Adding an outbuilding can be an effective way to create extra space without making major changes to the main house. Whether you are considering a garden office, gym, workshop, studio, garage, storage building, or another type of garden structure, understanding the planning position should be one of the first steps.
The key question for many homeowners is whether an outbuilding requires planning permission or can be built under permitted development rights.
The answer depends on several factors, including the building’s size and height, its position, how much of the garden is already covered by buildings, and the intended use of the structure.
This guide explains the main planning considerations to help you understand when planning permission may be required and what to consider before starting work.
What Is an Outbuilding?
An outbuilding is a separate structure located within the grounds of a residential property.
Common examples include:
An outbuilding can serve a variety of purposes, but its intended use can have an important bearing on the planning position.
A building used as a workshop or storage space may be treated differently from a building designed to provide independent residential accommodation.
For this reason, planning permission should not be assessed based on the size of the structure alone. The proposed use, location and relationship with the main dwelling should also be considered.
Do You Need Planning Permission for an Outbuilding?
Not every outbuilding requires a planning application.
Some outbuildings can fall within permitted development rights where the relevant requirements are satisfied. This can allow certain garden buildings to be constructed without submitting a full planning application.
However, permitted development is subject to specific limitations.
For example, there are restrictions relating to:
If the proposal does not satisfy the applicable requirements, planning permission for an outbuilding may be necessary.
It is therefore important to assess the complete proposal rather than assuming that every garden building is automatically permitted.
When Is Planning Permission for an Outbuilding Required?
Planning permission may be required when an outbuilding falls outside the relevant permitted development limitations.
This can happen for a number of reasons.
For example, a proposed building may be too high, positioned in an unsuitable location or occupy too much of the available garden area.
Planning permission may also be required where the building is intended to provide independent accommodation rather than being used for a purpose incidental to the main dwelling.
The circumstances of each property are different, so the fact that a neighbour has constructed a similar building does not necessarily mean that the same proposal can be built at your property without permission.
Outbuilding Height and Boundary Restrictions
Height is one of the most important considerations when planning an outbuilding.
An outbuilding covered by permitted development rights must generally be single storey. There are also limits on the maximum eaves height and overall height.
For a building with a dual-pitched roof, the maximum overall height can generally be up to 4 metres, while other roof designs are generally subject to a maximum overall height of 3 metres.
The eaves height is generally limited to 2.5 metres.
There is also an additional restriction where the proposed building is within 2 metres of the boundary. In these circumstances, the overall height is generally limited to 2.5 metres.
These measurements can have a significant effect on the design of a garden room, office or workshop.
For example, a homeowner may have enough space in the garden for a proposed building but find that the preferred roof design cannot be accommodated within the applicable height restrictions.
Planning the dimensions carefully from the beginning can therefore help avoid unnecessary changes later.
Where Can an Outbuilding Be Positioned?
The location of an outbuilding within the property is another important planning consideration.
An outbuilding cannot generally be positioned on land forward of a wall forming the principal elevation of the original house where permitted development rights are being relied upon.
The relationship between the outbuilding and the main house should therefore be considered before deciding where the structure will be located.
Other factors may also be relevant, including:
A proposal that appears acceptable when viewed in isolation may need to be reconsidered once its position within the wider property is taken into account.
How Much of the Garden Can Be Covered?
The amount of land already occupied by buildings can affect whether an outbuilding falls within permitted development.
Generally, no more than half of the land around the original house can be covered by additions or other buildings under the relevant permitted development rules.
This means that the calculation is not simply based on the size of the new outbuilding.
Existing extensions and other buildings may also need to be considered.
This can become particularly important where a property has already been extended or where there are existing garages, sheds, garden rooms or other structures.
Before finalising the size of a proposed outbuilding, it is therefore sensible to establish how much of the relevant land is already covered.
Does the Use of the Outbuilding Matter?
Yes. The proposed use can be an important part of determining whether planning permission is required.
Outbuildings can generally be used for purposes that are incidental to the enjoyment of the main dwelling.
This can include uses such as:
However, an outbuilding intended to function as an independent home can raise different planning considerations.
