Working out whether a permitted development right is used up
Class A and Class E allowances are cumulative and attach to the building, not the owner. How to reconstruct the planning history and present a chronology an officer will accept.
Permitted development allowances are cumulative, so the question of whether a permitted development allowance already used by someone else still counts against you has a short answer: usually yes. The limits in Schedule 2 of the General Permitted Development Order are measured against the dwellinghouse as it was originally built, or as it stood on 1 July 1948 if it is older, not against the house as you bought it. Work done by previous owners therefore reduces what is left.
That is why the first hour of any permitted development project belongs in the planning register, not on the drawing board.
Which allowances are cumulative and which are not
The rules differ by class, and the wording in the Order is what governs.
Class A of Part 1, enlargement of a dwellinghouse, works from the original dwellinghouse. Rear extension depth limits are measured from the original rear wall, and the restriction on extending beyond a wall forming a side elevation applies to the original house. An earlier rear extension consumes the depth allowance even if it was built thirty years ago under an express permission.
The 50 per cent curtilage test in Class E, for outbuildings, is also cumulative: the area covered by buildings, enclosures and containers, other than the original dwellinghouse, must not exceed half the area of the curtilage excluding the ground area of the original dwellinghouse. Every shed, garage and garden office counts.
Class B and Class C, roof enlargements and alterations, carry their own cumulative volume allowance expressed in cubic metres, and additions to the roof slope count against it.
A different logic applies to the prior approval classes in Part 3. Class MA and Class Q have limits on floorspace and on the number of dwellings created, and once that number has been used on a building or an agricultural unit, the right is spent. Our note on proving an agricultural building was in agricultural use deals with the evidence side of that.
Earlier work by previous owners
The allowance attaches to the building, not to the owner. Buying a house does not reset anything.
Nor does it matter whether the earlier work was done under permitted development or under an express planning permission. An extension built with permission still occupies part of the original building's footprint allowance for the purposes of the Class A limits, because those limits measure the house as extended against the house as originally built.
The exception is where a permission expressly removed permitted development rights by condition. That makes the position worse rather than better: the right may not exist at all, and a condition removing Class A rights is common on new estates and on infill plots.
Unauthorised work that is now immune
This is the part people get wrong in both directions.
Work that was carried out without permission and is now immune from enforcement action, through the passage of time, is lawful. But it still physically exists, so it still counts when measuring the extended house against the original one. An immune rear extension does not restore your rear extension allowance.
Enforcement time limits are in flux. The traditional position has been four years for unauthorised building operations and for a change of use to a single dwellinghouse, and ten years for other breaches of planning control. The Levelling-up and Regeneration Act 2023 contains provision moving the building operations period to ten years, and whether that change is in force should be verified on legislation.gov.uk before relying on either figure. Where immunity is being claimed, a lawful development certificate under section 191 of the Town and Country Planning Act 1990 is the only formal way to confirm that works are lawful.
Where to find the planning history
Start with the council and work outwards.
- Search the council's online planning register by address and by the previous address format, because older records are often indexed differently.
- Ask the council for a planning history search where the online register starts after a certain year, which is common for records before the 1990s.
- Order the title register and title plan from HM Land Registry, which can show the historic extent of the plot and any restrictive covenants.
- Check the council's building control records, which sometimes capture work that never had a planning application.
- Look at the local studies collection for the area, which often holds large scale historic maps that are not online.
Keep the search result even when it finds nothing. A documented nil return from the register is evidence in itself.
Historic mapping and aerial imagery
Where no paper record exists, the footprint has to be reconstructed from imagery. Ordnance Survey large scale mapping from successive editions shows the building outline over time, and aerial photography from the 1940s onwards is held in a number of public collections.
Three practices make this evidence usable. Date every image and state the source. Scale consistently, ideally by overlaying on a measured survey. And be honest about what cannot be resolved: an image that shows a structure but not its height proves footprint and nothing more.
For a 1930s semi where you need to know whether the rear projection is original, the 1948 position is the one that matters, so the earliest post-war mapping edition is the key document.
Building a chronology an officer accepts
Present it as a dated table with a source column, then a plan showing the original footprint, each addition and the proposal. Officers assessing a permitted development enquiry or a certificate application are looking for exactly that, and they will check your arithmetic.
Include the running totals. For Class E, the curtilage area, the ground area of the original dwellinghouse, the area of each existing building and enclosure, and the resulting percentage. For Class A, the original rear wall position, the depth of each extension, and the eaves and ridge heights. Our note on the 50 per cent curtilage rule for garden outbuildings works through that calculation, and garden offices and the separate planning unit problem covers the use question that sits alongside it.
Where a figure is uncertain, say so and give the range. An officer who sees an honest uncertainty treats the rest of the document as reliable.
Why a certificate protects a future sale
A lawful development certificate for proposed development under section 192 of the 1990 Act confirms that what you intend to build does not need permission. It costs half the equivalent application fee and it takes eight weeks.
Conveyancing solicitors now routinely ask for evidence that permitted development work was lawful, and an indemnity insurance policy is a poor substitute. For work on a property you intend to sell or refinance, the certificate is the document that answers the enquiry in one line rather than in a file of correspondence.
Where the arithmetic is close to a limit, apply for the certificate before building rather than afterwards. The margin between compliant and unauthorised is often a few hundred millimetres, and it is much easier to adjust a drawing than a built wall.
This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it.
Frequently asked questions
Does an extension built by a previous owner use up my allowance?
Yes. The Class A limits measure the house as extended against the original dwellinghouse, meaning the house as first built or as it stood on 1 July 1948 if older. It makes no difference who built the earlier extension or whether it had express planning permission. The allowance attaches to the building.
Does unauthorised work that is now immune count against the limits?
Yes. Immunity from enforcement makes the work lawful, but the structure still exists, so it still counts when measuring the extended house against the original. An immune rear extension does not restore your rear extension depth allowance, and a certificate confirming immunity does not change that arithmetic.
How far back do I need to research?
To the original construction, or to 1 July 1948 for older houses, because that is the baseline the Order uses. In practice that means the council register, building control records, the Land Registry title plan and successive editions of Ordnance Survey mapping, with aerial photography filling the gaps where no paper record survives.
What are the current enforcement time limits?
The traditional position is four years for unauthorised building operations and for change of use to a single dwellinghouse, and ten years for other breaches. The Levelling-up and Regeneration Act 2023 provides for the building operations period to become ten years, so check on legislation.gov.uk whether that change is in force before relying on either figure.
Is a lawful development certificate worth the fee?
Where the arithmetic is close to a limit, yes. A certificate for proposed development under section 192 confirms the works do not need permission, costs half the equivalent application fee and takes eight weeks. Conveyancing solicitors now ask for that evidence routinely, and adjusting a drawing is far easier than adjusting a built wall.
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.