A Complete Guide to Home Extensions

The Benefits of Extending


Extending your home can really make a difference in the way you live and enjoy your space. Whether it’s adding an extra bedroom for a growing family or having a larger kitchen, there are many benefits:

  • More natural light
  • More space
  • Keeping your home and not moving to a different location
  • Permitted development
  • Adding value to your property.

Building an extension not only improves your living space but adds significant value. Within London, a small 15m2 extension could increase the value of a house by an added £60,000. The important factors that affect the value rate are size, location and quality.

Why not check out the added value of your house with an extension on the following link:

Calculator – Will an extension increase the value of my house? 

Getting Started


Firstly, you need to secure planning permission; whether that be by seeking approval from your local council or benefitting from permitted development rights.

In simple terms, planning permission is seeking approval to do building works. Parliament has given your Council the power to assess particular proposed works against a national and local framework. Parliament has also passed Legislation which allows you to do some types of works without seeking planning permission from your local Council; permitted development.

So whether you need planning permission or not depends on what you’re proposing, and your local council.

 

Permitted Development

There are a number of types of home extensions/improvements you can do without planning permission, as long as they follow the guidelines. 

As an example, here are some of the conditions for erecting a single-storey rear extension:

  • extend beyond the rear wall of the original house by more than 4 metres in the case of a detached house, or 3 metres in the case of any other house. (under prior approval 8 metres in the case of a detached house, or 6 metres in the case of any other house)
  • exceed 4 metres in height.
  • the total area of ground covered by extension would exceed 50% of the total area of the curtilage of the original house.

As you can see, it can be quite complicated however with a planning expert it’s a breeze. It’s important to employ a competent planner, rather than an architect, as they have expertise and knowledge to understand and apply to the council. 

Non-compliance to the conditions could lead to intervention from planning enforcement which may result in having to apply for planning permission to the Council, or in the worst-case scenario carrying out further works to comply. To avoid all this, stick to a planning expert.

Can I benefit from Permitted Development rights?

This all depends on your property and your local council. If you own a house, not a flat or maisonette, then you could benefit from this right. You would need to check with your local council to see whether these rights apply within your area as some councils remove this right so that you formally apply for planning permission. A planning expert can help navigate through this and confirm whether your proposal fits within the rights.

Do I need to apply for Permitted Development?

Technically, no. The permitted development right for extensions is planning permission subject to conditions and limitations. You could crack with your extension as soon as you have confirmation from your planning expert.

However, it is recommended to apply for a Certificate of Lawfulness prior to the commencement of building the extension. The Certificate is a formal document from the local council confirming that the extension complies with permitted development and therefore it is lawful. It is a legal document and can provide to be essential when selling the property as the buyer’s solicitors may request this as proof. In addition, it is worth getting this approval as permitted development rights are amended by Parliament as and when deemed necessary.

Compliance & Regulations


Applying for a Certificate of Lawfulness

If you do apply for a Certificate of Lawfulness, then you would need to provide the following:

  • The application form
  • Architectural drawing plans (Elevations, Floor and Location Plans)
  • A fee 

The application form can be found on the local council’s website or you can apply via Planning Portal. A planning expert can manage the whole process with you liaising with an architect. Once the application is validated by the council, it could take around 8 weeks for a determination. 

Unlike a normal planning application, the council cannot refuse the Certificate if it complies with the permitted development requirements.

It’s important to employ a competent planner, rather than an architect, as they have expertise and knowledge to understand and apply to the council. 

Applying for Planning Permission

If you wish to build an extension that goes beyond the permitted development rights, then you would need to apply for planning permission to the local council. 

Submitting an application needs to meet validation requirements set by national and local standards. The essential document would be similar to a Certificate of Lawfulness, however, you may need to submit further documents:

Essential:

  • Application Form
  • Architectural Drawing Plans (Elevations, Floor and Location Plans)
  • A Fee 

Other:

  • Design And Access Statement
  • Tree Report
  • Ecology Report
  • Flood Risk Assessment

Each council has its own specific list and therefore you may need to submit other documents to comply with validation requirements. 

Once the application has been validated, it is allocated to a planning officer to assess the proposal. The application is assessed against national and local planning policies taking into a number of considerations such as:

  • Design and Appearance
  • Character
  • Neighbour Impact
  • Local Constraints

It is therefore paramount that the application is considerate, aiming to enhance and complement the house and local area. 

