rating level. A fan array at blade passing frequency is audible well beyond the point where a broadband assessment would suggest it is not.
It is cumulative. A site with forty dry coolers is not one source assessed forty times, and the combined sound power has to be modelled with the building's own screening taken into account.
A noise impact assessment with measured background levels, manufacturer sound power data by octave band and a model of the final layout is the minimum. Councils usually expect a suitably qualified author for this work and professional review is strongly advised. Design the acoustic strategy before the plant layout is fixed, because moving a cooler bank after the structural grid is set is expensive.
Water for cooling
Evaporative and adiabatic cooling systems use water, and the quantity can be material in a catchment under stress.
Ask the water undertaker early about supply capacity and about the discharge of blowdown to sewer, which may need a trade effluent consent. In a water neutrality area the demand has to be offset, and that is a scheme-level constraint rather than a detail.
And closed-loop or air-cooled systems avoid the water question entirely, at the price of efficiency. That is an engineering trade-off rather than a planning one, but it is the sort of trade-off an authority in a stressed catchment will push you towards. Where the design uses water, state the annual and peak demand in the application, because an authority that has to guess will consult the undertaker and wait for the answer.
Backup generation and air quality
Standby generators are usually diesel, and that brings two regimes into play.
Environmental permitting applies to specified generators and medium combustion plant, with thresholds based on rated thermal input and operating hours, so the permit position depends on the size of the plant and how it is used. Establish whether a permit is needed and who is applying for it.
For planning, the issues are the emissions during testing and the stack height. An air quality assessment modelling nitrogen dioxide concentrations at nearby receptors during testing, with the stack height optimised, is what the environmental health officer will expect, particularly inside an air quality management area.
Testing is also a noise question, and the two assessments should use the same testing regime assumption. Nothing undermines an application faster than a noise report assuming monthly daytime testing and an air quality report assuming weekly.
Conditions to expect
Four conditions appear on almost every permission.
A noise limit expressed as a rating level at a defined receptor, to be demonstrated by post-completion measurement rather than by prediction alone.
Restrictions on generator testing: days, hours and frequency. These are negotiable before the decision and hard to change afterwards, so ask for what the operation actually needs. Our note on varying an opening hours condition shows what the section 73 route involves if you get it wrong.
Approval of external plant details, including any enclosure or acoustic screening, before installation.
A requirement for evidence of the grid connection, or of water supply capacity, before development starts or before occupation.
Browse all 66 PlanScope report types and start a draft, including the planning statement that sets out the use class position and the policy case.
This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.
Frequently asked questions
Does the Use Classes Order mention data centres?
No. The Order does not name the use, so classification is a matter of fact and degree for the local planning authority. Arguments are run for Class B8 storage, Class B2 general industrial and for the use falling outside every class. Where the answer matters, apply for a Lawful Development Certificate.
Can I convert a warehouse to a data centre without permission?
Only if the authority accepts that the use remains within the same class, which turns on the facts of the particular building and operation. External plant will usually need permission in its own right regardless. Get a written view from the authority, or a Lawful Development Certificate under section 192, before committing.
Is a data centre light industry under Class E(g)?
Almost never. Class E(g)(iii) covers light industry capable of being carried out in any residential area without detriment to amenity. External chillers, transformers and standby diesel generators do not satisfy that test, so the argument rarely survives scrutiny by an environmental health officer.
What makes data centre noise assessment different?
It runs continuously, so the night-time period with the lowest background levels governs. The plant is often tonal or low frequency, which attracts character corrections that increase the rating level. And many identical units combine, so the assessment has to model combined sound power with building screening rather than assess a single source.
Does planning permission secure the electricity connection?
No. The connection is a separate commercial and regulatory process with its own timetable, and reinforcement works may need their own consents. Establish available capacity, the offer timescale and any reinforcement requirement before committing to a site, and expect a condition requiring evidence of the connection agreement.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.