Putney conservation appeal rejects uPVC sash windows

A Putney conservation appeal has upheld Wandsworth Council’s refusal of replacement uPVC sash windows and French doors at a two-flat Victorian building, after a Planning Inspector found that matching the original dimensions would not overcome harm from the substitute material.

The decision, issued on 9th October 2026, concerns 6 and 6A Commondale in the Putney Lower Common Conservation Area. The applicant proposed to replace existing timber sashes and rear French doors with Rehau “Heritage” uPVC units described as matching the originals. The Inspector agreed that similarity in design and measurements did not resolve the loss of traditional timber detailing.

The appeal is a useful reminder that the conservation-area assessment does not stop at colour, glazing patterns or frame profiles. Material character, workmanship, texture and the cumulative effects of individually modest changes can matter, even where some neighbouring properties already have plastic windows.

Putney conservation appeal turns on timber detail

The scheme was submitted by Copperfields 2015 Residential Ltd under Wandsworth planning reference 2026/0118. It proposed the removal of all timber sash windows in the front, rear and side elevations, as well as timber French doors at the rear. Those were to be replaced with Rehau uPVC products intended to replicate the existing appearance.

Planning appeal 6011322 was considered following a site visit by Planning Officer J Reed on 28th August 2026. The final decision was made by Inspector A M Nilsson, who considered the officer’s recommendation and the submitted evidence. The determination was a dismissal of the section 78 appeal, not a committee refusal, a new Article 4 Direction or a ruling that every uPVC replacement is unlawful.

The two-storey property is a late Victorian building converted into two flats. Its setting within the Putney Lower Common Conservation Area was central. Under section 72(1) of the Planning (Listed Buildings and Conservation Areas) Act 1990, decision-makers must pay special attention to the desirability of preserving or enhancing a conservation area’s character or appearance. The decision described the area’s significance as arising from traditional buildings, their relationship with landscape and recurring details such as timber sash windows and doors. It found that the appeal building contributed positively to that character.

In the Inspector’s assessment, the existing windows had slender painted timber frames and glazing bars. Their sashes sat within the frames in a manner consistent with the building’s period design. The proposed alternatives would substitute a different material and finish, despite being offered as dimensionally similar products.

The decision referred to the characteristic “machine-made” appearance of uPVC in contrast with the subtleties and texture of painted timber. It held that the proposed replacements would diminish the architectural cohesion of the building and its conservation-area surroundings.

Why matching the existing windows was not enough

Many window applications focus on elevations, frame thickness, opening patterns and glazing bars. Those are important, but this appeal demonstrates why a purportedly sympathetic profile cannot be judged independently of material. The applicant’s assertion that dimensions and detailing would remain the same was not disputed for the purpose of the decision; the Inspector simply considered it insufficient to avoid the particular harm identified.

The decision also addressed a familiar argument: other properties nearby already have uPVC units. The Inspector accepted that unsympathetic alterations existed locally but did not treat them as an appropriate precedent. Existing poor-quality alterations had themselves eroded the area’s appearance, and repeating them would contribute to further incremental loss.

A local authority cannot simply say that all non-traditional materials are unacceptable without considering the site and proposal. Equally, a developer cannot establish acceptability by pointing to previous departures from architectural character. This is a site-specific balancing exercise, informed by what gives the designated area its significance.

The Inspector identified harm to the conservation area’s character and appearance. Although the visual effect would be localised, that did not make it negligible. The decision categorised the harm as moderate in the language of the August 2026 National Planning Policy Framework, while treating conservation of the designated heritage asset as a matter deserving considerable weight.

The relevance of Article 4 and permitted development

The Inspector also noted the absence of an Article 4 Direction controlling equivalent alterations to dwellinghouses nearby. The Inspector did not regard that as a reason to approve the flats’ replacement joinery. The planning application before the Inspector required determination on its own merits, including the statutory and policy protection of the conservation area.

This distinction matters. An Article 4 Direction may remove specified permitted development rights where they would otherwise exist, but it does not determine the outcome of a full planning application. Nor should the rights available to a dwellinghouse automatically be assumed to apply to a building divided into separate flats. The status of the planning unit and the nature of the external works must be established first.

For a more general explanation of the different rules affecting window changes, see Planning Geek’s guides to windows and doors and altering existing windows. Those starting points do not replace examination of listed status, conservation controls, planning history or any conditions on the particular property.

Energy-efficiency benefits failed to outweigh heritage harm

The applicant advanced energy-efficiency benefits from the replacement products. The Inspector did not reject that improving the performance of the building could be beneficial. Instead, the decision found insufficient evidence that comparable improvement could not be secured by a scheme which preserved the conservation area’s character.

Under the heritage balancing exercise described in the decision, the limited weight given to the energy case did not overcome the identified harm. An applicant relying on retrofit performance therefore needs more than an assertion that new units will be warmer or more efficient.

Useful supporting evidence could include a measured condition survey of existing timber, the extent of decay and repairability, glazing and draught-proofing options, quantified thermal and ventilation performance, and an alternatives assessment. Such material will not automatically secure consent, but it helps the decision-maker understand whether the proposed loss is necessary and proportionate.

An options appraisal may distinguish between retaining and repairing existing sashes, installing compatible secondary glazing, replacing individual damaged components and a complete replacement in timber. Any claimed carbon benefit should also recognise the embodied impact and likely life of the replacement components rather than assuming a plastic replacement is necessarily the sustainable choice.

August 2026 national heritage policy applied

The appeal explicitly addressed the updated National Planning Policy Framework published on 17th August 2026. The Inspector considered that the revised heritage wording did not materially change the assessment in a way that would prejudice either party, so a further consultation was unnecessary.

In particular, the decision applied the Framework’s heritage policy HE6, weighing the effect on a designated heritage asset against public benefits. It concluded that the replacement windows were contrary to relevant requirements in London Plan Policy HC1 and Wandsworth Local Plan Policies LP1, LP3 and LP5, which together seek appropriate design and respect for architectural and historic context.

The site-specific findings are not a general ban on uPVC in conservation areas, nor proof that timber replacement must always be allowed. The material’s finish, extent of replacement, significance of surviving features, visibility from the public realm and quality of alternatives all require proper evaluation.

Practical implications for applications and appeals

For planning consultants, the key lesson is to start with the actual historic or architectural contribution made by the windows. Describe the surviving joinery, identify any later alterations and explain which elements are visible and why they matter. Claims that an installation will look similar from the street should be tested against details, not merely manufacturers’ catalogue photographs.

For property owners and contractors, it is worth resolving planning requirements before committing to procurement. Replacement windows can look straightforward as building work but carry significant heritage implications, particularly where a building consists of flats and the familiar householder rules cannot simply be assumed.

For councils, the decision is also a reminder that reasoning must be anchored in the significance of the particular conservation area. The Inspector explained why timber detailing contributed to this area and why the proposed substitute would erode it, rather than relying on a generic dislike of modern materials.

The appeal did not concern listed building consent or a separate enforcement notice. It also did not establish that existing plastic windows elsewhere were unlawful. It was a planning appeal on the specified replacement scheme, on the evidence put before the Inspector.

The source is the full Planning Inspector appeal decision 6011322, issued 9th October 2026, with the official Planning Inspectorate appeal record available for case tracking. The outcome was dismissal; no planning permission for the proposed uPVC replacement was granted.