A decision of the application would be issued usually by a minimum of 8 weeks. During the assessment the planning officer may discuss the application with you, however, they are not obliged to do so. Sometimes if it’s a tweak that would be more preferable for the council then it can be addressed by the architect. 

What happens if my application gets refused?

If your application is refused, there are two options you could take to secure planning permission. 

  1. Re-apply 
  2. Appeal

Your planning agent will be able to decipher the decision by the council and advise whether it is worthwhile submitting a revised scheme or appealing. 

Sometimes a refusal can simply be fixed by making an amendment and submitting a revised application. It doesn’t cost to re-submit, as long as it’s done within 12 months of the refusal. The only cost you may need to consider is for the architect to make these amendments and for the planning agent to re-submit, which shouldn’t cost much.

If an appeal is required, then this can be a lengthy process but sometimes prove to be worth it. It is advisable to use a planning expert to manage the process as it can be complicated and lengthy. You would need to submit an appeal to the Planning Inspectorate, an independent body to the local council, with an accompanying appeal statement and any required documents. 

Once planning permission has been granted, you then will need to proceed to get detailed drawings for compliance with building regulations, and for builders to use.

Building Control

As part of the building process, you need to comply with Building Regulations. 

Buildings are controlled by The Building Regulations which ensures that they are going to be built safe, healthy and high-performing. The regulations cover specific topics: structural integrity, fire protection, accessibility, energy performance, acoustic performance, protection against falls, electrical and gas safety. They also lay standards for drains, ventilation, protection against the ingress of water and protection against contamination including methane and radon gas. 

You would need to submit an application to the Council with drawing plans demonstrating compliance. A structural engineer will need to complete a survey and share their expertise with the architect to ensure the plans are correct.

The expected cost for the whole process would be similar to applying for planning permission.

The Build


The cost of a home extension will depend entirely on the:

  • Size of Extension
  • Location 
  • Structural Layout
  • Glazing

An important factor to consider could be where the extension affects a neighbouring party wall. A Party Wall Agreement would need to be drafted up where you may need to employ a party wall surveyor, which factors both yours and the parties costs.

You should ensure all the following items are clarified before agreeing with a builder to carry out your extension works:

  1. Detailed Quotation
  2. Building Schedule (Itemised and Costs)
  3. Project Management (Management of Build, Timescale, Quality Assurance)
  4. Considerate Builders Plan (Minimise disruption to yourself and neighbours, Routine Site Clearance, Protect House)
  5. Full Liability Insurance
  6. Payment Terms 
  7. Skip Hire
  8. Other Costs 

Summary


Here is a step by step breakdown of getting your extension completed:

Phase 1

  • Discussion with Planning Officer
  • Survey by Architect
  • Drawing plans
  • Obtain specialist reports
  • Submission of application

Phase 2

  • Meeting with Builder
  • Schedule of works and costs
  • Draw and prep plans for application 
  • Stages of inspection Agreement
  • Commencement of building works
  • Survey from Building Inspector
  • Completion Certificate

We hope this guide has given you insight into the process, the expected costs and some key details of compliance and regulations. For more expert advice or support with your planning application please get in touch. 


Building Process to Single Storey Rear Extension

1. Site Preparation

The first stage of the building process is preparing the site so we can work efficiently. The area of where building works will be carried out and the access routes are cleared from any rubbish. The materials and equipment required to do the initial works are cleverly planned out and located at the builder’s convenience. The site is protected and made safe.

2. Groundworks

The foundation of the building is where the quality of the build starts. The foundations are dug out per building regulation specifications which ensure it is structurally sound and legal. The Building Control inspector will check the depth and width, and advise or sign off this part so that the footings can be poured. If required, reinforcement and drainage systems will be inserted into the foundations. Thereafter, the concrete is poured into the foundation to create a solid footing. The Building Control inspector will visit again to approve the footing.

3. Superstructure

The bricks are laid to build up the damp-proofing course. Sand is laid before the damp-proofing membrane, and insulation is fitted. To finish off the flooring, the concrete slab is poured and levelled. The Building Control inspector will complete a visit and check the works.

4. External and Internal Walls

The blockwork and brickwork are created and cavity wall insulation is fitted within. Wall ties will be fitted to the new walls and existing walls of the house. The lintels and frames for the doors and windows are fitted. Any internal walls within the extension will be built.

