Granny Annexes
Self-Contained Living Spaces Designed Around You
A Granny Annexe is a secondary building – a self-contained space designed within the grounds of an existing dwelling, which will either be attached to the main dwelling or separate. Despite the name, a Granny Annexe can be used for a variety of purposes, including a room for guests, teenagers or even as an Air BnB or rental space.
The beauty of a Granny Annexe is that you can create space for your growing family without needing to move, and whilst adding value to your property. If your Granny Annexe is for an elderly relative, there is still a sense of independence if needed from those in the main property, whilst being within a safe distance. As such, Granny Annexes are often seen as cost-effective alternatives to a care home or retirement home.
Our Granny Annexes
Modern Modular Extensions Designed Around Your Home
All of our Granny Annexes are fully insulated and linked to mains electricity. If you add a kitchen this will deliver fully independent living in close proximity to the family. As such, they can be considered for living all year-round. Since they are usually constructed in a garden, they can also benefit from outdoor space too, like a decked area.
Explore More Ways to Extend Your Home:
Conservatory Conversions
Granny Annexes
Garden Rooms
Why Modular?
A SMARTER WAY TO CREATE INDEPENDENT LIVING SPACE
Modular builds differ from traditional builds in that the construction of the wall and ceilings take place in a factory off-site. The components are then delivered when they are needed to the site and can be fully constructed in hours.
Modular Granny Annexes are engineering in precision manufacturing environments, so they are amazingly airtight. Each component fits perfectly, ensuring up to 70% less air leakage than traditional builds. This means a warm, insulated environment which requires less heating than a traditional build.
A stand alone Granny Annexe will have an epc rating of A and comply with the current building regulations.
Fast Installation
Because the structure is built off-site, installation on your property can be completed in a matter of hours.
Precision Build Quality
Because the structure is built off-site, installation on your property can be completed in a matter of hours.
High Airtightness
Because the structure is built off-site, installation on your property can be completed in a matter of hours.
Energy Efficient
Because the structure is built off-site, installation on your property can be completed in a matter of hours.
Modular Granny Annexes deliver faster installation, superior airtightness and energy-efficient living — all designed for comfort, independence and long-term performance.
WHAT YOU NEED TO KNOW
Using Your Granny Annexe for Rental or Independent Living
Can I use my Granny Annexe for Air BnB?
It is becoming increasingly popular to have additional, fully contained living spaces built with a view to them being monetised through platforms like Air BnB. This means a reality where the entire cost of the Annexe can be paid for in as little as two years!
All of our modular rooms are built to live-in standard and could be used for air BNBs with the correct planning application.
Do I need planning permission for a Granny Annexe?
Whether you will need to apply for planning permission for your Annexe depends on a number of factors. The main rule is that if the Annexe is considered part of the mail dwelling, Modexa Build will consult on your behalf once we have agreed the specification of the Annexe. Take a look at our guide for planning permission here to find out more, or simple drop us a line to chat through your ideas.
Regarding council tax: If the Granny Annexe is being used by a dependant family member, then it will be exempt from additional council tax.
CONFIGURATIONS & SIZES
What can your Granny Annexe include?
Granny Annexes will normally be configured into at least three separated spaces: living space including kitchen, bedroom and bathroom. However, more bedrooms can be added, and a kitchen can be separated from the living space creating even more rooms. Modexa Build will construct your new space completely bespoke, to suit your exact needs.
In terms of heating options, we often get asked to equip our modular rooms with underfloor heating, as this is a luxury that is valued by the young and old alike.
In terms of size, since a Granny Annexe is effectively a self-contained dwelling, it will typically be a larger space. We would usually consider a starting size of at least 20m2.
Living Space with Kitchen
Additional Bedrooms
Bathroom
Bunk Bedrooms
Underfloor Heating
Self-Contained Living
Need help designing your annexe? Contact our team to create a layout and size tailored perfectly to your home, space, and lifestyle.
Why choose Us?
Why Modexa Build?
