Do I Need Planning Permission for an Extension in Wales?
The short answer: many single-storey extensions in Wales can be built without planning permission, provided they stay within permitted development limits. The answer that matters before you spend money on drawings depends on the extension’s size and position, the type of house, and whether the property sits in a conservation area, has an Article 4 direction against it, or has had its rights removed by a previous planning condition.
This guide sets out the Welsh rules in plain English: what applies in Ceredigion and Carmarthenshire, what an application costs, and how long it takes.
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TL;DR
- A single-storey rear extension up to 4 metres deep and 4 metres high usually needs no planning permission in Wales, provided it meets the permitted development conditions.
- Flats, listed buildings and houses in conservation areas (Aberaeron and Cardigan town centres, for example) are treated differently — assume you will need permission.
- A householder planning application in Wales currently costs £585 under the fee schedule in force since 1 December 2025.
- The council has 8 weeks to decide a householder application. Well-prepared applications in straightforward cases are often decided inside that.
- Planning permission and Building Regulations approval are separate — you usually need both.
The quick answer: what permitted development lets you build
“Permitted development” (PD) is a set of national rules that let you extend your home without a planning application, provided the work stays within defined limits. The Welsh Government sets these rules, and they are not the same as England’s — advice from English websites or television programmes does not always apply here.
For a house (not a flat or maisonette), a single-storey rear extension is permitted development in Wales if it meets all of these:
- Depth: it does not extend more than 4 metres beyond the rear wall of the original house — the house as first built, or as it stood on 1 July 1948. Extensions added by a previous owner count towards this.
- Height: no more than 4 metres high.
- Eaves: if any part of the extension is within 2 metres of a boundary, the eaves cannot exceed 3 metres in height.
- Position: nothing in front of the principal elevation (the front of the house), and no extension beyond a side wall that faces a highway.
- Coverage: no more than half of the land around the original house is covered by extensions and other buildings.
- Materials: the exterior materials must, as far as possible, match the existing house.
- No verandas, balconies or raised platforms.
Two-storey extensions can also be permitted development in Wales, but the limits are tighter: the upper floor can project only 3 metres beyond the rear wall, the extension must sit at least 10.5 metres from the rear boundary, upper-floor side windows must be obscure-glazed and non-opening (unless 1.7 metres above floor level), and the roof pitch should match the existing house. Two-storey rear and side extensions are not permitted development in conservation areas, national parks, Areas of Outstanding Natural Beauty or World Heritage Sites. Side extensions have their own conditions, including that the resulting house can be no more than 50% wider than the original.
If your proposal fits within these limits, you can usually proceed without a planning application — though you may still want proof, which we come to below.
When you definitely need planning permission
Some situations remove or override permitted development entirely. If any of these apply, plan on making a householder application:
- Your home is a flat or maisonette. PD rights for extensions apply to houses only.
- The house is listed. Listed building consent is a separate requirement on top of any planning permission.
- The property is in a conservation area, AONB, national park or World Heritage Site. Parts of two-storey extensions lose PD rights altogether, and cladding restrictions apply.
- An Article 4 direction applies.Councils use these, most often in conservation areas, to remove specific PD rights from a group of properties. Aberaeron’s town centre and parts of Cardigan have conservation-area designations where this is a real possibility — it is worth checking before you design anything.
- A condition on a previous planning permission removed PD rights. This is recorded on the planning register, and it is more common than people expect on newer estates and converted properties.
- You have already used your allowance. Previous extensions count towards the 50% garden coverage and depth limits.
The only reliable way to check these is the council’s planning register — we do this as standard on any site visit, because finding out after the drawings are done is an expensive surprise.
The Ceredigion and Carmarthenshire checklist
MGC is based in Aberaeron and works across both counties. These are the checks that come up on real jobs here.
Conservation area?
Aberaeron, Cardigan, Lampeter, New Quay and large parts of Carmarthen’s older quarters all contain conservation areas. Being in one does not stop you extending — most single-storey rear extensions still qualify as permitted development — but two-storey extensions and side extensions lose some or all PD rights, and the council will weigh the design against the character of the area.
Coastal designated landscape?
Stretches of the Ceredigion coast sit within a designated landscape (the Ceredigion Coast AONB), where the same designated-land rules apply.
Article 4 direction?
Check with the planning authority — Ceredigion County Council or Carmarthenshire County Council — before assuming your rights are intact.
Previous applications on the property?
A past approval may carry a condition removing PD rights, or an earlier extension may already have used part of the allowance.
Listed?
Ceredigion and Carmarthenshire both have large numbers of listed Georgian and Victorian houses. If yours is one, expect to need both planning permission and listed building consent.
