Material change of use: the test and the evidence
Section 55 gives no threshold for materiality. The method is to fix the planning unit, describe the character of each use and ask whether the difference matters in planning terms.
The material change of use test is a question of fact and degree, decided by comparing the character of the use before and after. Section 55(1) of the Town and Country Planning Act 1990 defines development as including the making of any material change in the use of any buildings or other land, and it offers no threshold, no percentage and no list. What the courts have supplied instead is a method: identify the planning unit, describe the character of the existing lawful use, describe the character of the proposed use, and ask whether the difference is material in planning terms.
Nothing in that method asks which use class each use falls into. That is a separate question, and conflating the two is where most arguments start.
Change of use within section 55
Section 55 does two things. It defines development, and it then carves out a list of things that are not development.
Four of those exclusions matter in everyday practice. Works affecting only the interior of a building, or not materially affecting its external appearance, are not development. The use of any building or land within the curtilage of a dwellinghouse for a purpose incidental to the enjoyment of the dwellinghouse is not development. The use of land for agriculture or forestry is not development. And a change of use within the same class of the Use Classes Order is not development.
Section 55(3) then adds two deemed cases. The use of a building previously used as a single dwellinghouse as two or more separate dwellinghouses involves a material change of use, of the building and of each part of it. That provision is why a house-to-flats conversion always needs permission regardless of how little changes physically.
So the analysis runs in order. Is there a change of use at all. If so, is it taken outside development by section 55(2) or deemed to be development by section 55(3). If neither, is the change material.
What makes a change material rather than trivial
Materiality is judged on the character of the use, not on its intensity alone and not on the label the occupier uses.
The courts have consistently framed the question as whether the character of the use has changed, and the comparison is between the lawful existing use at the intensity it was lawfully carried on and the proposed use. That phrasing matters. A vacant shop is still lawfully a shop, so the comparison is against a trading shop rather than against an empty unit.
Factors that bear on character include the activities carried on, the hours, the number of people attending, the vehicle movements generated, the nature of any process, whether goods are sold or made, and the effect on the locality. No single factor decides it, and a change can be material on one factor alone where that factor defines the use.
Two things do not make a change material. A change of occupier makes no difference, since planning controls the use of land rather than who carries it on. And a change of trading name or business model is irrelevant unless it alters what actually happens on the site.
Identifying the planning unit
Before anything is compared, the unit being compared has to be settled, and the authority for that remains the approach set out in Burdle.
Three situations are distinguished. Where the whole of a unit of occupation is used for a single main purpose, with other activities ancillary to it, the whole unit is the planning unit. Where within a single unit of occupation there are two or more physically separate and distinct areas occupied for substantially different purposes, each area is a separate planning unit. And where within a single unit there are physically distinct areas each used for a substantially different purpose, those areas may be separate units even without separate occupation.
The practical consequence is large. Introducing a 40 m² takeaway counter into a 900 m² supermarket is unlikely to change the character of the supermarket's use. Putting the same counter into a 60 m² shop changes the character of the whole unit. Same activity, different planning unit, different answer.
Get the unit wrong and everything downstream is wrong, including the floor area percentages people are fond of quoting.
Intensification and when it becomes a change
Intensification of an existing use can amount to a material change of use, but only where the intensification alters the character of the use rather than merely its volume.
The distinction is easier to state than to apply. A guest house taking more bookings is still a guest house. A guest house converting to short-let serviced accommodation with weekly turnover, key safes and no on-site management may have changed character even though the physical activity looks similar. A haulage yard moving from three vehicles to thirty has probably changed the character of the use of the land, and the planning judgement will focus on the vehicle movements and the hours rather than on the count itself.
Three evidential questions decide intensification cases. What was the lawful level of activity, and how is that established. What is the current or proposed level, measured rather than described. And which characteristic of the use has changed as a result, expressed as something an officer can assess.
Where an authority alleges intensification amounting to a breach, the burden is on the authority to establish the breach, which is the reverse of the position on a certificate application.
Ancillary activity growing into a primary use
An activity that starts as ancillary to a main use can become a primary use in its own right, and when it does, a material change of use has occurred without anybody making a decision.
