What Extension Can I Build on My Home? A 2026 UK Planning Guide

Deciding what extension you can build often feels like the wrong question to start with. The better starting point is: what does your house type, plot shape, and location actually allow? A detached house on a large plot has options that a mid-terrace on a conservation area street simply does not. This guide works through the main extension types available to UK homeowners in 2026, matched against the situations they suit best, so you can narrow down your options before you spend money on drawings or a planning application.

Throughout, "permitted development" (PD) refers to the national rights that let you build certain extensions without a full planning application, subject to strict conditions. Even PD projects usually need a lawful development certificate to prove compliance, and many still require a formal notification step. Nothing here is a substitute for checking your own council's local rules, but it will help you ask the right questions.

Start With Your House, Not the Extension

Before picking an extension type, answer three questions:

• Is your house detached, semi-detached, or terraced? This changes your maximum depth allowances under permitted development.
• Is your property on "article 2(3) land"? This includes conservation areas, National Parks, Areas of Outstanding Natural Beauty, the Broads, and World Heritage Sites. If yes, several PD rights are cut back or removed entirely.
• Is your house listed? Listed buildings sit outside most permitted development rights regardless of size or location, and any extension will usually need listed building consent as well as planning permission.

Once you know where you stand on these three points, the extension types below become much easier to filter.

Single-Storey Rear Extensions: The Default Choice

For most homeowners, a single-storey rear extension is still the most achievable option, and permitted development rights here are generous.

Under the standard rules, a rear extension can project up to 3 metres beyond the original rear wall for an attached house, or 4 metres for a detached house, without needing anything beyond standard permitted development, capped at 4 metres in height.

Go beyond that and you move into "larger home extension" territory. On a house that is not on article 2(3) land and not on a site of special scientific interest, you can extend up to 6 metres beyond the original rear wall for an attached house, or 8 metres for a detached house, still capped at 4 metres in height. The catch is that anything beyond the standard limits (over 3 metres attached, over 4 metres detached) triggers the neighbour consultation scheme. You notify your council, the council writes to adjoining neighbours, and those neighbours have a window to object. Work cannot start until the council either confirms no prior approval is needed, grants prior approval, or 42 days pass without a decision. It is not a rubber stamp, but it is far quicker and cheaper than a full planning application.

Crucially, these larger allowances do not apply on article 2(3) land. If you live in a conservation area, your rear extension is capped at the standard 3 or 4 metre limits, full stop.

Best suited to: Homeowners wanting a bigger kitchen-diner or open-plan living space, on a plot outside a conservation area, with reasonable rear garden depth and neighbours unlikely to object to loss of light or outlook.

Wraparound Extensions: Combining Rear and Side

If you want to fill the gap between your side return and your rear wall in one continuous build, rather than a simple rectangular rear box, you are looking at a wraparound extension. These are popular on Victorian and Edwardian terraces and semis where the side return is currently a narrow, wasted strip of garden.

Under permitted development, a wraparound extension has to satisfy both the rear and side limits at the same time. That means no more than 6 metres beyond the rear wall (8 metres if detached), or just 3 metres (4 metres detached) on article 2(3) land, and it must be single storey, capped at 4 metres in height. There is also a width restriction: the total extension width cannot exceed half the width of the original house. Go past any of these limits, on rear projection or on width, and the whole thing falls outside permitted development, meaning you would need full planning permission.

Wraparounds are popular precisely because they add significantly more usable floor space than a rear extension alone, often enough to reconfigure an entire ground floor. But the width cap is the detail most homeowners miss when sketching plans on the back of an envelope, so get it checked early.

Best suited to: Terraced or semi-detached houses with an underused side return, where the homeowner wants a substantial kitchen/living/dining reconfiguration rather than a modest bump-out.

Two-Storey Rear Extensions

If a single-storey rear extension does not give you enough space, or you want an extra bedroom or bathroom above an extended kitchen, a two-storey (or "multi-storey") rear extension is the next step up.

Permitted development rights here are much tighter than for single-storey builds. A rear extension of more than one storey must not project beyond the original rear wall by more than 3 metres, and must sit at least 7 metres from any boundary opposite the rear wall. Standard eaves and height limits still apply on top of this.

This is where a lot of homeowners get caught out with existing single-storey extensions. If you already have a single-storey rear extension that projects more than 3 metres, and you want to add a first floor on top, you cannot do it under permitted development. The 3 metre limit applies to the whole two-storey structure, not just the new floor, so this route almost always needs a full planning application.