What a planning application costs in Wales
The council fee for a householder application in Wales is £585, under the fee schedule that took effect on 1 December 2025. Fees are set by Welsh Government regulations rather than by individual councils, so the figure is the same across Ceredigion and Carmarthenshire. The Welsh Government has said fees will not change during 2026, with annual updates from April 2027 — but confirm the current schedule when you apply.
On top of the council fee, you will normally pay for drawings. Scale and complexity vary too much for an honest fixed figure — a proper measured survey at the start avoids expensive revisions later, and any quote for design work should state what is included before you commit.
One further option worth knowing about: even when your extension is permitted development, you can apply for a Lawful Development Certificate. This is not a planning application and does not give permission — it is the council’s formal confirmation that the work did not need it. It costs less than a full application, and it is genuinely useful when you sell, because a buyer’s solicitor can see the paperwork. It is optional, not a legal requirement.
How long planning permission takes in Wales
For a householder application, the council has a statutory determination period of 8 weeks. In practice, a well-prepared application on a straightforward site is often decided within that window; applications that need amendments, extra surveys or neighbour negotiations take longer — the clock stops while the council waits for information.
A sensible sequence for a typical extension looks like this:
Site visit and measured survey
A week or two to arrange and complete.
Drawings and application
A few weeks, depending on the design.
Council determination
Up to 8 weeks from a validated application.
Building Regulations and build
Separate from planning entirely (see below).
So from first conversation to breaking ground, allow a few months rather than a few weeks. It pays to start the planning conversation before you have your heart set on a start date — and to budget realistically for the build itself while you wait (our rear extension cost guide covers what moves the price in West Wales).
Planning permission is not Building Regulations approval
This is the misunderstanding that causes the most problems. Planning permission decides whether the extension should be allowed; Building Regulations approval decides whether it is built properly — structure, insulation, fire safety, damp and drainage. You need Building Regulations approval for almost any extension whether or not it needed planning permission.
For an extension this typically means structural calculations (steel beam sizes, foundation design), building control inspections at set stages, and a completion certificate. A design-and-build company handles this as part of the same job — at MGC, the same team that designs the extension prepares the structural information, books the inspections and finishes the certificate.
How MGC handles the planning side
Because MGC designs and builds under one contract, planning is part of the job rather than a service you commission separately:
- We check permitted development rights, conservation area status, Article 4 directions and the property’s planning history before designing anything.
- If the extension qualifies as permitted development, we tell you plainly — including when the honest answer is “you don’t need to spend money on an application”.
- If permission is needed, we prepare the householder application and manage it through Ceredigion or Carmarthenshire’s planning process, including responding to council queries.
- Building Regulations, structural calculations and inspections are handled by the same team that builds the extension.
Frequently asked questions
Straight answers on permitted development, costs, timelines and certificates for extensions in Wales.
Up to 4 metres beyond the rear wall of the original house, and up to 4 metres high. If any part is within 2 metres of a boundary, the eaves cannot exceed 3 metres. Two-storey extensions have tighter limits and are not permitted development in conservation areas and other designated land.
A householder application currently costs £585 under the Welsh Government fee schedule in force since 1 December 2025. Fees are set nationally and are the same whether you apply to Ceredigion or Carmarthenshire. Always confirm the current schedule when you apply, as fees do change.
The council has 8 weeks to decide a householder application once it is validated. Straightforward applications are often decided within that period; anything requiring amendments, extra reports or extended neighbour consultation can take longer. This is separate from the build itself.
A conservatory is treated the same as an extension under Welsh permitted development rules — within the size, height, coverage and materials limits, no permission is needed; beyond them, it needs a householder application like any other extension.
Usually yes, but with restrictions. In Welsh conservation areas, single-storey rear extensions can still qualify as permitted development if they meet the standard limits, but two-storey rear and side extensions are not permitted development, side extensions must be set back from the front, and an Article 4 direction may remove further rights. Design quality also carries more weight with the council.
The council's formal confirmation that work was (or will be) permitted development and did not need planning permission. It is optional — but it removes doubt for future buyers and their solicitors.
What next
If you are planning an extension in Ceredigion, Carmarthenshire or the surrounding counties, the cheapest point to find out where you stand is before any money is spent on drawings. On a free site visit we check your permitted development rights, conservation area status, Article 4 directions and the property’s planning history, then tell you plainly whether you need an application. More on how we work: extensions and renovations.
Book a free site visit — the check costs nothing and can save an expensive mistake.
Book a free site visit
Book a free site visit — the check costs nothing and can save an expensive mistake.
Planning rules in Wales are set by the Welsh Government and can change; this guide reflects the rules and fee schedule published at the time of writing.