A previously approved side extension was extended further on the ground than the planning drawings allowed — tipping the development out of permitted development and onto the council's enforcement radar.
Our client is the owner of a two-storey link semi-detached house on a corner plot in west London. A few years ago they obtained full planning permission for a single-storey side extension — everything done by the book, drawings approved, decision notice issued. The builder then went to work.
Somewhere between the approved drawings and the finished structure, the builder added a little extra. Not much in the grand scheme of things, but enough to push the side extension out beyond what the council had agreed. The space was originally intended as ancillary accommodation; it now functions as everyday storage for the household.
Eventually a planning case officer visited the site, took measurements, and confirmed in writing that the additional element exceeded what the original consent allowed and what the General Permitted Development Order would otherwise tolerate. The advice was unambiguous: a retrospective application is required.
On the face of it, a small side extension on a domestic property sounds like the sort of thing that should comfortably sit within permitted development rights. On a corner plot, however, the analysis becomes more delicate. The General Permitted Development Order treats the "principal elevation" — the main public-facing front of the house — quite differently from the rest of the property, and it caps the maximum width of any side extension at half the width of the original dwelling.
In short: there was no clever permitted development argument waiting in the wings. The only way to formalise the development was a retrospective application on its planning merits.
This is not a case where the council was upset about what had been built — the case officer's site visit produced careful measurements but nothing that suggested any harm to the locality. The extension is small in scale, set away from neighbouring habitable windows, and entirely consistent with the form and proportion of the original dwelling. The street scene is unaffected. Residential amenity is not compromised.
Our reading was that the application would be approvable on its planning merits, provided it was framed properly. The risk was not refusal — it was drift: a thin or poorly-evidenced application sitting in a busy planning department for months while the homeowner worried about enforcement.
We prepared and submitted a comprehensive householder application that does three things:
Where the property has prior planning history — including earlier applications that were refused before the original side extension was approved — we set that history out openly and explain why the current proposal sits comfortably with the design principles the council has already endorsed.
Alongside the planning statement, we prepared and submitted a full set of scaled architectural drawings — site location plan, block plan, and existing and proposed elevations and floor plans where relevant — giving the case officer a clear, accurate and measurable picture of the development to assess against policy.
When a builder oversteps the drawings, the homeowner is the one who carries the risk. The right response is not to argue about who's at fault — it's to put a proper retrospective application in front of the council quickly, on terms the case officer can actually approve.
Side extensions are one of the most common reasons homeowners end up needing retrospective consent. Sometimes it's a builder; sometimes it's a misreading of the permitted development rules; sometimes it's the corner-plot trap that catches even careful applicants out. Whatever the cause, the route through is the same: a proper application, properly framed, prepared by someone who has read the same rulebook as the case officer.
A Chartered Town Planner will read your decision notice or measurements and tell you, honestly, what your options are.