Best suited to: Homeowners with a modest, code-compliant existing footprint who want additional space over two floors rather than sprawling further into the garden, and whose neighbouring gardens have enough depth to satisfy the 7 metre boundary rule.

Front Extensions: The Route That Rarely Works Under PD

It is worth being blunt about this one: extending forward of your house is very rarely a permitted development option. The rules state that an extension is not permitted development if it goes beyond a wall forming the principal elevation of the original house, or beyond a side elevation that fronts a highway. This includes the invisible line drawn from the end of that wall out to the property boundary, so even a modest porch-style addition set slightly back can still fall foul of the rule if it crosses that line. Corner plots face an additional restriction where a side elevation fronts a highway.

In practice, this means front extensions (bay windows pushed forward, wraparound porches, garage conversions that extend the front line) will usually need a full planning application, regardless of house type or location. It does not mean permission will be refused, but it does mean you should budget time and fees for the process rather than assuming an automatic right to build.

Best suited to: Homeowners prepared to go through full planning permission, ideally with early informal advice from the council on street scene impact before committing to a design.

Upward Extensions: Adding Storeys on Top

For homeowners on a tight footprint who cannot extend outward, adding storeys upward has become a genuine, if conditional, option since permitted development rights were widened for this purpose.

The rules allow a detached, semi-detached, or terraced house to be enlarged with additional storeys built on the principal part of the house: up to two extra storeys if the house already has two or more storeys, or one extra storey if it is currently single storey (such as a bungalow). There are firm limits attached. The house must have been originally built between 1 July 1948 and 28 October 2018, ruling out both older period properties and very new builds. The finished building cannot exceed 18 metres in total height, each new storey is capped at adding no more than 3.5 metres, and on a non-detached house, the new roofline cannot exceed the neighbouring roof by more than 3.5 metres.

Two points make this route different from the extensions above. First, it never applies on article 2(3) land or to listed buildings, no exceptions. Second, even where it does apply, it is never an automatic right; it always requires prior approval from the council, covering matters such as external appearance, the impact on neighbouring amenity, and loss of light. So while this is a genuine permitted development route in principle, treat it as a formal application process, not a "build now, tell the council later" option.

Best suited to: Owners of 1950s to 2010s houses and bungalows on small plots, particularly where outward extension has already been maximised or the garden is too small to extend into.

Conservation Areas: What Actually Changes

If your property sits on article 2(3) land, it is worth being clear about exactly what is restricted, because it is not simply "everything needs permission."

Within a conservation area, standard Class A permitted development rights for house extensions are cut back in three specific ways. Cladding the exterior in stone, artificial stone, pebble dash, render, timber, plastic, or tiles is not permitted development, so re-facing an extension in a different material to the host house will need an application even if the extension's size is otherwise compliant. Extensions beyond any side wall are not permitted development at all, ruling out side extensions and wraparounds under PD entirely. And a rear extension of more than a single storey is not permitted development, meaning any two-storey rear addition needs full planning permission regardless of how modest the projection is.

Put together, this means conservation area homeowners are generally limited to single-storey rear extensions within the standard 3/4 metre depth limits under PD, with everything else (side extensions, wraparounds, two-storey rear additions, upward extensions, re-cladding) requiring a planning application.

Quick Decision Guide

Situation	Most likely route
Detached/semi/terraced, not in a conservation area, wants more kitchen space	Single-storey rear extension, PD, possibly via neighbour consultation
Victorian terrace with unused side return	Wraparound extension, PD if within width and depth limits
Wants an extra bedroom over an existing rear extension	Two-storey rear extension, check the 3 metre and 7 metre rules carefully
Small plot, no room to extend outward	Upward extension via prior approval, if house was built 1948 to 2018
Wants to extend the front of the house	Full planning application in almost all cases
Conservation area property	Single-storey rear only under PD; side, wraparound, two-storey rear and re-cladding need permission

FAQ

Do I need planning permission for a rear extension? Not always. Many single-storey rear extensions fall within permitted development limits. Larger ones (up to 6 metres attached or 8 metres detached) can still avoid a full application but must go through the neighbour consultation scheme first.

Can I add a second storey to my bungalow? Potentially, via the permitted development route for additional storeys, but only if it was built between 1