How Much Does it Cost to Build a Garden Granny Annexe in the UK: A Breakdown of Pricing and What to Expect

More than ever before, people in the UK are planning to ensure that their elderly parents are looked after in their later years, but the cost of care homes is a significant concern. At the same time, grown-up children are struggling to get onto the property ladder and the costs of renting are absorbent, with no investment to show in the end.

Homelodge offers a unique solution. Established in 1986, Homelodge has designed a range of bespoke high-quality garden annexes, commonly known as granny annexes, which provides a detached, highly insulated self-contained living space in the garden. It’s the perfect solution, offering independence, security and freedom and it’s designed to be exempt from planning permission but still can conform to building regulations.

All Homelodge annexes are built strictly to meet the Mobile Home Act and exceed the insulation requirements covered by BS3632:2023, keeping utility bills to a minimum and thus offering a perfect all-year-round comfortable home in the garden.

By complying with the Mobile Home Act, VAT is zero-rated (with the exception of the kitchen appliances, carpets and landscaping). This means that unlike any other forms of extending your house, which require the additional 20% VAT (unless your tradesperson is under the VAT threshold of £90,000.00 turnover a year).

So, How Much Does it Cost to Build a Granny Annexe?

Each Homelodge annexe is bespoke, tailored to your needs, garden, and budget. We offer a free site survey, where our experienced surveyor will assess your space and discuss your requirements. After this meeting, we can provide a 3D plan and a fixed price for the entire project. Because we manage the process from start to finish, there are no unexpected costs or surprises. So you will know how much it will cost to build your granny annexe prior to placing your order.

On our website we have sample plans of previous annexes, together with the price guides. On our website, you can view sample plans and pricing guides. Our interactive tool allows you to filter by the size of the annexe, number of bedrooms, and price range, helping you see what’s achievable within your budget.

Our Range of Annexe Designs

Premier Range

The Homelodge Premier range features a standard width of 6m (20 feet) with length options up to 6m x 18m. This setup can accommodate up to four bedrooms, plus additional bathrooms and utility rooms—potentially turning your annexe into a dream home.

Click the link for sample Premier plans and see what the Premier granny annexe cost: https://www.homelodge.co.uk/annexe_type/premier/

Heritage L-Shape

Ideal for smaller or tighter spaces, this L-shaped design nestles into the corner of your garden, creating a secluded internal courtyard. With vaulted ceilings and a hip roof, it includes a fully fitted kitchen, bathroom, bedroom, and living area—all tailored to your needs.

Click the link for sample L-Shape plans and see what the Heritage L-Shape granny annexe costs: https://www.homelodge.co.uk/annexe_type/l-shape/

Heritage

Designed for a width of 3.6m (12 feet), the Heritage range features flexible internal layouts and finishes. With a distinctive vaulted ceiling, visible trusses, and a hip roof, these annexes include a fully fitted kitchen, bathroom, bedroom, and living space.

Click the link for sample L-Shape plans and see what the Heritage granny annexe costs: https://www.homelodge.co.uk/annexe_type/heritage/

What Influences the Cost?

Your final granny annexe cost depends on your site conditions and the specifications you choose. Our free site survey ensures expert advice on the most appropriate design, materials, and features to balance functionality, durability, and aesthetic appeal.

Partnering with a company that conducts a full on-site survey and provides a fixed price is vital to avoid uncertainties. Our surveyor will review:

Access – Don’t worry if you haven’t got a side alleyway there are various solutions available to us to ensure we can install your annexe in the ideal location. If you have any concerns just call and if you don’t want a site survey, we can often review access via a desktop survey.
Location of site – we have various options if your garden slopes, and we can guide you through the implications of each option during our site survey. The two main options for overcoming a slope are;
- Cut into the bank and install a retaining wall – this will drop the height of your annexe and allow it to nestle into your garden.
- The more cost-effective solution is to build the foundation padstones up and elevate your lodge. This can then be finished off with a raised decking, which can create beautiful, elevated views.
Ground and site conditions – our traditional system is foundation padstone, which is appropriate for most sites, however, we do have options if this is not suitable, for example;
- Site with clay soils and trees close by – we can use a screw pile system top off with a steel chassis. You do not need a piling rig for these screw piles, and they are ideal for sites with limited access and can be used near trees and in root protection zones of trees with Tree Preservation Orders (TPOs).
- Flood risk zones – we can elevate the annexe above flood risk zones, allowing access via steps or a ramp to the raised decking.
- Building over public main drains and mains water – as our annexes are designed to be relocatable, and we can engineer our foundations to avoid damaging existing services, we have established that we can build over these public services. If your annexe needs to be positioned over a main drain or mains water, we can handle all negotiations with your utility provider to obtain the necessary build-over agreement. If your site is close to a gas main, please contact us—our team can guide you through the relevant legislation.
- Building under a mains powerline – Constructing a granny annexe beneath or near mains power lines is possible, and there are established safety codes of practice to follow. We will ensure your project aligns with these standards and can manage all negotiations with the utility company to facilitate a safe and compliant build.
Site services – these are generally taken from the main house, and our surveyor will review the existing services, and we will undertake a utilities asset search. Over our 39 years of trading, we have the experience in-house to overcome any and all challenges that arise, so please don’t worry. Some common concerns are;
- Foul drains – if you can’t achieve gravity fall back to the main house inspection chamber, don’t worry, we have the solution. The first option is to install an external heavy-duty pumping chamber. Please don’t confuse this with a macerator behind your toilet, which we would not recommend. The heavy-duty pumping chamber is buried in the ground outside the footprint of your annexe. The foul water has a gravity fall from the Homelodge to the pump, and from here the waste will be pumped away. Another alternative is to install a sewage treatment plant; this is not cheap but is an option if the house system has no access to mains drainage and the existing system has reached its capacity.
- Storm water – We would normally install a soakaway which takes the surface water of the Homelodge but other options are available based on ground conditions.
- Electrics – We would require a 60amps supply at the lodge end. We will review your existing supply and advise you if you need your meter head increased. These are usually done free of charge. In the unlikely event that your Homelodge needs a new dedicated supply, we can assist with the negotiations with your utility company
- Water – if you are concerned about water pressure we can undertake a pressure test and there are a range of alternatives to improving water pressure which we can guide you through after our survey.
- Data, TV and telephone – we lay a duct within the common trench to the main house so we can draw through all the cables you need and leave a drawstring for future proofing.
Landscaping – We are delighted to offer a full turnkey solution so we will be happy to design and install the landscaping to and around your Homelodge. This can be fully costed upfront, so you will know the true granny annexe costs from the outset.

Is a Garden Granny Annexe an investment?

A Homelodge is a prudent investment, whether you are saving costs on residential care homes for your parents, or for young family members saving on absorbent costs of rents and the annexe remains an asset to the estate.

It is ideal for multigenerational living where all parties can live close by but maintain their independence, security and freedom.

Book a site survey today and begin designing your tailor-made annexe. We’ll provide a full turnkey quote with a fixed price, giving you peace of mind and clarity on the true granny annexe costs.