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Routine householder planning applications in England are to be processed in four weeks instead of eight, according to a government announcement on 30 October 2026 that introduced an AI assistant called PlanAssist alongside new delegation rules [1]. For anyone weighing up Wimbledon extension planning in November 2026, the change arrives at the same time as a Savills forecast that prime values in the London suburbs will fall 3.5% in 2027 [2]. Together, those two facts explain why many owners in SW19 and the wider borough of Merton are choosing to improve rather than move. Faster planning decisions do not remove the other steps that must happen before builders arrive, and this article sets out what they are.
Key Takeaways
- PlanAssist, an AI tool for planning officers, is being expanded from three councils to 15, with the government intending every council in England to have it by the end of 2027. It is not yet confirmed for Merton [1][3].
- Early testing cut time spent on key planning tasks by 58%, and the stated aim is to halve routine householder decisions from eight weeks to four. Qualified officers still make the final decision [1][3].
- From 31 October 2026, the National Scheme of Delegation means householder applications such as extensions and lofts must be decided by officers rather than a planning committee [1][4].
- Savills forecasts London suburb prime values to fall 3.5% in 2027 before rising 1.5% in 2028 and 7.5% over five years to 2031 [2].
- Planning is only one gate. Party wall notices, a pre-works survey, structural checks and building regulations approval all still apply, whatever the planning timeline [5][6].
Why Wimbledon extension planning in November 2026 looks different
Two separate policy changes landed on the same day. The first is the National Scheme of Delegation, which took effect on 31 October 2026 and standardises which planning decisions go to officers and which go to committee [1][4]. The second is PlanAssist, an AI tool built with Google DeepMind, Google Cloud and Faculty that brings an application, local policies and site constraints into one place and produces an evidence-backed initial assessment for a trained officer to review [1].
Propertymark, the estate and letting agents' trade body, reported on 5 November 2026 that the tool is aimed at the work Wimbledon homeowners commission most often: extensions, loft conversions and conservatories [3]. The government says householder applications make up nearly 70% of all planning applications each year and around 70% of officers' workload [1].
For a Victorian terrace in Wimbledon Park, a 1930s semi in Raynes Park or a detached house near the Common, the effect is the same. If a scheme needs full planning permission, the decision route is now officer-only, and processing time may shorten once Merton receives the tool.
What PlanAssist does and does not do
The numbers from early testing
The government's press release states that early testing with Camden, Barnet and Dorset councils reduced time spent on key planning tasks by 58% [1]. Propertymark repeats that figure and the eight-weeks-to-four target [3]. This comes from a limited trial, not a national average, and the four-week figure is a stated intention rather than a guarantee.
The rollout is now expanding to 12 more councils for 12 months, including Lambeth, Redbridge and Westminster in London [1]. Merton is not on that list. The government's stated intention is that every council in England will have access to PlanAssist by the end of 2027, so Merton would receive it on that timetable if the rollout proceeds as announced [1][3]. Until then, Wimbledon applications are processed under the existing system, although the delegation changes already apply.
Officers still decide
Both the government and Propertymark stress that the tool assists rather than replaces officers. In Propertymark's words, "qualified planning officers will remain responsible for reviewing assessments and making final decisions" [3]. The government describes the software as optional and used alongside the normal process rather than mandated [1].
"PlanAssist puts AI to work by freeing planning officers to spend more time deciding on applications.", Owen Larter, Senior Director, Frontier AI Policy and Global Affairs, Google DeepMind [1]
Propertymark welcomed faster processing for smaller applications but questioned whether larger developments will see similar gains, and called for more investment in planning services [3]. The government points to 420 newly recruited planners through its backed programmes as part of the answer [1][3].
The National Scheme of Delegation in plain terms
The delegation scheme matters more immediately for Wimbledon, because it is already in force. According to a legal explainer by Freeths, householder applications sit in Schedule 1 of the scheme, which means they "must be decided under delegated powers to officers and cannot go to committee," apart from limited council own-interest cases [4]. Larger or more complex applications sit in Schedule 2, where officers decide unless a statutory significance test is met and both a nominated officer and a nominated committee member agree to send the case to committee [4]. Planning committees are also capped at 13 councillors [4].
Removing the committee route takes away a common source of delay. It does not change the policy tests. A rear extension in a Merton conservation area, or a large rear dormer on a prominent street, is still judged against the local plan and national guidance.
Improve, don't move: the market backdrop
Savills' latest prime forecasts, reported by Property Industry Eye on 9 November 2026, give the London suburbs the sharpest expected fall of any prime market: 3.5% in 2027, followed by 1.5% growth in 2028 and 7.5% growth over the five years to 2031 [2]. Outer prime London is forecast at -2.5% in 2027, +2.0% in 2028 and +9.7% over five years [2]. Savills names elevated mortgage rates, higher taxes including stamp duty, and economic and political uncertainty as the main drivers [2].
"The prime markets are down, not out.", Frances McDonald, Director of Residential Research, Savills [2]
A forecast is a forecast, and Savills' figures apply to prime markets rather than every Wimbledon street. The direction of travel is still clear. When moving costs are high and short-term values are soft, adding a bedroom in the loft or opening up the ground floor often makes more sense than selling. Savills also notes a shortage of suitable family houses in outer prime London, which could limit price falls there [2].