5. Roof

The roof structure is formed. The roof battens are cut and fitted over the membrane. The slates or roof tiles are laid, ridge and valley tiles are fitted. The fascias, soffits and verges finish off the roof appearance making it secure and complete. The floor screed is poured to make the ground durable and soft for additional floorings such as carpet or wood.

6. Windows and doors

The windows and door are fitted in the frames. The guttering and drainpipes are fitted by the roof and external flank elevations.

The foundation of the building is where the quality of the build starts

7. First Fix

A practice known as first-fix is completed ensuring all the electrics, plumbing and carpentry are in place. The studwork wall is fitted with door linings and pipes are boxed in.

8. Demolition

To allow access from the rear wall of the house to the extension and connect the buildings, steels are fitted along with padstones.

9. Plastering

The battens placed internally forming the walls will be insulated and boarded. The plastering will be completed and left to dry for approximately one week.

10. Painting

Once the plastering has completely dried, the walls and ceilings will be painted.

11. Second Fix

The electrics will be wired, and switches and lights will be fitted. The sockets will be made live. The plumbing will be completed with taps in place and connections installed. The flooring will be laid and finished off.

12. Completion

Any finishing fittings and touches are completed. The works are completed and a completion certificate will be provided by Building Control

Once all the building works have been completed and signed off, it’s important to ensure you have all the relevant documents stored safely and accessible when required. In the event where you may wish to sell your property, solicitors require the documents provided by the council and building control to demonstrate the build is lawful and in compliance with regulations.


Can I extend up to 6 metres without planning permission?

Planning Permission

You can build a large single storey rear extension without applying for planning permission to your local council (Larger Home Extension Scheme).

Under permitted development, you can extend up to 8 metres (detached house), or 6 metres (other than a detached house), subject to conditions set out in Class A, Part 1, Schedule 2 of The Town and Country Planning (General Permitted Development) (England) Order 2015.

This right was for a limited time only, however it has now been made available with no time limit.

You can build a large single storey rear extension without applying for planning permission...

Prior Approval Notification (neighbour consultation scheme)

To take advantage of this, you would need to go through a process known as prior approval notification (neighbour consultation scheme), which informs the council that you wish to build a large extension. The council will then notify neighbours of the scheme, and if the neighbours comment, a view will be taken of whether there is any impact on the amenity of the neighbouring properties.

With experts involved, you don’t have to stress about getting your head around all the details and the planning jargon, as they will know the conditions and requirements set out for this process. It’s worth investing in doing it properly from the outset rather than stumbling on difficulties during the build which could lead to enforcement action.


Do I need Planning Permission for my flat or maisonette?

Maisonette and Flat

A flat is a dwelling place which usually comprises several rooms on one floor, within a building that has a shared entrance. 

A maisonette is similar to a flat, usually within a house but has its own private entrance and can be more than one floor.

Planning Permission

There are rights within the planning legislation that permits certain types of works or uses subject to conditions.

The Town and Country Planning (General Permitted Development) (England) Order 2015, Part 1, Schedule 2 permits enlargement, improvement or other alteration to a dwellinghouse without planning permission. 

Flats and maisonettes do not benefit from permitted development rights. 

Although there is no clear particular reason why there is a difference, one of the reasons could be that Parliament wants Local Authorities to have extra control over what can be developed for flats and maisonettes, as they may perceive them to differ from normal standard houses where there could be more flexibility for home improvements and where the impact of the proposed development could be acceptable in terms of planning.

Party Wall

Living in a flat or maisonette usually comprises sharing a wall with a neighbour. In such instances, a party wall agreement may need to be completed with your neighbours. This is to enable owners to carry out works whilst protecting their neighbours and avoiding necessary inconveniences and avoid disputes in advance of proposed works. 

Leasehold

It is common that a flat and maisonette may be under leasehold ownership. If so, it would usually require consent from the freeholder to carry out any work to the building.

Flats and maisonettes do not benefit from permitted development rights. 

Pre-Assessment

Although you can’t do building works to your flat or maisonette under permitted development, you can still obtain planning permission. To check the likeness of whether planning permission would be approved, you can complete a pre-assessment before investing in submitting an application to the council. To get an initial free quote in less than two minutes, please click the ‘Get a Quote’ icon and follow the steps.


Do I need Planning Permission?

What is Planning Permission?

Planning permission is seeking authorisation to do particular building works, or change the use of the building/land.

Parliament has given local councils the power to assess particular proposed works against a national and local framework.

