Industrial plant, machinery and hardstanding under Part 7

Industrial plant permitted development rights live in Part 7 of Schedule 2 to the General Permitted Development Order 2015, which covers non-domestic extensions and alterations including industrial buildings and warehouses. Between them the classes in that Part allow plant and machinery to be installed on industrial land, hard surfaces to be laid within the curtilage, and industrial or warehouse buildings to be extended, all within limits on height, floorspace and position and all subject to the land not being designated.

One caution before any of it is relied on. Part 7 has been amended repeatedly, class letters have moved, and the limits differ between the classes, so read the consolidated text of the Part on legislation.gov.uk for the date you are working to rather than a summary.

What the Part covers, class by class in substance

The useful way to hold Part 7 in your head is by subject matter rather than by letter.

• Extension or alteration of an industrial building or warehouse, subject to caps on additional floorspace and on height, a restriction on proximity to the curtilage boundary, and a requirement that the use remains an industrial or warehouse use.
• Provision, rearrangement or replacement of plant or machinery on land used for an industrial process, subject to a height limit.
• Laying of a hard surface within the curtilage of an industrial building or warehouse for a purpose incidental to the undertaking.
• Equivalent, and different, rights for shops, offices, schools and hospitals, which have their own classes and their own limits.

Three qualifications apply across the industrial classes. The land must already be in the relevant use, since none of these rights create a use. The rights do not apply, or apply in reduced form, on article 2(3) land, which covers conservation areas, National Parks, National Landscapes, the Broads and World Heritage Sites. And a condition on an existing planning permission can remove them, which on a modern industrial estate is common.

That last point deserves checking first. Estate-wide permissions frequently carry conditions requiring approval of external plant, restricting external storage, or removing Part 7 rights entirely, and the condition overrides the Order.

Height limits on external plant

The plant and machinery class permits installation up to a stated height, measured from ground level, with a lower limit where the land is within a specified distance of the curtilage boundary. Those figures are in the current text of the class and they are the first thing to check, because process plant frequently exceeds them.

Where the plant is on a roof, the measurement basis changes, and rooftop chillers and air handling units are the most common cause of an unintentional breach. Measure from the same datum the class specifies rather than from the roof surface.

Two practical habits:

1. Get the supplier's dimensioned drawing before ordering, including acoustic enclosures and any support steelwork, because the enclosure often adds the height that breaks the limit.
2. Record the ground level datum used, with a survey point, so that the position can be evidenced years later.

Where plant exceeds the limit, a planning application for the plant alone is usually straightforward, and the issues will be appearance, noise and any air quality or odour effect rather than the principle.

Development within the curtilage, and where the curtilage ends

Part 7 rights attach to the curtilage of the industrial building or warehouse, which is not the same as the site boundary or the leasehold demise. Yard areas used with the building are normally within it. A separate field behind the yard, fenced off and unused, probably is not.

Hard surfacing rights are limited to purposes incidental to the undertaking, which covers circulation, parking and loading. It does not cover laying a surface as the first step towards an external storage operation, because that operation may itself be a material change of use.

Surface water is the other half of the hard surfacing question. Laying a large impermeable area changes run-off, and while the Order does not impose a drainage condition on the industrial hard surface class, the discharge itself may need consent from the water company or the Environment Agency, and an existing permission's drainage condition may bite.

Noise from plant is a separate control

Permitted development status says nothing about whether the plant can be operated without complaint. Three separate controls apply.

Designing to a noise limit before installation is far less painful than responding to an abatement notice afterwards. Where residential receptors are within earshot, a short assessment to BS 4142 establishes the rating level against the background and shows what attenuation is needed, and a Noise Impact Assessment prepared at that stage also gives you the evidence if a complaint follows.

Acoustic enclosures, anti-vibration mounts, attenuators on intake and discharge, and siting away from the boundary are the usual answers. All of them cost less at specification stage.

Storage in the open air

This is where operators most often stray outside permitted development. Using an open yard for the storage of materials or finished goods can be a material change of use, depending on the scale, duration and whether it is ancillary to the building's use.

A pallet of finished goods awaiting collection is ancillary. A yard racked out and used as the primary storage operation, with vehicle movements to match, is a different use of the land and needs permission. Between those two poles the question is one of fact and degree, and the factors that matter are the proportion of the site used, the permanence of the arrangement, visibility from outside, and whether the activity has its own vehicle movements.

Where open storage is intended, apply for it. A permission with conditions on stacking height, position and hours is a manageable outcome, while an enforcement notice halting the operation is not. Our note on Part 6 Class B and small agricultural units covers the analogous problem of rights that permit a building but not the use it is put to.

Where an environmental permit is engaged

Certain industrial processes require a permit under the Environmental Permitting (England and Wales) Regulations 2016, issued by the Environment Agency or by the local authority depending on the process.

Planning and permitting are separate. A permit does not authorise development, and permission does not authorise emissions. What matters practically is that the two should be applied for in a coordinated way, because the permit application will describe the plant and the abatement in detail, and inconsistency between that description and the planning drawings is the kind of thing an objector finds.

Where the process is permitted, the planning authority should not duplicate the pollution control regime, and national policy expects it to assume the permitting regime will operate effectively. That is a helpful argument, and it is not a complete answer, because amenity effects such as noise, dust and visual impact remain planning matters.

Recording the installation date

Permitted development leaves no paper trail, which becomes a problem the day somebody asks whether the plant is lawful.

Keep, for each installation:

• Dated photographs from a fixed position, showing the plant in place.
• The supplier's invoice and dimensioned drawing.
• A site plan marking the position, with the height and the datum used.
• A short note recording which class of Part 7 was relied on and the text of that class as it stood on the date.

Time limits for immunity from enforcement apply to operational development and have historically been four years, with the Levelling-up and Regeneration Act 2023 providing for a move to ten, so check the current position for the date of the works. Where the position is arguable, a certificate of lawfulness under section 191 of the Town and Country Planning Act 1990 settles it, and a Planning Statement setting out the history is the core of that application.

To see which supporting documents an industrial application is likely to need, browse the planning report types by category.

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