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Crowded homes, high property prices, and even the recent pandemic has created a need and desire for additional space like never before. This has led directly to a significant increase in the number home extensions built in and on London homes.

One such extension that creates space, privacy, and value is the often-underestimated over garage extension.

Ideal for semi-detached homes, over garage extensions require a solid foundation and strong walls. But when constructed, help add valuable additional living space that is perfect for an extra bedroom or even a quiet home office.

A house extension is the ideal chance for homeowners to increase the living space within their properties without incurring the heavy cost and inconvenience of moving houses.

House extensions are generally categorised based on the area of the property on which they are constructed. As such, house extensions commonly found in London include:

Rear extensions

Built on the rear of a property, rear extensions are immensely popular among homeowners for their versatility and size. They may be used to design kitchen extensions, guest bedrooms, playrooms, or even home offices.

Side return extensions

These extensions utilise the area that runs along the side of a property along with a portion of the rea. They help create beautiful indoor-outdoor connections that are a much sought-after feature of modern dining rooms.

Wrap around extensions

A combination of rear and side extensions to create an L-shaped structure, wrap around extensions add immense width and depth to a property. This allows them to be used for the creation of multiple rooms, larger kitchen-diners, and even open plan living spaces.

Multi-storey extensions

Though more complex than single storey extensions, multi-storey extensions are extremely cost-effective as they essentially double the square footage of an extension without doubling the roofing and excavation costs. They may be used to design additional bedrooms, bathrooms, or even high-ceilinged living and dining areas.

In addition to these extensions, side extensions, modular extensions, loft conversions, and over garage extensions are quickly becoming incredibly popular among property owners in London.

As the name suggests, over garage extensions involve the addition of a room over (or on top of) the existing garage within a property. This basically creates a second storey room to your house.

The rules for over garage extensions differ slightly from conventional extensions. This is because they do not usually fall under permitted developments. However, the House Extension Design Guide for each local authority will have the specific criteria which allows for over garage extensions.

For this reason, to determine the planning approvals necessary for your over garage extension in your specific locality, it is best to check with the local council or even the planning portal.

Some of the specifications and limitations that over garage extensions must abide by to fall under permitted developments include:

  • The extension must not be built on listed properties or those located in conservation areas
  • The extension must not cause a ‘terracing effect’ by extending up to the boundary of the property
  • It must not be higher than the highest part of the house
  • The materials used on the exterior of the extension must be similar in appearance to those on the exterior of the original house

If planning permission is required, a comprehensive application must be submitted. The entire process can take up to 12 weeks for approval.

In addition to planning permission, building regulations approval and party wall agreements must also be considered to ensure that the build complies with building guidelines and standards.

Over garage extensions offer the perfect combination of privacy and connectivity to homeowners. They are therefore ideal for designing:

  • Additional bedrooms
  • Home offices
  • Gyms
  • Utility rooms
  • Studios/ gaming room

The final plan and design of the room created depends largely on the space available, room requirements, the utility connections, and the amenities available.

The costs of garage extensions, especially over garage extensions, are not easy to define, and depend on a number of factors. Chief among these is whether the existing foundations and walls are strong enough to bear the additional load of an extension, or will they need to be reinforced.

Other factors that need to be considered include:

  • The size of the extension
  • The design/ complexity of the extension
  • Building materials
  • Planning permission and building approval fees
  • Utility connections
  • Fittings and fixtures
  • Specialists’ fees, etc.

Therefore, the cost of an over garage extension can range from £20,000 to £80,000.

Good Design and Build offer free consultations and quotations for proposed extensions. This allows homeowners to plan their home extension budgets and designs to their specifications.

Don't move. Extend in style

We can save you the hassle that comes with moving not to mention the heavy stamp duty! Adding an extra loft bedroom or enlarging the living kitchen dining space on ground floor is an economical way of transforming your home to suit growing needs. The projects can range from £40-100K depending on your requirements and can be completed within 8-16 weeks.

