Extending a terraced house: what's actually possible
Most terraces can take a single-storey rear extension or a side-return under permitted development — no planning application needed, as long as you stay inside the limits. The things that catch people out are rarely the planning rules. They are side access, light, and the fact that you probably share a wall with two neighbours, not one.
The options that suit a terrace
Terraced houses extend well when you work with their shape. Three jobs fit them naturally: a single-storey rear extension, a side-return that fills the old outrigger alley on a Victorian or Edwardian terrace, and a loft conversion. Combine a rear extension with a side-return and you get a wraparound, which opens up the whole ground floor — that is where the planning gets harder, so treat it as its own decision rather than an easy add-on.
A two-storey rear extension is possible on many terraces and gives you the most floor area for the money, because the foundations and roof cost much the same whether you build one storey or two. What you usually cannot do on a mid-terrace is extend out to the side in the ordinary sense: there is no land there. An end-of-terrace is the exception, and often has the most room to grow — if you are at the end of a row, a side extension is genuinely on the table.
What permitted development allows on a terrace
A lot of terraced extensions need no planning application at all, provided they stay inside the permitted development limits for what the Planning Portal calls “any other house” — its term for anything that is not detached. A terrace counts as any other house, so these are the figures that apply to you.
| Project | Limit for a terraced house | Notes |
|---|---|---|
| Single-storey rear extension | up to 3m deep from the original rear wall | up to 6m via larger home extension prior approval |
| Height, single-storey rear | 4m overall | eaves no higher than 3m within 2m of a boundary |
| Two-storey rear extension | up to 3m deep | not within 7m of the rear boundary; upper side windows obscure-glazed |
| Side extension | single storey, up to half the width, 4m high | only realistic on an end-of-terrace |
| Coverage | no more than 50% of the land around the original house | outbuildings and earlier extensions count |
| Householder planning fee, England | £548 | from 1 April 2026, if you do need an application |
Sources: Planning Portal permitted development guidance for extensions; GOV.UK Permitted Development Rights for Householders technical guidance; GOV.UK fees for planning applications in England from 1 April 2026. “Original house” means the house as first built, or as it stood on 1 July 1948 — a previous owner's extension counts against your allowance.
Two things remove or shrink these rights, and both are common on terraces. Conservation areas take away side-extension permitted development entirely and tighten the rest; a large share of the country's terraces sit inside one. And some streets have had permitted development removed by an Article 4 direction. Checking both with your local planning authority takes ten minutes and is worth doing before you pay for a single drawing. If you build to the edge of the limits, a Lawful Development Certificate is worth the modest fee — it is the council confirming in writing that you did not need permission, which a buyer's solicitor will ask for years later.
The party wall problem is bigger on a terrace
This is the part people underestimate. You share a wall on at least one side, and on a mid-terrace on both, so almost any extension that sits against a shared wall or digs foundations near it brings the Party Wall etc. Act 1996 into play. Being entirely on your own land does not exempt you.
Two triggers matter. Building on or against the party wall needs two months' written notice to the adjoining owner. Excavating within 3m of a neighbour's structure and deeper than their foundations — or within 6m and cutting a line drawn down at 45 degrees from the base of their foundations — needs one month's notice. If the neighbour consents in writing within 14 days you can get on with it. If they do not respond or they object, a dispute is “deemed” to exist and each side appoints a surveyor to settle the terms in an award. On a mid-terrace you may be serving two sets of notices, to the house on each side. Build four to eight weeks into your programme for this, and longer if a neighbour digs in. It is a separate process from planning — having permission does not cover you, and neither does a party wall award grant you permission.
Access and light: the constraints you can't change
The rules are only half the story. On a mid-terrace there is no side gate, so every bag of spoil and every pallet of bricks comes through the house or over the rear boundary. That is slower and more expensive to build than the same extension on a detached house, and it is the first thing a sensible builder will ask about. If a neighbour will let you take materials along the rear, say so early; it changes the quote.
Light is the other constraint. A deep rear extension on a narrow terrace can leave the middle of the house dark, which is exactly why side-returns with glazed roofs and rooflights are so popular — they bring daylight into the plan rather than just adding depth at the back. Before you fix the layout, think about what the new space costs you elsewhere: losing the only downstairs WC, or the understairs store, to make a kitchen-diner work is a common regret. A good design moves those rather than deleting them.
What it costs, and whether it's worth it
As a rough guide, a single-storey rear or side-return extension on a terrace tends to land around £2,100 to £3,000 per square metre of floor area, with the higher end reflecting structural glazing, a steel or two and a good kitchen fit-out. A wraparound or two-storey build costs more in total but often less per square metre. Those figures come from BestBuilders' 2026 regional cost model — published national cost guides multiplied by a regional labour index, averaged across 519 UK towns — and they are indicative, not a quote. For a breakdown by size and finish, see BestBuilders' terraced house extension cost guide or our own house extension cost page.
On value, be honest with yourself. A terrace is usually worth less than a semi or detached house in the same area even after you extend, and most streets have a ceiling price that a kitchen extension will not push through. Extend for the space you will actually live in — a proper kitchen-diner, a third bedroom in the loft — and treat any resale gain as a bonus, not the reason.
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