Part L transitional arrangements on a phased permission

Part L transitional arrangements are decided by building control dates, not by the date of your planning permission. That single point resolves most of the confusion on phased sites. A permission granted in 2021 does not entitle the last plot of a 40-house scheme to be built to the standards that applied then, because the transitional provisions attach to each building and to when work on that building started.

Architects get caught by this when a client bought a consented site with an energy statement written against an older edition of Approved Document L, then builds out over five years. The planning side has not changed. The construction standard has.

Building regulations run on their own clock

Planning permission and building regulations approval are separate consents with separate triggers. For planning, a permission is implemented by a material operation within the meaning of section 56 of the Town and Country Planning Act 1990, and once implemented the permission is good for the whole development.

Building regulations do not work that way. The applicable edition of an Approved Document is fixed by when the building notice, initial notice or full plans were deposited, and then by whether work on that building started within the period the transitional provision allows. Miss the second limb and the newer standard applies, whatever the planning history says.

The 2021 uplift is the version most people are still unpicking, because it changed fabric and services standards, introduced Approved Document O for overheating and revised Approved Document F. The transitional wording attached to it is the reason plot 38 can be built to a different specification from plot 4 on the same site.

What counts as starting work on a building

This used to be argued about. It is now defined, and the definition is specific.

For the construction of a building, work is treated as having started when it is sufficiently progressed, which in practice means the pouring of concrete for the permanent placement of the trench, pad or raft foundations, or the placing of piling for the foundations. Site clearance, setting out, service diversions, access roads and excavation without a concrete pour do not count.

For work to an existing building, the test is different: broadly, 15 per cent of the proposed work having been completed.

Two consequences follow. First, a developer who digs trenches in the week before a deadline and pours in the week after has not preserved the old standard for that plot. Second, the evidence needed is a dated record of a concrete pour or a piling operation, plot by plot, which nobody thinks to collect until the question is asked two years later.

Why phased sites are assessed plot by plot

The transitional provisions for the 2021 changes apply on a building-by-building basis rather than to a development as a whole. That was a deliberate change from the way earlier uplifts were sometimes treated on site, and it is the part most often got wrong.

The practical effect on a long site is a specification that steps partway through. Two house types, same elevations, different wall build-ups, different glazing specifications and different heating systems. Buyers notice, sales staff need a script, and the architect has to hold two sets of construction details without mixing them up.

Plan for it rather than discovering it. If the build programme puts a phase close to a deadline, the decision to accelerate foundations or to accept the new standard should be taken early, because retrofitting a heat pump strategy into a layout designed around a boiler and a small plant cupboard is expensive.

The records a building control body will want

Assemble these per plot, at the time, and keep them with the plot file.

1. The date and reference of the initial notice or full plans deposit, with the building control body's acknowledgement.
2. A plot schedule tying each plot number to that submission.
3. Dated evidence of the foundation pour or piling: inspection records, concrete delivery tickets, photographs with a visible plot marker, and the site diary entry.
4. Confirmation from the building control body that it accepts the plot as having started under the transitional provision.
5. The design SAP or SBEM calculations against the correct edition, and the as-built calculations to match.

That fourth item is worth chasing at the time. An approved inspector's written acknowledgement is much easier to obtain in the month of the pour than in the year of the sale, and a purchaser's solicitor will ask.

Where planning conditions cut across the transition

Planning conditions can impose an energy standard independently, and they frequently do. A condition requiring a stated percentage reduction in regulated carbon emissions, or requiring development to accord with a submitted energy statement, binds you regardless of which Approved Document applies.

Three patterns cause trouble.

A condition referring to "Part L" with no edition. Read strictly, it is imprecise, but the practical answer is to agree in writing with the case officer which edition is meant before the first plot is built.

A condition tied to a submitted Energy Statement that was calculated against an older edition. Where the newer regulations now deliver more than the statement promised, the sensible route is a written confirmation that the condition is satisfied, or a section 73 application to substitute the updated statement. Leaving the mismatch unresolved makes discharge awkward, and the mechanics of that are covered in our note on zero carbon conditions and how they are discharged.

A condition requiring post-completion evidence for each dwelling. Those need a plot-level process from day one, not a scramble at handover.

Overheating is the same story in miniature. Where a permission predates Approved Document O, the Overheating Risk Assessment used at application stage may have used a different method from the one now required, and the planning and building control positions have to be reconciled rather than assumed to match. Our note on overheating assessment for a planning application sets out what councils ask for.

Section 73 changes and the standard that applies

A section 73 permission is a new planning permission, and it can come with updated conditions. It does not reset the building regulations position, because that turns on the building control submission and the commencement of work on each building.

But a design change made under section 73 can affect it indirectly. If the amendment means the work described in the original full plans is no longer what is being built, a fresh submission may be needed for those plots, and a fresh submission carries the current edition. Substituting a larger house type onto an unstarted plot is the clearest example.

Illustrative example: a 40-dwelling site with full plans deposited in May 2022. Plots 1 to 22 have foundations poured before the transitional deadline and are built to the earlier fabric standard. Plots 23 to 40 are poured after it and move to the current edition, which changes the heating strategy and adds an overheating assessment. Midway through, a section 73 application substitutes four larger units on plots 31 to 34, requiring a revised full plans submission for those four, which are then designed to the edition current at that submission.

Keeping the position straight on a long site

One spreadsheet, one owner, updated weekly. Plot number, house type, building control submission reference, foundation pour date, edition applied, planning condition references and their discharge status.

The Future Homes Standard will bring the next step change, and it will carry its own transitional wording. Because commencement dates and transitional definitions have shifted before, check the current Approved Documents and any accompanying circular on gov.uk at the point you fix a specification, rather than relying on a note written for the previous scheme.

And keep the energy statement honest at application stage. A statement that claims compliance with an edition that will not apply by the time the building is built creates a discharge problem for someone, usually the architect.

Browse the energy and sustainability report types to see how the statements fit together across a phased consent.

This is general guidance, not legal advice; check the position with your local planning authority, your building control body 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.