The planning authority may consider how the building is designed and how it is intended to operate rather than relying solely on the description given to it.
For example, a building containing sleeping accommodation, a kitchen, bathroom and other facilities that allow independent occupation may be treated differently from a simple garden office.
Can You Build a Garden Office Without Planning Permission?
A garden office can potentially fall within permitted development rights if the relevant requirements are satisfied.
However, the fact that a building is described as a “garden office” does not automatically mean that planning permission is unnecessary.
The dimensions, location, height and other characteristics still need to comply with the applicable requirements.
The proposed office should also remain ancillary to the main dwelling.
If the intention is to create a separate unit that can be occupied independently, the planning position may be different.
Homeowners considering a garden office should therefore establish the planning position before ordering materials or starting construction.
Can an Outbuilding Be Used as a Bedroom or Annexe?
This is an area where particular care is needed.
An outbuilding intended to provide independent residential accommodation may not fall within the permitted development rights that apply to ordinary ancillary garden buildings.
For example, a structure designed to operate as a self-contained annexe with sleeping accommodation, kitchen and bathroom facilities can raise additional planning considerations.
The question is not simply whether the building is located in the garden. Its function and relationship with the main dwelling are also relevant.
If your intention is to create accommodation for a family member, guest or other occupant, it is advisable to establish whether planning permission is required before construction begins.
What About Flats and Maisonettes?
The permitted development rights applicable to outbuildings are generally associated with houses.
Flats and maisonettes do not benefit from the same householder permitted development allowances. This means that an owner or occupier of a flat or maisonette should not assume that the rules applying to a house with a private garden will also apply to their property.
The ownership and use of the surrounding land may also need to be considered.
If you live in a flat or maisonette and are considering a garden structure, professional advice can help establish the relevant planning position before work begins.
What If the Property Is Listed?
Listed properties require additional consideration when planning an outbuilding.
The planning restrictions affecting listed buildings can mean that an outbuilding cannot simply rely on the same permitted development position as an ordinary house.
An outbuilding within the curtilage of a listed building may require planning permission.
There may also be separate heritage considerations depending on the property and the proposed works. If your property is listed, the planning position should therefore be checked before you finalise the design of an outbuilding.
What If the Property Is in a Designated Area?
Certain properties can be subject to additional planning restrictions because of their location or designation.
This can affect the extent to which permitted development rights can be used.
For example, additional restrictions can apply to outbuildings in certain protected or designated locations.
The position should therefore be assessed based on the specific property rather than relying solely on standard permitted development measurements.
Can You Build an Outbuilding Without a Planning Application?
Where all the applicable permitted development requirements are satisfied, a planning application may not be necessary.
However, homeowners often want greater certainty before committing to construction.
One option may be to obtain a Lawful Development Certificate where the proposed development is considered lawful under the relevant planning rules.
This can provide formal confirmation of the planning position and can be useful when selling the property or dealing with future planning matters.
A certificate is not automatically required for every permitted development project, but it can provide useful evidence of the development’s planning status.
What Happens If You Build Without Planning Permission?
Starting construction without first checking the planning position can create problems if the development later turns out to require permission.
If the local planning authority determines that planning permission was required, the homeowner may need to consider a retrospective application or other steps to address the planning issue.
Depending on the circumstances, enforcement action may also be possible.
If retrospective permission is refused, changes to the building or removal of the development could potentially be required.
This is why checking the planning position before construction is generally preferable to dealing with a planning problem after the building has been completed.
Does an Outbuilding Need Building Regulations Approval?
Planning permission and building regulations are separate matters.
An outbuilding may not require planning permission but could still be subject to building regulations depending on its size, construction and intended use.
This is particularly relevant where the structure is intended to be used regularly as an office, accommodation or another form of occupied space.
The structural design, insulation, foundations, electrical installations and other aspects of construction may need to be considered separately from the planning position.
Homeowners should therefore consider both planning and building control requirements before beginning construction.
What Should You Check Before Building an Outbuilding?
Before starting work, it is sensible to review the proposal carefully.