Parliament has also passed Legislation which allows you to do some types of works without seeking planning permission from your local council; known as ‘permitted development’. If a formal determination is required for permitted development works from the council, then you would need to apply for a Certificate of Lawfulness which is similar to the requirements of submitting a normal planning application.

How do I apply?

You will need to submit a planning application which meets the validation requirements set by national and local standards. The application will need to include the following:

Required:

  • Application Form
  • Architectural Drawing Plans (Elevations, Floor and Location Plans)
  • A Fee

Possibly Required:

  • Design And Access Statement
  • Tree Report
  • Ecology Report
  • Flood Risk Assessment

Each council has its own specific list and therefore you may need to submit other specialist reports to comply with validation requirements. Appointing an expert in planning to manage the process is the best and safest way to ensure you’re getting the best out of what you want to apply for and ensuring compliance with the set requirements.

Planning permission is seeking authorisation to do particular building works, or change the use of the building/land.

How long does it take?

The preparation of an application and getting it submitted to the council takes around 2 weeks. The application is considered by a planning officer at the council and thereafter a decision is issued within 6-8 weeks.

Our process:

  • Pre-Assessment – Planner
  • Survey – Architect/Designer 
  • Drawing Plans (Elevations, Floor, Location, Site etc) – Architect/Designer 
  • Obtain Reports, if required – 3rd Party Specialist 
  • Submission of Application – Planner

So whether you need planning permission or not depends on what you’re proposing. With our team of experts, we can help and manage it all for you. To get an initial quote, get in touch now and find out within less than two minutes!


Loft Conversion

An assessment will need to take place to see if the loft is suitable for a conversion. Our architect will look at the height, roof pitch, and footprint of the roof area. Based on the dimensions, the architect will design and draw out proposed floor plans and elevations to visualise how the room can be used, whether being a bedroom with en-suite or an alternative room for the house such as an office, playroom etc. 

 

Loft Conversion Types

There are a few ways to maximise the space within the loft and get the most of natural light. Here are some of the ways you can do this:

  • Roof Light
  • Single Dormer
  • Full Width Dormer
  • Side Dormer
  • Hip-to-Gable
  • L-Shape Dormer
  • Mansard 
  • Pre Fabricated 

 

Planning Permission

A loft conversion itself does not require planning permission, unless there is a restrictive historic condition preventing such conversions without applying to the local council. As with all our projects, we carry out a pre-assessment to check the planning history and compliance with planning control.

If the loft conversion alters the roof form in any shape, then this would be considered ‘development’ and therefore is subject to planning control. Under permitted development, you can erect dormers and roof lights to the loft conversion subject to limitations. The planning expert and architect will work together to bring about the best possible way to convert the loft per permitted development rights.

Although planning permission may not be required, it is advisable to obtain a Certificate of Lawfulness, which is a formal document from the council stating that it is permitted development.  This can play an essential piece of the puzzle when you’re trying to sell the house as Solicitors will carry out checks to see if everything has been built lawfully.

Although planning permission may not be required, it is advisable to obtain a Certificate of Lawfulness

Building Regulations

Apart from planning, the loft conversion is subject to approval from Building Control. The architect and structural engineer will look at the build of the conversion checking the structural strength, the stability of the new loft, fire escape, stairs to the loft, and insulation.

 

Party Wall

A party wall agreement may be required where your house is semi-detached or terraced as the loft will adjoin a neighbouring property. The agreement can cost around £1,000, however if you are able to get your neighbour to sign a waiver, you may be able to alleviate this cost. 

 

Costs

The cost of the loft conversion is based on the room type, design and materials. To complete the assessment and design of the proposed loft conversion it usually costs around £2,000. If it requires any structural calculations or advice, then this can cost around £500.

In terms of the building works, it could cost as less as £15,000, however an average and expected rate for a typical conversion would be around £30,000 – £45,000.


Outbuilding

An outbuilding can be used in different ways:

  • Gym
  • Home Office
  • Study Room
  • Swimming Pool
  • Sauna
  • Games Room

It all depends on the intended use of the building, whether it’s used all year round, or during the warmer seasons. The use of the outbuilding will determine which materials will be required to make it suitable.

 

Types of Outbuilding

Modular – A modular outbuilding is flat packed and ready to be fitted. It can be ordered and pre-built to be assembled on site.

Bespoke – A bespoke option is where the outbuilding is designed and built according to your needs with a planner, architect and builder.

