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Planning guide

Additional-storey planning research

An additional storey materially changes height, massing and often the property’s relationship with neighbours. The assessment should combine route eligibility with design, structure, streetscape and genuinely comparable upward-extension cases.

Written and reviewed by Propeteer Research TeamPublished Reviewed

At a glance

Key facts

Material change
Height, massing and target property size
Potential route
Permission or a qualifying prior-approval route
Valuation consequence
Compare the completed larger home, not just the existing one

A reliable process

How to approach the question.

  1. 01Define the proposed height, roof form, added area and accommodation.
  2. 02Check route eligibility, exclusions and local designations.
  3. 03Compare upward extensions on similar buildings and plots.
  4. 04Review neighbour, daylight, heritage, servicing and structural evidence.

Worked example

Turning a bungalow into a two-storey home

The relevant end-value evidence is a completed home of the target size and room mix, subject to local ceiling and design quality. Simply applying a small renovation percentage to the bungalow misses the scale of the change.

What this does not prove

  • Planning research cannot confirm structural capacity.
  • Prior approval still involves defined matters and eligibility tests.
  • Large schemes need measured design and professional cost advice.

Method used

  • Confirm the subject property and distinguish applications at the address from wider local context.
  • Classify proposal type and outcome consistently, keeping pending, withdrawn and approved-with-conditions cases separate.
  • Give more weight to recent, similar and well-documented decisions; retain contradictory evidence rather than hiding it.

Primary sources and official guidance

Planning PortalPlanning PortalLocal planning authority registersUK local planning authoritiesNational Planning Practice GuidanceDepartment for Levelling Up, Housing and Communities

Source scope, licensing, refresh expectations and known limitations are listed in the public data-source register.

Related guides

How to assess planning-permission likelihood

Build an evidence-led view of planning prospects from policy, constraints, local precedents, conditions and the details of the proposed work.

Which planning-application documents matter

Prioritise decision notices, officer reports, drawings, design statements and specialist reports when researching a planning application.

Apply this guide

Start with the exact UK address.

Research a property