The farm shop is the standard illustration. Selling the holding's own produce from a shed is ancillary to agriculture. Selling mostly bought-in goods from a converted barn with a car park and a cafe is retail, and the transition happens gradually. The same pattern appears in a workshop that becomes a trade counter, a pub that becomes a restaurant, and a garage that becomes a vehicle sales business.
Within a dwellinghouse the test is different again. Section 55(2)(d) excludes uses incidental to the enjoyment of the dwellinghouse, and whether a use is incidental is judged objectively rather than by the occupier's own view of their hobby. Breeding dogs commercially in a domestic garden has been held to fall outside the exclusion, and running a business employing staff from a house generally does too.
Where a condition restricts the use of a building, the condition can bite before materiality does. Those conditions still have to meet the usual tests, set out in our note on the six tests a planning condition has to meet.
Evidence of the lawful existing use
Everything compares against the lawful use, so establishing it is the first piece of work rather than the last.
| Source | What it establishes |
|---|---|
| Planning history, including permissions and conditions | The permitted use and any restriction on it |
| An existing certificate under section 191 | A conclusive statement of lawfulness for what it describes |
| Council tax and rating records | Occupation and the described use over time |
| Tenancy agreements, accounts and utility records | Continuity of use and its scale |
| Historic aerial and street-level imagery, historic mapping | Physical arrangement at dated points |
| Statutory declarations from occupiers and agents | Activity and dates, where documents are missing |
Two complications recur. A use carried on in breach of control for long enough becomes immune from enforcement, and the immunity period has been extended by the Levelling-up and Regeneration Act 2023, subject to the date it came into force and the transitional provisions. And a use can be abandoned, which is a question of fact turning on the period of non-use, the condition of the premises, any intervening use and the owner's intentions.
Where unauthorised works and an unauthorised use coincide in a listed building, the enforcement position is more serious, as our piece on listed building enforcement notices explains.
Choosing between an application and a certificate
Three routes exist and they answer different questions.
Apply for planning permission where you accept the change is material and want consent for it. The supporting planning statement should still establish the lawful existing use, because the comparison frames the whole assessment.
Apply under section 192 for a certificate of lawfulness of a proposed use where your position is that the change is not material, or is permitted development. The fee is half that of a planning application for the same development, the authority has eight weeks, and a certificate is conclusive for what it describes.
Apply under section 191 where the use already exists and you say it is lawful, whether by permission or by immunity. The burden of proof is yours and the standard is the balance of probability.
Informal advice from the authority is worth having and binds nobody. Where money is going to be spent on the strength of the answer, buy the certificate.
Enter your postcode on PlanScope to see which documents a change of use is likely to need.
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 or a use are lawful. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.
Frequently asked questions
What makes a change of use material?
A change in the character of the use, judged as a question of fact and degree. Activities carried on, hours, numbers of people, vehicle movements, the nature of any process and the effect on the locality all bear on it. No single factor decides it, and section 55 provides no threshold or percentage.
Does a change of use class always mean a material change of use?
No, and the reverse is also true. A change within the same class of the Use Classes Order is excluded from development by section 55(2). A material change of use can occur between two sui generis uses, or within a use that has no class at all, so the two questions are separate.
Why does the planning unit matter?
Because it fixes what is being compared. Introducing a small takeaway counter into a large supermarket may not change the character of the supermarket's use, while the same counter in a small shop changes the character of the whole unit. The approach to identifying the unit comes from the Burdle decision.
Can intensification be a material change of use?
Yes, but only where it alters the character of the use rather than its volume alone. A guest house taking more bookings is still a guest house. A haulage yard going from three vehicles to thirty has probably changed the character of the use of the land, judged on movements and hours rather than the count.
When does an ancillary use become a primary use?
Gradually, and often without anybody deciding. Selling a holding's own produce from a shed is ancillary to agriculture; selling mostly bought-in goods from a converted barn with parking and a cafe is retail. The same pattern appears in workshops becoming trade counters and pubs becoming restaurants.
Should I apply for permission or for a certificate?
Apply for permission where you accept the change is material. Apply under section 192 for a proposed use certificate where your position is that it is not material or is permitted development, at half the planning fee. Apply under section 191 where the use exists and you say it is already lawful.
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.