Extension Without Planning Permission: A Complete Guide

What size extension can i build without planning permission

by | Jul 26, 2023 | House Extension, Home Refurbishment | 0 comments

Building extensions to your property can be an exciting prospect, offering additional living space, increased functionality, and potential value appreciation. However, the process of obtaining planning permission can be time-consuming and costly. 

Luckily, in the UK, there are certain types of extensions that can be built without the need for planning permission, thanks to Permitted Development Rights (PD). 

In this article, we will explore the various types of extension without planning permission, the restrictions and limitations that apply, and the benefits of opting for this route.

Permitted Development Rights (PD)

Permitted Development Rights are a set of rules and guidelines that allow homeowners to carry out certain alterations and extensions to their properties without the need to obtain planning permission.

These rights are granted by the General Permitted Development Order (GPDO) and are subject to specific limitations and conditions. One of the significant advantages of PD is that it grants homeowners greater flexibility and freedom to make improvements to their homes.

Under PD, several types of extensions and alterations can be undertaken without seeking planning permission from the local authority. 

What Size Extension Can I Build Without Planning Permission

Here are some key size limitations to consider:

Single-Story Rear Extensions

For single-story rear extensions, the height must not exceed 4 metres, and the extension must not extend beyond 3 metres from the original rear wall of the property. If your property is located in designated land, such as conservation areas or areas of outstanding natural beauty, the maximum height reduces to 3 metres, and the extension cannot extend more than 3 metres from the original rear wall.

Two-Story Rear Extensions

You can build a two-story rear extension without planning permission, but there are stricter rules. The extension cannot be closer than 7 metres to the rear boundary, and the eaves and ridge height must not exceed that of the existing house.

Loft Conversions

Converting the loft into habitable rooms, such as bedrooms or home offices, can also be done under permitted development. However, the additional volume created by the conversion must not exceed 40 cubic metres for terraced houses or 50 cubic metres for detached and semi-detached houses. Additionally, the loft conversion should not extend higher than the highest part of the existing roof.


Outbuildings, such as garden sheds, garages, and summerhouses, can be constructed without planning permission, subject to certain size restrictions. The maximum height for outbuildings with dual-pitched roofs is 4 metres, and for other roof types, it is 3 metres. The maximum eaves height is limited to 2.5 metres.

Other Considerations

When planning an extension without seeking planning permission, it’s crucial to keep in mind the following:

Total Land Coverage

The extension, along with any other buildings and structures (including the main house), must not cover more than 50% of the total land area around the original property.

Conservation Areas and Designated Land

If your property is located in a conservation area or designated land, additional restrictions may apply. It’s important to consult with the local planning authority to ensure compliance with any specific guidelines or conservation requirements.

Permitted Development Allowances

Permitted development allowances can vary depending on the local planning authority and the specific area where your property is located. Therefore, it’s advisable to seek professional advice or check with your local authority to confirm the exact permitted development rights applicable to your property.

Consequences of Building Without Planning Permission in the UK

So, what happens if you build without planning permission? Building without planning permission in the UK can have significant legal and financial consequences.  

When a property owner or developer fails to obtain planning permission before carrying out construction, they are in breach of planning regulations, leading to various consequences:

Enforcement Action

Local planning authorities have the power to take enforcement action against unauthorised development. This typically involves issuing an enforcement notice to the property owner, demanding that the unauthorised construction be halted and, in some cases, reversed or modified to comply with planning rules. The enforcement notice may set out a deadline for compliance, and failure to comply can result in further legal action.

Demolition Orders

In extreme cases, where the unauthorised development has caused significant harm to the local environment or the property’s surroundings, the local planning authority may issue a demolition order. This would require the property owner to demolish the unauthorised structure entirely at their own expense.

Fines and Prosecution

The property owner can face fines and penalties for building extension without planning permission. The local planning authority can take legal action against the owner, and if found guilty, they may be liable for substantial fines. Repeat offenders may face more severe penalties.

Difficulty Selling the Property

Unplanned or unauthorised construction can create issues when selling the property. Prospective buyers may be hesitant to purchase a property with unauthorised development due to the potential legal complications and the risk of enforcement action being taken against them in the future.

Property Devaluation

Unauthorised development can negatively impact the value of the property. The presence of an unauthorised structure can deter potential buyers and may result in the property being devalued compared to similar properties with appropriate planning permission.

Refusal of Future Planning Applications

Building extension without planning permission can also affect the property owner’s chances of obtaining planning permission for future development. Local planning authorities may be less likely to grant permission for future projects if the owner has a history of non-compliance with planning regulations.

Loss of Time and Money

If enforcement action is taken, the property owner will not only have to bear the cost of demolishing or modifying the unauthorised development but may also face legal fees and expenses associated with the enforcement process.

How Much Can You Extend Without Planning Permission?

The question is “how much can you extend without planning permission?” Here are some general guidelines for extension without planning permission:

Single-Story Rear Extensions

For single-story rear extensions, the maximum depth (distance from the original rear wall of the house) is generally limited to 3 metres for terraced and semi-detached houses, and 4 metres for detached houses. In some cases, these limits may be increased to 6 metres and 8 metres, respectively, if prior approval is obtained from the local planning authority.

Two-Story Rear Extensions

Two-story rear extensions are subject to stricter limitations. They must not be closer than 7 metres to the rear boundary, and the eaves and ridge height of the extension must not exceed the existing house’s highest point.

