Barnet’s Residential Design Guidance contains unusually specific measurements for dormer windows.
A rear dormer should normally be set at least one metre from the party wall, remain secondary to the roof and occupy no more than half the width and half the depth of the roof slope.
This proposed dormer in Cricklewood failed several of those tests. Barnet refused planning permission, but the inspector found that its conflict with the guidance did not justify refusal.
Why full planning permission was required
The property is the upper flat in a two-storey semi-detached building on Caddington Road.
The owners wanted to extend into the roof by adding a rear dormer with a Juliet balcony. Two rooflights would also be installed on the front roof slope.
Had the property been a single house, a rear dormer might have been possible under permitted-development rights. But those rights do not generally apply to flats, so a full planning application was required.
Barnet refused it.
Why Barnet objected to the dormer
The council’s objection concerned the character and appearance of the building and surrounding area.
Measured against Barnet’s guidance, the dormer was too wide, too deep and too close to the party wall. The council considered those departures sufficient to make it an excessive and unsuitable addition to the roof.
The inspector agreed that the proposal conflicted with parts of the guidance. But that was not the end of the assessment.
Why the dimensional breaches were not decisive
Although large, the dormer was positioned below the ridge, raised above the eaves and set in from both sides.
It would therefore remain contained within the rear roof slope rather than appearing to dominate the roof as a whole.
Its relationship with the building mattered more than a simple comparison with the measurements in the design guide.
Visibility also mattered
The dormer would not be visible from Caddington Road.
Views from the houses behind would also be limited. An existing two-storey rear wing would screen much of the dormer, while the relatively short gardens made it difficult to obtain a clear upward view of the roof.
Sizeable dormers were already part of the surrounding roofscape. The proposal would therefore not appear as an isolated or unfamiliar feature.
The inspector found no material harm to the character of the building or the surrounding area.
Guidance did not decide the application
The inspector concluded that:
“A conflict with some of the guidance within the SPD is insufficient to withhold planning permission.”
Barnet’s guidance was an important consideration, but it did not determine the application by itself. The inspector still had to assess the dormer’s actual effect on the building and surrounding area.
In this case, the dimensional departures identified by the council did not translate into any unacceptable visual harm.
What this decision means
Barnet’s dormer refusals frequently refer to the measurements in its Residential Design Guidance. Those standards matter, but they are not automatic pass-or-fail rules.
A dormer that departs from the preferred dimensions may still be acceptable where it remains contained within the roof, has limited public visibility and causes no material harm to the building or surrounding area.
The central question is not simply whether a proposal meets every measurement. It is whether the departure produces the harm the guidance is intended to prevent.
Has Barnet refused your dormer or loft conversion?
If Barnet has refused your dormer or loft conversion on character grounds—or because it does not meet the council’s preferred measurements—send us the decision notice and plans for a free initial assessment.
We will tell you honestly whether we think an appeal is worth pursuing. Our fixed fee for a suitable Part 1 appeal is £399, and we win more than half of the appeals we take on.
Read more about planning appeals in Barnet or see our guide to appealing a dormer or loft-conversion refusal.