Check the Proposed Dimensions
Measure the proposed height, eaves height, width and depth.
Even relatively small changes can affect whether the building remains within the applicable permitted development limits.
Check the Boundary Distance
Establish exactly how far the proposed structure will be from the relevant boundaries.
This can affect the maximum permitted height.
Check Existing Buildings
Consider existing extensions, garages, sheds and other structures when assessing the amount of land already covered.
Check the Intended Use
Be clear about how the outbuilding will actually be used.
A storage building, office, workshop and independent accommodation can raise different planning questions.
Check the Property Restrictions
Consider whether the property is listed, located within a designated area or subject to other planning restrictions.
Review the Planning History
Previous applications, permissions and development at the property may affect the current proposal.
Understanding what has already been approved or built can help establish the planning position before work begins.
Why Get Planning Advice Before Building?
Outbuilding projects can appear straightforward, but planning rules can become complicated when several factors apply at the same time.
A planning consultant can assess the proposal and help you understand whether planning permission is required.
This can include reviewing:
Early advice can also allow potential issues to be identified while the design can still be changed.
Rather than designing and constructing an outbuilding first and addressing planning issues afterwards, obtaining advice at the beginning can provide greater clarity about the appropriate route.
How a Planning Consultant Can Help With an Outbuilding
A planning consultant can provide advice at different stages of an outbuilding project.
The initial assessment may establish whether the proposal could benefit from permitted development rights or whether a planning application is likely to be required.
Where planning permission is needed, a consultant can also help with the planning strategy and application process.
This may involve:
At Expert Planning Consultants, we provide professional planning advice for homeowners and property owners considering a wide range of development projects.
For additional information about how professional planning advice can help with different types of property projects, see our related article, Planning Permission Consultant: What You Need to Know.
Frequently Asked Questions About Planning Permission for Outbuildings
Do I always need planning permission for an outbuilding?
No. Some outbuildings can be built under permitted development rights if all the relevant requirements are satisfied. However, planning permission may be required if the proposal exceeds the applicable limitations or other restrictions apply.
How tall can an outbuilding be?
The permitted height depends on the roof design and its distance from the boundary. Different maximum heights can apply depending on these factors, so the proposed dimensions should be checked carefully before construction.
Can I build an outbuilding next to my boundary?
An outbuilding can potentially be positioned close to a boundary, but additional height restrictions can apply where the structure is within 2 metres of the boundary.
Can I use my outbuilding as a home office?
A garden office can potentially be permitted development where all the relevant requirements are satisfied, and the use remains ancillary to the main dwelling.
Can I use an outbuilding as accommodation?
An outbuilding intended to provide independent residential accommodation can raise different planning considerations. If it is designed as a separate living unit, planning permission may be required.
Can I build an outbuilding if I live in a flat?
The permitted development rights that apply to houses do not generally apply to flats and maisonettes in the same way. The planning position should therefore be checked before proceeding.
Can I get permission for an outbuilding after it has been built?
It may be possible to make a retrospective planning application, depending on the circumstances. However, it is preferable to establish whether permission is required before construction begins.
Should I apply for a Lawful Development Certificate?
A Lawful Development Certificate can provide formal confirmation that a proposed or existing development is lawful in planning terms. Whether one is appropriate will depend on the circumstances of the project.
Planning Permission for Outbuilding
Understanding planning permission for an outbuilding before construction begins can help you avoid unnecessary planning problems later. Although some garden buildings can fall within permitted development rights, this depends on meeting the relevant requirements relating to matters such as height, position, boundary distance, garden coverage and intended use.
The planning position can also be affected by the type of property, existing development, planning history and any restrictions affecting the site. An outbuilding used as a garden office or workshop may have a different planning position from one intended to provide independent accommodation.
At Expert Planning Consultants, we can assess your proposed outbuilding and provide professional planning advice based on your property’s circumstances and your intended use.
Contact us today to discuss your outbuilding proposal and find out how our planning consultants can help you move your project forward. If you are considering an outbuilding and are unsure whether planning permission is required, obtaining professional advice at an early stage can help clarify the position and identify the appropriate route forward.