Advice · Yeovil & Somerset
The gap down the side of a house is often the most under-used space on the whole plot. Turned into a side extension, it can widen a cramped kitchen, add a utility room or create a downstairs WC without eating into the garden. Here is what Yeovil homeowners should know before committing, from planning rules to realistic budgets.
Side extensions suit the semi-detached and detached homes found across much of Yeovil, from the 1930s properties around Preston Road and Larkhill to newer estates at Wyndham Park and Brimsmore. If you have two metres or more between your wall and the boundary, that strip can usually become genuinely useful internal space. Even a narrow return of 1.5 metres can house a utility room, a downstairs loo or a run of storage that frees up the rest of the ground floor.
The most popular use locally is opening up the kitchen. Removing the original side wall and extending outwards typically turns a galley kitchen into a kitchen-diner, often with a wrap-around option if you combine it with a rear extension later. Terraced houses in the town centre are trickier, as most have no side access at all, so a rear or loft project usually makes more sense there.
Many single-storey side extensions fall under permitted development, meaning no full planning application is needed. The main conditions are that the extension is single storey, no more than four metres high, no wider than half the width of the original house, and built in materials that broadly match the existing property. If your home meets these, a lawful development certificate from Somerset Council is worth obtaining anyway, as it gives you paperwork to show when you sell.
You will need a full planning application if you want two storeys, if the house has already been extended, if you live in a conservation area such as parts of central Yeovil or nearby villages like East Coker and Montacute, or if the property is listed. Somerset Council currently aims to decide householder applications within eight weeks, though allow longer if neighbours object. Party wall agreements may also apply where you are building close to a shared boundary, so speak to your neighbour early.
As a realistic guide for the Yeovil area in 2026, a straightforward single-storey side extension tends to come in between £2,200 and £2,800 per square metre for the build itself. A typical 12 square metre utility and WC extension might therefore land somewhere between £28,000 and £38,000, while a larger kitchen extension of 20 square metres with structural openings, glazing and a fitted kitchen can reach £55,000 to £75,000 or more depending on specification.
The figure depends heavily on ground conditions, drainage runs, whether steelwork is needed to open up the existing wall, and your choices on windows, flooring and fittings. Yeovil's clay soils sometimes mean deeper foundations than expected, which is why a proper site survey before quoting matters. Budget separately for planning fees, building regulations inspections, and around 10 per cent contingency for the unexpected.
Light is the main challenge in a side extension, because you are usually building close to a boundary where windows are restricted. Rooflights solve this well, and a run of two or three over a new kitchen brings in more daylight than most side windows ever could. If the extension faces the boundary, obscured glazing or high-level windows keep the space bright without overlooking issues.
Think about the junction with the existing house too. A flat roof with a parapet suits many 1930s properties, while a pitched lean-to in matching tiles often looks better on older stone houses common around South Somerset. Getting the brick or render match right, and lining new floor levels through from the original rooms, is what makes an extension feel like it was always there rather than bolted on.
From first design conversation to completion, allow four to eight months. Design and planning typically take two to three months, and the build itself runs eight to fourteen weeks for a single-storey project depending on size and weather during groundworks.
The good news with side extensions is that most of the disruptive work happens outside the main living space until the final stage, when the existing wall is opened up. A well-planned build sequence keeps your kitchen usable for as long as possible, with the messiest breakthrough work compressed into a short window near the end.
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