 

Planning Permission

An outbuilding can be erected under permitted development rights without the need to apply for planning permission to the local council. 

This all depends on the planning history of the property and the local council. A planning expert will carry out a pre-assessment to check whether there are any constraints restricting erecting an outbuilding. 

If there are no constraints, then it can be built without planning permission, subject to conditions and limitations. A planning expert will assess the proposed outbuilding in terms of its use and dimensions and make sure it complies with permitted development.

Bigger outbuildings and different types of uses may require planning permission. This is where a planning expert’s knowledge and experience will help you to maximise the potential of your desired outbuilding whilst complying with the local plans and policies of the area. 

Bigger outbuildings and different types of uses may require planning permission.

Building Control

Smaller outbuildings that are less than 15 square metres and propose no sleeping accommodation, then usually it doesn’t require to comply with Building Regulations.

For outbuilding bigger than 15 square metres or/and propose sleeping accommodation, then it usually requires compliance with Building Regulations. An architect will draw up detailed plans of the outbuilding providing specifications for the building inspectors to complete their assessment and approve the build.

 

Costs

The cost of the outbuilding depends on a number of factors; the use, size, materials, insulation and finishes. 

A simple shed can cost around £750, whereas a bespoke games room, which will require heating, insulation, ventilation and electricity, could cost around £15,000 – £30,000.


Garage Conversion

A garage can be converted into a number of different types of rooms. It can add value to the property by up to 20 percent. 

Here are the different ways it can be used as:

  • Gym
  • Home Office
  • Study Room
  • Bedroom 
  • Extended existing rooms such as a living room, kitchen etc.

Planning Permission

To convert a garage, it is paramount to first carry out a planning check. A planning expert will look into historic planning permission on the house which may have conditions stipulated restricting garage conversions.  

It’s common to see that many homeowners are not aware of the planning implications that a development could have, whether existing or proposed. We always carry out a pre-assessment of any site prior to commencing any building works or development. 

If the house doesn’t have any restrictive conditions, then as long as the proposed room is used in connection with the main house by its occupants for residential purposes then you may carry out the works without applying for planning permission. 

It's common to see that many homeowners are not aware of the planning implications that a development could have, whether existing or proposed.

Building Control

Although the conversion may not require planning permission, in most cases, it would be subject to Building Control’s consent. With the detailed plans provided by the architect, an application is submitted to notify the local council and building inspector of the proposed works. They will carry out an inspection of building works to ensure it complies with the regulations. They will look at the structural soundness of the building works, the damp proof course, the insulations, electrics, ventilation and fire proofing.

 

Party Wall

A party wall agreement may be required where the garage wall adjoins a neighbouring property. 

The agreement can cost around £1,000, however if you are able to get your neighbour to sign a waiver, you may be able to alleviate this cost. 

 

Costs

The cost of the garage conversion is based on the room type, design and materials. To complete the assessment and design of the proposed garage conversion it usually costs around £2,000. If it requires any structural calculations or advice, then this can cost around £500.

In terms of the building works, it could cost as less as £5,000, however as average and expected rate for a typical conversion would be around £20,000.


Porch

Porch Types

There are a few types of porches you can build:

  • Brick Porch
  • Lean to Porch
  • UPVC Porch
  • Aluminum Porch

Planning Permission

Adding any extension to your house requires expert advice. Part 1, Schedule 2 of The Town and Country Planning (General Permitted Development) (England) Order 2015 allows for a number of types of building works to a house without requiring planning permission.  

Front porches can be built under permitted development subject to a few limitations and conditions. A planning expert can navigate through the planning field and advise whether your proposed front porch needs planning permission.  This check is known as a pre-assessment and is a vital step to preventing unnecessary costs, time and breaches of planning control, which could lead to formal enforcement action.

Front porches can be built under permitted development subject to a few limitations and conditions.

Building Control

For smaller projects, building regulations approval isn’t required where the porch is:

  • Ground level
  • Less than 30 square metres
  • Existing front door remains in situ.
  • It doesn’t adversely affect access.

Compliance with Building Regulations usually relates to when the porch consists of windows and electrical installations. The architect provides the relevant details of the windows, and the electrical works needs to be carried out by a qualified electrician who certifies it is safe and compliant.

 

Costs

The cost of the porch depends on a number of factors, namely the type of porch, size and materials.

 A relative sized porch can cost around £2,500 – £5,000.