Do you need Planning Permission?

A Guide to Permitted Development Rights


There are many ways to renovate or extend your home without the need for Planning Permission. This is called Permitted Development.

Permitted development rights apply to most properties, however they may be restricted if your home is in one of the following categories:

If any of the above apply to your project, then you should contact the planning department at your local authority for further information.

Your Local Authority may provide a service which will provide formal confirmation that your project can be carried out under permitted development rights (usually for a fee). If this is not possible you can apply for a lawful development certificate (for a fee) from your local planning authority to prove your development is permitted development. These documents are especially useful in circumstances such as the sale of a property.

In this document we have put together some information to how permitted development rights may apply to common domestic projects. This information is only intended as a guide and we would always



A single storey extension may be acceptable under permitted development rights if:



A loft conversion may be acceptable under permitted development rights if:



A two storey extension may be acceptable under permitted development rights if:



A porch may be acceptable under permitted development rights if:



Development of outbuildings may be acceptable under permitted development rights if:

Do I Need An Architect?

So you’ve decided you want a new extension, but where to start? The big question we often get asked at an early stage is “Do I need an Architect?” The short answer is… it depends.

If the project is very small and very straightforward, it is entirely possible that your building work can be undertaken by a builder without the need for drawings or the involvement of an Architect. Most of the time, however, the form and extent of the building works are not pre-determined, and some design work is required, if for nothing else than to accurately define what the builder is pricing for. Depending on the size and complexity of the project, this drawing work can include everything from initial sketches, through Planning drawings, to Technical drawings to satisfy Building Regulations and for the builder to price and build from. For everything other than the most basic extensions, this is more than simple ‘drawing work’ and involves some design, whether it is basic space planning, conceptual design sketches, or detailed technical design.

So, assuming the project isn’t very small, it is definitely best to have some design drawings, but does an Architect need to do them? Unlike in some countries in the world, there is no requirement by law for an Architect to be involved in a project, and there is also no protection of the function of an Architect. That means that anyone is allowed to perform the job of an Architect. They are not, however, allowed to call themselves an Architect. Under the Architects Act, only people who have undertaken the relevant training and paid their dues to the Architects Registration Board are allowed to call themselves an Architect. As such, you will find a lot of ‘architectural designers’ on the market, who are not Architects.


So what’s the big deal?

Why not hire an ‘architectural designer’ to do your drawing work for a fraction of the price? There are several reasons, but in short, you have no protection or reassurance that they are competent.

To be a registered architect, you have to undertake approximately 7 years of training, usually involving two separate University degrees, and two stints of on-the-job training. Much of this focuses on the ‘Design’ side of things, but the final professional examinations cover many crucial aspects of the work like contract administration, health and safety, project management, dispute resolution etc.

Architects are also bound by the ARB’s Code of Conduct. This deals with all kinds of aspects including Honesty, Integrity and Competence. Any architect who falls short of the requirements can be reported to the ARB who will hold disciplinary procedures and they have the power to reprimand, issue a hefty fine or remove the architect from the register.

Another key requirement of the Code of Conduct, is the requirement to maintain appropriate Professional Indemnity Insurance. This is important because it protects both the Architect and the Client. If the Architect is negligent and disaster strikes, you may seek legal action and be awarded compensation. The compensation awarded is entirely likely to be more than the Architect can pay, meaning the Architect is bankrupted, and the injured party does not receive all that is due to them. If the Architect is insured, the insurance company pays this compensation.

There is no legal requirement for ‘architectural designers’ to maintain Professional Indemnity Insurance, or have any design, technical or professional training whatsoever. There is also nobody to complain to if the service falls short of the level expected. This means the Client may be unprotected if something goes wrong. There’s nothing to say that some ‘architectural designers’ might have PII or be competent at their job, but the Client needs to be very careful.

In addition to the Architects Registration Board, there is the Royal Institute of British Architects, or RIBA, which you are likely to have heard of. Unlike the ARB, there is no requirement to be a member of this, it is purely a members organisation. They do, however, have their own, even stricter standards and codes of conduct.  RIBA Chartered Architects and Practices are required to comply to a wide range of policies from Health & Safety, Quality Management & Equality.


Where to find an Architect

If you want to hire an Architect and you are not sure whether an individual is a registered Architect, you can visit and search the register. You will find all four of the partners at Carve Architecture. Similarly, you can search the RIBA’s website for Chartered Practices at where you will also find Carve Architecture.


Cost of Domestic Extensions

NOTE: This article was originally written in 2020, including projects completed prior to this. See note at bottom of page.

One subject that comes up on every project is, of course, cost. We all only have a certain amount of money, and want a clear idea of how far our budget can go. It is always a hard one to tackle, as every project is different, and every client has differing needs and levels of specification. We are not cost consultants, and the best way to get an accurate price is to speak with a number of builders. That said, what we can do is look at past projects and see what price they came to.

For this piece, we have chosen to look at a number of examples from the past few years of extensions we have completed in and around York. Each of these have an element of extension and some refurbishment of the existing house. To make for a fair comparison, we have discounted some of the more variable aspects of work, namely:

We have then made an assumption that the costs of the refurbishing elements of the house are at a rate of rds that of the extension. We have assumed that loft conversions, needing new floor construction, dormer windows, insulation etc are at the same rate as extensions. It is a fairly crude tool, but the best approach without going into full detail, and useful as a guide.


Case Study 1

Case Study 2

Case Study 3

Case Study 4

Case Study 5

Case Study 6

As can be seen from the figures, there is some variation, which reflects a number of things, including complexity of project and also economies of scale. Looking at the full house refurbishments, they generally are able to achieve a better overall rate compared to smaller extensions which have more foundations, insulation, structure per floor area than the larger projects. Generally, we are finding the rates for extensions are in the region of £1,400-£1,900/m2 with refurbished areas at £950-£1,300/m2. There are some outliers where an extremely cheap or expensive rate is achieved, but these are the exceptions. There may be several reasons why these don’t fit in the normal pricing banding. The expensive one was a high spec job, in particular with the glazing. There were a lot of external works included within the overall contract sum, and while I have discounted these, it is entirely likely the contractor made allowance for these works within the other prices and then post-rationalised the external works price out. Again, I would like to stress that there is no real science in the above, and floor area based estimations are a pretty blunt tool. When considering an area based estimation, don’t forget to add in the VAT, or to allow for all of the aspects we have discounted.

NOTE: This article was originally written in 2020 with projects completed prior to then. Since then, there have been significant financial pressures on construction so for domestic extensions we are generally advising that a square metre rate of upwards of £2500+VAT/m2 should be used as a starting point. [October 2022]