Loft Conversions

Loft conversions can often be carried out without planning permission under permitted development, subject to certain restrictions. The volume created by the conversion must not exceed 40 cubic metres for terraced houses and 50 cubic metres for detached and semi-detached houses. Additionally, any dormer extensions must not extend beyond the plane of the existing roof slope at the front of the house.


Outbuildings, such as garden sheds, garages, and summerhouses, can be constructed without planning permission, provided they adhere to specific size restrictions. The maximum height for outbuildings with dual-pitched roofs is 4 metres, and for other roof types, it is 3 metres. The maximum eaves height is limited to 2.5 metres.

Front Porches

Front porches can be added to a property without planning permission, provided they meet certain size and placement requirements. Generally, a porch should not exceed 3 metres in height and must not have a floor area larger than 3 square metres. The porch should be at least 2 metres away from any highway boundary.

What Can I Build On Agricultural Land Without Planning Permission?

Majority of the time, the question revolves around “what can I build on agricultural land without planning permission?”

Agricultural land also has specific rules and regulations regarding the construction of buildings and structures. While some agricultural buildings without planning permission may be exempt from planning permission, others may require prior approval or permission from the local authority. 

These rules often consider factors such as the size, use, and location of the proposed agricultural building.

Benefits Of Extension Without Planning Permission

Extending your property without the need for planning permission offers several benefits, making it an attractive option for homeowners in the UK. Here are some of the key advantages of extending without planning permission:

Time and Cost Savings

Obtaining planning permission can be a time-consuming and costly process. By extending under permitted development rights, homeowners can save time on navigating through the planning application process and avoid the associated fees.

Faster Project Completion

Without the need for planning permission, the extension project can be initiated and completed more quickly. This allows homeowners to enjoy their new living space sooner, which is especially beneficial for those with time-sensitive needs, such as growing families or work-from-home requirements.

Flexibility in Design

Permitted development rights often offer homeowners greater flexibility in the design of their extensions. As long as the project adheres to the permitted development guidelines, homeowners can have more freedom in shaping the extension to suit their preferences and needs.

Improved Property Value

A well-designed and properly executed extension can significantly enhance the value of the property. With the ability to extend under permitted development, homeowners can invest in their homes with confidence, knowing that their improvements are compliant and likely to add value to the property.

Increased Living Space

One of the primary reasons for extending is to gain additional living space. Permitted development rights enable homeowners to achieve this goal efficiently and without delays.


In conclusion, building extensions without planning permission in the UK is possible under certain conditions. Permitted Development Rights provide homeowners with the opportunity to expand their properties within specific limitations and criteria. 

By adhering to these guidelines and seeking professional advice when necessary, homeowners can successfully extend their properties and enjoy the benefits of additional space and improved functionality. 

Always remember to consider any local rules and conservation area restrictions to ensure compliance and avoid potential legal consequences.


What size garden room without planning permission?

Generally, a garden room can be up to 15-30 square metres in size without requiring planning permission, subject to specific conditions and restrictions.

How big can a porch be without planning permission uk?

A porch can typically be up to 3 metres in height and have a floor area no larger than 3 square metres without needing planning permission, as long as it meets other placement requirements.

Emmanuel Nwaebo

Emmanuel Nwaebo is the Managing Director at Powerpillar Ltd and has more than 25 years experience in building construction and renovations. He has a bachelor’s in Electronics and Electrical Engineering with certification in Construction Health and Safety Technician (CHST). With an experience in managing construction and renovation services for years, he is extremely passionate about property management and loves helping people find their dream property.

Get Your Quote Now


Powerpillar offers customised solutions tailored to meet the individual style preferences of its clients.

The Top 5 Benefits of Choosing a Custom Home Builder

Purchasing a home is usually one of the biggest investments for many people. There are two options when buying a new home for yourself and family. One is to buy a pre-built home, and the other is to purchase custom built house. Choose a custom home as it has many...

How a 3 Metre House Extension Creates Your Dream Cooking Space

Adding more living space to your home and increasing its value is a popular choice, and a home extension is a great way to accomplish this goal. Who wouldn't want more room to enjoy?  Are you tired of adjusting to a cramped kitchen, dreaming of a space where you can...

Top Bathroom Tile Trends in the UK for 2023

As we enter a new era of interior design, the bathroom serves as a blank canvas for expression and creativity. In the area of bathroom floor tiles, the United Kingdom experienced a stunning combination of classic beauty and nostalgic charm in 2023. This year's trends...

Integral Garage Conversion – An Ultimate Design and Cost Guide

Ever looked at your garage and thought, "Man, there should be a better use for this space?" Well, you are not alone. You have this integral garage, probably housing more dust than anything else. But hold on, there's a cool solution. You can go for an integral garage...

7 Brilliant Benefits of Glass House Extensions

Imagine sitting at a table, finding inspiration to write a new song, and amid the struggle, a bird flies by and gives you thousands of words. Imagine being a nature lover and wanting to spend time outdoors without going out. It might seem delusional at first, but let...

Under Garden Basement

Are you dreaming of expanding your living space without sacrificing your beautiful garden? Well, we have some exciting news for you! You can now build an under garden basement extension right under your garden! In this article, we'll walk you through the entire...

Basement Conversions in London

A basement conversion is a process of transforming the often-underutilised space beneath your property into a functional and habitable area.  This step-by-step guide explores the advantages of basement conversions, how to build a basement, all tailored to adhere to...

A Step-by-Step Guide to Section 80 Demolition Notice

If you own a property or are involved in property development, being aware of the Section 80 Demolition Notice is crucial. This notice holds significant importance as it directly affects the demolition of structures and carries legal implications.  In this article, we...