If you’re looking to add extra space to your property, you’ve probably come across three popular options: granny annexes, modular homes and bespoke garden rooms. Each offers a practical solution for creating additional living or working space, but which one gives you the best value for money?
In this guide, we’ll break down the costs, benefits and considerations for each option to help you decide which is the most cost-effective choice for your needs.
What Is a Granny Annexe?
A granny annexe is a self-contained living space, typically built in the garden of an existing property. These annexes usually include a bedroom, bathroom, kitchen and living area, making them ideal for elderly relatives who want to live independently while staying close to family.
Granny annexes can be constructed using traditional building methods or prefabricated modular techniques. Because they’re designed as fully functional homes, they often require planning permission and must meet building regulations.
Typical costs: £40,000 to £100,000+ depending on size, specification and whether utilities need to be connected.
What Is a Modular Home?
Modular homes are prefabricated buildings constructed off-site in a factory, then transported and assembled on your land. They range from compact single-storey units to large family homes with multiple bedrooms.
Because modular homes are built in controlled factory conditions, construction times are faster and there’s less waste compared to traditional builds. However, they typically require their own plot of land with appropriate planning permission, which adds to the overall cost.
Typical costs: £80,000 to £250,000+ depending on size, design and land preparation requirements.
What Is a Bespoke Garden Room?
Bespoke garden rooms are standalone structures built in your garden, designed to suit your specific requirements. Unlike granny annexes, they’re not intended as permanent living accommodation. Instead, they’re used as home offices, gyms, studios, playrooms or entertainment spaces.
Garden rooms are generally quicker to install and more affordable than annexes or modular homes. Many designs fall under permitted development rights, meaning you may not need planning permission—though it’s always worth checking with your local authority.
Typical costs: £15,000 to £50,000 depending on size, specification and interior fit-out.
Comparing the Costs
Here’s a quick overview of how the three options compare:
| Option | Typical Cost | Planning Permission | Build Time |
|---|---|---|---|
| Granny Annexe | £40,000–£100,000+ | Usually required | 8–16 weeks |
| Modular Home | £80,000–£250,000+ | Required | 12–20 weeks |
| Bespoke Garden Room | £15,000–£50,000 | Often not required | 2–6 weeks |
As you can see, bespoke garden rooms offer the most affordable entry point and the fastest installation time. They’re also the simplest option from a planning perspective.
Which Option Offers the Best Value?
The most cost-effective choice depends on what you need the space for.
Choose a granny annexe if you need fully self-contained accommodation for a family member. While the upfront cost is higher, it could save thousands compared to residential care fees or renting a separate property.
Choose a modular home if you’re looking to build a standalone property on a separate plot of land. This is a significant investment, but modular construction can be more affordable than traditional building methods.
Choose a bespoke garden room if you need flexible extra space without the complexity of a full building project. Whether you want a home office, gym or studio, a garden room delivers excellent value with minimal disruption.
For most homeowners, a bespoke garden room strikes the best balance between cost, convenience and versatility. You get a high-quality, purpose-built space without the expense and red tape associated with larger construction projects.
Why Choose Smartbuild?
At Smartbuild, we specialise in designing and building bespoke garden rooms tailored to your exact requirements. From compact home offices to spacious multi-use buildings, we create beautiful, functional spaces that enhance your property and your lifestyle.
Our team handles everything from initial design through to installation, ensuring a smooth, stress-free experience. Every garden room we build is constructed to the highest standards using premium materials, giving you a space you’ll enjoy for years to come.
Ready to Get Started?
If you’re considering a granny annexe, modular home or bespoke garden room, we’d love to help you explore your options. Our friendly team can advise on the best solution for your property, budget and requirements.
Contact Smartbuild today to arrange a free, no-obligation consultation. Call us or fill out our online enquiry form to get started.