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How we deliver projects

Our process is simple and divided into two distinct phases with separate contracts: Design and Build. As a client you only commit to one phase at a time depending on what stage of the process you are in. Each phase consists of three stages as described below.

1. Design

This is the kick-off point for your project. We carry out a complete architectural measured survey of the property. This allows us to create accurate CAD design drawings. This is followed by a design meeting to start discussing your ideas in more detail.

2. Planning

At this stage we finalise the designs with you and start preparing planning applications as needed. We place a high priority on ensuring that plans, designs and schedules are all based on a thorough and detailed understanding of planning guidelines. We co-ordinate with local authorities until the decision is made, and the planning approval is secured.

3. Technical

Once the planning consent is secured, we translate the design drawings into more detailed technical drawings for the purposes of building control and construction. This also includes specifications and structural calculations. At this stage, we will also submit to you our ‘no obligation’ quote for the build phase.

4. Pre-build

90% of our clients decide to stick with us after the design phase is completed. Once the build contract is signed, we kick off the process by making sure all the pre-build processes are complete. These include assistance with party wall agreements, Thames Water build over agreement, submitting building control application, and preparing method statements etc as needed. This stage ends with a pre-start meeting with your foreman before the actual build begins.

5. Build

One of our foremen will be dedicated to your project and will be on-site to manage everyday works. Our project managers will be overseeing the works to make sure they are completed to high standards, within your budget and on time. Throughout the process we will keep you updated with the progress and coordinate the works with third parties such as kitchen or flooring suppliers. We will also advise and guide you to choose any suppliers if needed.

6. Handover

As the build draws to finish, we will help to iron out any ‘snags’ to make sure everything is completed to your satisfaction. We will put together all necessary certificates such as gas, electricity and building control completion along with warranties for glazing, boiler etc. At the final completion meeting, we will hand you these documents, together with the keys to your house. Needless to say, you can contact us any time after this, if you want us to look at something.


This is the kick-off point for your project. We carry out a complete architectural measured survey of the property. This allows us to create accurate CAD design drawings. This is followed by a design meeting to start discussing your ideas in more detail.

At this stage we finalise the designs with you and start preparing planning applications as needed. We place a high priority on ensuring that plans, designs and schedules are all based on a thorough and detailed understanding of planning guidelines. We co-ordinate with local authorities until the decision is made, and the planning approval is secured.

Once the planning consent is secured, we translate the design drawings into more detailed technical drawings for the purposes of building control and construction. This also includes specifications and structural calculations. At this stage, we will also submit to you our ‘no obligation’ quote for the build phase.

90% of our clients decide to stick with us after the design phase is completed. Once the build contract is signed, we kick off the process by making sure all the pre-build processes are complete. These include assistance with party wall agreements, Thames Water build over agreement, submitting building control application, and preparing method statements etc as needed. This stage ends with a pre-start meeting with your foreman before the actual build begins.

One of our foremen will be dedicated to your project and will be on-site to manage everyday works. Our project managers will be overseeing the works to make sure they are completed to high standards, within your budget and on time. Throughout the process we will keep you updated with the progress and coordinate the works with third parties such as kitchen or flooring suppliers. We will also advise and guide you to choose any suppliers if needed.

As the build draws to finish, we will help to iron out any ‘snags’ to make sure everything is completed to your satisfaction. We will put together all necessary certificates such as gas, electricity and building control completion along with warranties for glazing, boiler etc. At the final completion meeting, we will hand you these documents, together with the keys to your house. Needless to say, you can contact us any time after this, if you want us to look at something.

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Build a Quote!

Let's get started with building your own bespoke quote for your dream extension. Tell us as much in detail as possible to get most accurate price.

Get Started

Build a Quote!

Let's get started with building your own bespoke quote for your dream extension. Tell us as much in detail as possible to get most accurate price.

Get Started