Wimbledon extension planning November 2026: the steps planning does not cover
A faster planning decision is welcome, but it is one gate among several. The following remain the homeowner's responsibility.
Party wall notices
Most extensions and loft conversions in Wimbledon's terraced and semi-detached streets are notifiable under the Party Wall etc. Act 1996 [6]. The RICS consumer guide explains that notice "must be provided either one month or two months before starting work, depending on the nature of the works" [5]. Under the Act, one month applies to a new wall built at the boundary and to excavations within three metres of a neighbour's structure (or six metres below a 45-degree line); two months applies to work on an existing party wall, such as cutting in steel beams for a loft [5][6].
If a neighbour does not consent in writing within 14 days, a dispute arises under the Act. The owners then either appoint one agreed surveyor or one each, and a party wall award must be in place before notifiable work starts [5]. A surveyor appointed under the Act must act impartially regardless of who appointed them [5]. Serving notices early, ideally when the planning application goes in, stops the party wall timeline from becoming the critical path.
Pre-works building survey
Before committing to a design, an independent RICS-regulated surveyor can inspect the existing structure for damp, movement, roof condition and drainage. On older Wimbledon housing stock, a shallow foundation or a bowed party wall can change the engineering approach. A schedule of condition of the neighbouring property, recorded before work starts, also protects both sides if a dispute arises later [5].
Structural checks for lofts
Loft conversions typically involve new steel or timber beams bearing onto party walls, a new floor structure and changes to the roof. A structural engineer's calculations are needed for building control and often inform the party wall notice, because cutting into a party wall to support beams is a two-month notice item [6].
Building regulations approval
Planning permission and building regulations approval are separate. Even where an extension is permitted development, it still needs building control sign-off for structure, fire safety, insulation and drainage. This is unaffected by PlanAssist.
Updated valuation afterwards
Once the work is complete, an updated RICS valuation records what the improvement has done to market value. This is useful for remortgaging, insurance and future sale planning, particularly when Savills expects suburban prime values to dip before recovering [2].
Sequencing the work
The point is sequencing rather than speed. The elements that run in parallel with planning, such as party wall notices, structural design and building regulations, should start when the application is submitted, not after the decision arrives. If Merton's processing time does fall towards four weeks once PlanAssist is in place, a homeowner who has not yet served party wall notices will simply have swapped one delay for another.
FAQ
Does Merton Council already use PlanAssist?
No. The published rollout covers Camden, Barnet and Dorset plus 12 named councils, and Merton is not among them [1]. The government has said it intends every council in England to have the tool by the end of 2027, so Merton would receive it on that timetable if the plan proceeds [1][3].
Will my extension still go to a planning committee?
For a standard householder application, no. Under the National Scheme of Delegation in force from 31 October 2026, householder applications fall within Schedule 1 and must be decided by officers [4]. Exceptions are narrow, such as applications made by the council or its members [4].
Do faster planning decisions shorten the party wall process?
No. The Party Wall etc. Act 1996 is separate from planning. Notice periods of one or two months still apply, and a party wall award is still required where a neighbour dissents [5][6]. Serving notices early is the only way to keep the two timelines aligned.
Is a loft conversion a good investment if values are forecast to fall?
Savills forecasts a 3.5% fall in London suburb prime values in 2027 but 7.5% growth over five years to 2031 [2]. A forecast is not a guarantee, and the right answer depends on the house and the budget. An independent valuation before and after the work is the most reliable way to judge the outcome.
Conclusion
The arrival of PlanAssist and the National Scheme of Delegation marks a genuine change in how routine householder applications are handled in England. For Wimbledon owners, the delegation rules apply now and the AI tool is expected to follow by the end of 2027 if the rollout goes to plan. Faster decisions, set against a Savills forecast of a short-term dip in suburban prime values, strengthen the case for improving rather than moving.
What does not change is the work around planning. Practical next steps are to commission a pre-works building survey, serve party wall notices as soon as a scheme is settled, line up structural calculations and building regulations approval, and book an updated valuation on completion. Wimbledon Surveyors' independent RICS-regulated surveyors can advise on building surveys, party wall matters and valuations across Wimbledon, Merton and south-west London. Starting that work alongside the planning application is the simplest way to make sure a faster decision leads to an earlier start on site.
References
- Ministry of Housing, Communities and Local Government, "Faster planning decisions as new rules and AI tackle delays", GOV.UK, 30 October 2026. gov.uk.
- Property Industry Eye, "Estate agents face another year of falling prime house prices, Savills warns", Property Industry Eye, 9 November 2026. propertyindustryeye.com.
- Propertymark, "AI tool to speed up planning decisions for homeowners", Propertymark, 5 November 2026. propertymark.co.uk.
- Stephan Vargas-Pritchard, "A new era for planning decisions: The National Scheme of Delegation explained", Freeths, 11 June 2026. freeths.co.uk.
- RICS, "Party walls: consumer guide", Royal Institution of Chartered Surveyors. rics.org.
- UK Parliament, "Party Wall etc. Act 1996", legislation.gov.uk. legislation.gov.uk.