First and foremost, we are experienced construction experts, capable of handling the entirety of your project.
With decades of experience and numerous completed projects, you can trust us to take your vision and turn it into reality.
You will find us full of ideas for what your annexe could be like, so feel free to come to us with a basic concept — and we’ll take it from there.
End to End Project Management
From first idea through to completion
Decades of Experience
Trusted knowledge built over many projects
Creative Design Input
Helping shape your annexe from the start
Detail-Focused Approach
Care and precision in every build
Friendly, Professional Team
Easy to work with throughout the process
You will find us full of ideas and ready to help bring your annexe to life. Contact us now to start the conversation.
Finishes
Built to Look Exceptional and Perform Better
We offer a full range of interior and exterior finishes, depending on whether you want your extension to blend in with your existing property, or stand out and make a statement! We have experience of a number of aesthetic embellishments depending on your taste.
Here are just some of our options:
Brick Slips
Render
Aluminium Cladding
Zinc Cladding
Timber Cladding
Finally, by combining two or more different materials, we can give your modular extension a unique, bespoke and breathtaking finish!
Take a look at our Guide to Modular Extensions for more information about finishes.
High-Performance
improve your home’s carbon footprint
Our modular extensions are designed to deliver exceptional energy efficiency, improved comfort, and long-term value for your home.
EPC Performance
Modexa’s modular extensions are built using our modular system and are designed to achieve very high EPC ratings, typically A or high B, thanks to precision factory manufacturing, high insulation levels and reduced thermal bridging.
This will be a stand-alone rating and will be added to the main house rating, often meaning your extension will outperform your main house.
Higher EPC ratings mean:
- Lower energy bills.
- Reduced carbon emissions
- Increased property value/ resale value
- Better mortgage and lending options
Air Tightness & Thermal
Because Modexa modular extensions are manufactured in controlled factory conditions, construction tolerances are far tighter than traditional building.
This results in:
- Significantly reduced air leakage
- Improved thermal efficiency
- Consistent insulation installation
- Lower heating demand
Typical modular airtightness levels can be 70% better than many traditional builds.
Renewable Energy Ready
Modexa Modular extensions are designed to integrate seamlessly with modern renewable technologies such as:
- Solar PV systems
- Air source heat pumps
- Smart energy systems
This ensures your extension is ready for the future – High Performance Living.
Build smarter. Live better. Talk to our team now to deliver exceptional energy efficiency.
Pricing
what’s included in the price
Our pricing is based on the size of your annexe, giving you a clear idea of costs from the outset. Use the guide below to estimate your project and what’s included as standard.
All prices are estimates and may vary depending on site conditions.
Depth (from existing house) (m) | Length (m) | |||||||
3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | |
3 | £37,966 | £42,703 | £47,440 | £52,177 | £56,914 | £61,651 | £66,388 | £71,125 |
3.5 | £40,518 | £45,925 | £51,332 | £56,739 | £62,145 | £67,552 | £72,959 | £78,365 |
4 | £43,070 | £49,147 | £55,223 | £61,300 | £67,376 | £73,453 | £79,529 | £85,606 |
4.5 | £45,622 | £52,369 | £59,115 | £65,861 | £72,607 | £79,353 | £86,100 | £92,846 |
5 | £48,174 | £55,590 | £63,006 | £70,422 | £77,838 | £85,254 | £92,670 | £100,086 |
5.5 | £50,726 | £58,812 | £66,898 | £74,984 | £83,069 | £91,155 | £99,241 | £107,326 |
6 | £53,278 | £62,034 | £70,789 | £79,545 | £88,300 | £97,056 | £105,811 | £114,567 |
What's Included
- Foundations*
- Floor slab or sub-floor construction
Eco Rend Accredited render
- Underfloor heating installation to the extension area only
- External walls and primary structure
- Flat roof system
- Supply and installation of one window, one roof lantern and 3-leaf bi-fold door set
- Basic drainage connection and tie-in
- Boarded and skimmed
This package provides a secure, weatherproof structure ready for internal fit-out works.
