Refused for being “out of proportion.” The Inspector disagreed.

London Borough of Hounslow refused a single-storey rear extension on a mid-terrace house on Epworth Road, Isleworth, on the grounds that it was too big for the property and would harm neighbours. On appeal, a Planning Inspector allowed it in full. Here's exactly why the council's reasoning didn't hold up — and what it means if you're facing a similar refusal.

The application

✓Site: a mid-terrace house on Epworth Road, Isleworth (part of a short terrace of four).
✓Proposal: a single-storey rear extension with a pitched roof and four roof windows, projecting 3.6m from the rear of the house.
✓Decision: refused by Hounslow, then allowed on appeal by the Planning Inspectorate.

Why the council refused it

Hounslow gave two refusal reasons, both citing Local Plan Policies CC1, CC2 and SC7:

The extension's depth, scale and bulk would be out of proportion with the house and harm the character of the area.
The same depth, scale and bulk would harm the neighbours at the adjoining properties through loss of light, loss of outlook, and an increased sense of enclosure.

The council's own design guidance sets 3.05m as the depth normally considered acceptable for a single-storey rear extension on a terraced property. At 3.6m deep with a footprint of roughly half the size of the main house, the council judged this scheme bulky and disproportionate.

What the Inspector found

The Inspector allowed the appeal in full, subject to standard conditions. Two things drove the decision:

On proportion: although deeper than the guideline figure, the extension was noticeably wider than it was deep — and that overall shape read as proportionate against the host house and terrace, not bulky. The single-storey addition also clearly stayed subordinate to the taller two-storey house behind it.

On neighbour impact: one adjoining neighbour already had an established garden structure close to the boundary that had a similar screening effect to an extension of comparable depth — so the new extension added little material change there. The other neighbour sat on a wider, more open plot where a more generous depth standard applied, and the extension comfortably met it.

Where the council's assessment fell short

Two gaps stand out when you compare the refusal reasons to the Inspector's decision:

The depth guideline was treated as a limit, not a benchmark. Hounslow's refusal leaned heavily on the extension exceeding the 3.05m guideline figure. But the Inspector's decision makes clear that this figure is exactly that — a guideline, meant to be judged against the specifics of each site, not applied as a hard cut-off. Here, the extension's proportions (wide relative to its depth) mattered more than the raw depth number on its own.

The refusal didn't engage with what was actually on the ground next door. The council's reasons treat the neighbour impact as a straightforward consequence of the extension's size. They don't mention the existing structure already sitting at the boundary of the adjoining property — a detail that turned out to be central to the Inspector's reasoning, since it meant the real-world change in outlook and light for that neighbour was far smaller than the refusal reason implied.

What this means for other appeals

✓A guideline figure being exceeded isn't the end of the argument. If your refusal cites a depth, height or footprint guideline, check whether the council treated it as an absolute limit rather than weighing the actual proportions of the scheme.
✓What's already next door matters. Existing sheds, pergolas, fences, or extensions on a neighbouring plot can genuinely change how much impact a new extension actually has — and a refusal reason that doesn't account for them may be resting on an incomplete picture.
✓Check which standard actually applies to each neighbour. End-of-terrace and corner properties are sometimes assessed against a different, more generous guideline than a straightforward mid-terrace neighbour — worth confirming rather than assuming the same figure applies all round.

Think your refusal has a similar gap?

Send us your decision notice and we'll give you an honest read on whether the council's reasoning holds up — and how similar cases nearby have fared on appeal.

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