Architect’s Insight: Is It Permitted Development?

“Is it permitted development?”

I get asked this on a weekly — if not daily — basis. And my answer is always the same… “Maybe.”

It’s not the answer people are hoping for, but it’s the honest one. And more often than not, that answer is quickly followed by another question: Do I need a lawful development certificate?

▶︎ Learn More: Welsh Government Technical Guidance - Permitted development for householders

“Do I need a lawful development certificate?”

The reality is that permitted development in Wales is rarely as straightforward as people assume. There’s a common perception that you can build a certain size extension or carry out specific works without planning permission and that’s the end of it.

In practice, it’s far more nuanced.

Across North Wales — whether in Denbighshire, Flintshire, Conwy, Gwynedd or Wrexham — I regularly see homeowners, builders and even other professionals misunderstand what permitted development actually allows. And more often than not, that misunderstanding comes down to one thing: The detail.

What Permitted Development Means in Wales

Permitted development rights allow certain types of work to be carried out without the need for a full planning application. In Wales, these rights are set out under the Town and Country Planning (General Permitted Development) Order and are intended to simplify relatively minor changes to your home.

On the surface, it sounds simple — a set of rules you can follow to avoid planning permission.

But those rights come with conditions, limitations and exceptions. And it’s those finer details that determine whether something genuinely qualifies as permitted development or not.

In many cases, even where a proposal does fall within permitted development, I still advise clients to obtain a Lawful Development Certificate. This isn’t planning permission, but it provides formal confirmation from the local authority that the proposal is lawful. It removes uncertainty, reduces risk, and is often important when selling or refinancing a property.

Why the Answer Is Almost Always “Maybe”

When someone asks whether something is permitted development, they’re usually expecting a clear yes or no. But the answer depends on a number of variables:

• The type of property

• The location and any planning designations

• The history of the site and previous extensions

• And most importantly, the specific design being proposed

Two schemes that appear almost identical can have completely different outcomes once these factors are considered.

That’s why relying on general advice — or assuming something is acceptable because “someone else has done it” — can lead people in the wrong direction. Permitted development in Wales isn’t about broad assumptions; it’s about how the rules apply to a very specific proposal.

The Core Rules — and Where People Go Wrong

There are a number of key parameters that most people are aware of when it comes to permitted development.

For rear extensions, this typically includes how far you can project beyond the original house — usually up to around 4 metres for detached properties and 3 metres for others. Height also plays a critical role, with single-storey extensions generally limited to around 4 metres overall, and tighter restrictions where the building sits close to a boundary.

Materials must usually be similar in appearance to the existing property, and there are limits on how much of the plot can be covered by extensions and outbuildings.

These are the headline rules — and they’re often where people stop.

But in reality, this is only part of the picture. Many schemes that appear to comply at a glance can fall outside permitted development once the detail is properly considered.

Where Permitted Development Gets More Complex

The more challenging aspects of permitted development are often the ones that aren’t immediately obvious.

One of the most important is the concept of the “original house”. All allowances are measured against the property as it stood when first built — not as it exists today. Previous extensions, even historic ones, all count towards what is permitted.

Roof design is another area where things can quickly become more complex. Loft conversions, for example, are governed by strict limits on roof volume and form. What might seem like a modest addition can easily exceed those limits depending on how the roof is altered.

And then there’s the detail of the design itself. Small changes — a slight increase in ridge height, adjustments to roof pitch, the positioning of rooflights, or even internal floor levels — can all determine whether a scheme falls within permitted development.

This is usually where projects succeed or fail.

Context, Risk and the Role of Lawful Development

Location plays a significant role. Across Denbighshire, Flintshire, Conwy, Gwynedd and Wrexham, there are many situations where permitted development rights are restricted or removed entirely — particularly within conservation areas, for listed buildings, or in designated landscapes.

This is where assumptions can become risky.

Proceeding on the basis that something is permitted development, without properly testing it, can lead to delays, additional costs, or the need for retrospective applications. In some cases, it can result in enforcement issues.

This is why confirming the position upfront is so important. Even where a proposal appears to fall within permitted development, a Lawful Development Certificate provides formal confirmation from the local authority that the works are lawful before they are carried out.

It removes uncertainty at the design stage, ensures the proposal has been properly assessed against the regulations, and avoids the risk of issues arising once work is underway. It also plays an important role later on — when selling a property, evidence is often required to demonstrate that works were lawful, and a certificate provides that reassurance to buyers and solicitors alike.

Final Thoughts

So, is it permitted development?

Permitted development in Wales is a valuable tool when used correctly, but it isn’t a shortcut and it isn’t something that can be judged on size alone.

Every project needs to be considered in full — the property, the site, the planning context and, most importantly, the detail of the design.

If you’re planning a project in North Wales — whether in Denbighshire, Flintshire, Conwy, Gwynedd or Wrexham — it’s always worth asking the question properly. Not just: “Is it permitted development?” but “Is it permitted development, and should it be formally confirmed through a lawful development certificate?”

Because that’s where the real answer lies.