* Standard foundations assumed until survey on site:
Single Story extension foundations standard = 600mm wide 300mm thick concrete foundation, 1000mm to bottom of foundation.
Double Story extension foundations standard = 750mm wide 300mm thick concrete foundation, 1000mm to bottom of foundation.
What's not Included
- Internal structural alterations and calculations
- Internal walls
- Additional External items (patio, paths etc)
- Electric, plumbing & heating (apart from underfloor heating in the extension)
- Decoration
- Flooring & skirting
- Lighting & sockets
- Kitchen supply & installation
A full package can be undertaken by Modexa build; Pease contact us for further information or a quick estimate.
Benefits
Modular vs Traditional Extensions
See how modular construction compares to traditional building methods across key areas that matter most.
Speed of Construction
Modular
A modular build can be completed up to 70% faster than a traditional build, and with a total lead time of 4-6 weeks
Traditional
Traditional builds are subject to on-site delays. For example, glazing cannot be ordered until the brick is completed
Cost
Modular
You will get a fixed price from Modexa Build, with no hidden charges to worry about
Traditional
Variable costs where the original budget can often be exceeded
Your build time
Modular
All components will arrive exactly on time, when they are meant to, reducing disruption and uncertainty
Traditional
Much more difficult to estimate, leading to delays and protracted build times
Quality
Modular
Built in a controlled manufacturing environment for a consistency of quality
Traditional
Subject to a number of variations, such as labour, material, climate etc
Design
Modular
Manufactured bespoke for every project to meet your exacting needs
Traditional
Custom builds can be slow and lead to additional cost
Energy Performance
Modular
High performance due to minimal air leakage and type of materials used
Traditional
Will exhibit most of the energy loss associated with traditional build
Process Management
Modular
Processes follow similar standards so are streamlined and executed with vast experience
Traditional
Every build is different, each crew can differ, the list of sub contractors can also differ
Site Impact
Modular
Minimal disruption for a shorter amount of time
Traditional
Significant disruption over a protracted period of time
How it Works
How our design and build process works:
1
Consultation
Get in touch with us for an initial, no obligation chat about your potential project. You’ll find us experienced, professional and full of ideas. What do you want from your extension? How is it going to improve your living space?
2
Site Assessment
In order to provide you with an accurate quotation, and discuss your vision in situ, we will visit the site of the proposed build and consult with you about what can be achieved.
3
Design and Quotation
We will provide you with a tailored proposal resulting from our consultation. The proposal will be fully costed and give you accurate information around delivery and lead times, including specifications and technical drawings.
4
Off-site Construction
Whilst the superstructure is being manufactured off-site with our manufacturing partners, we will be preparing your site for delivery, so that, on delivery, everything goes as smooth as possible.
5
Delivery and Installation
With a fully-prepared site now in place, all modules will arrive ready to assemble, with installation fully completed within days.
frequently asked questions
Your Questions, Answered
Here are some of the most common questions about our modular extensions, pricing, and process.
Think of a Granny Annex as being a fully contained extension in which someone can live, with everything they need. A granny annex will be a larger extension, fully equipped with a kitchen, bathroom, bedroom and living space.
Because a Grany Annex is effectively a self-contained unit, they tend to be larger in size. It would be safe to assume that a granny annex would be between 40 and 70 metres squared.
A Granny Annex is a larger extension, so will be one of the more expensive extension options. TAKE A LOOK AT OUR GUIDE TO MODULAR EXTENSION COSTS HERE
It is very likely that a Granny Annex would increase the value of your house, although it may limit the market in terms of whether the buyer needs the annex or not. However, since Granny Annexes can also be perfect for larger families or guests, they should be viewed as highly purposable.
Yes. Every Granny Annex will have all the main utilities shared by the primary house – heating, water, Wi-Fi etc.
Modular builds are perfect for a Granny Annex, being so flexible, and manufactured bespoke for each project.
Still have questions? Contact our team for friendly advice and guidance.
Questionnaire
Ready to Transform Your Home?
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