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by Sean Hill on Dec 6, 2024
Semi-detached houses are more than just a staple of the UK housing landscape - they’re a symbol of potential. With almost one-third of the nation’s homes falling into this category, these properties hold untapped opportunities for transformation. A shared wall on one side and an open boundary on the other offers a canvas for creating spaces that enhance living, spark joy, and meet modern needs.
At RISE Design Studio, we see extensions not just as additional square meters but as a way to rewrite how you live in and experience your home. Let’s explore the possibilities of semi-detached house extensions and uncover the considerations that lead to purposeful, inspired results.
Douglas House in Kensal Rise, NW London, includes a rear extension as well as hip to gable roof extension
How Far Should You Extend? Start with the Right Questions
The first question isn’t, “How much can I extend?” but rather, “How much do I need to extend to live better?”
Yes, Permitted Development (PD) rights may allow you to extend up to 3m - or even 6m if your property qualifies - but building the biggest extension isn’t always the best solution. Sometimes, it’s about achieving more with less: maximising light, flow, and functionality without overwhelming your space or budget.
Your home’s context - its location, planning history, and proximity to neighbours - will shape what’s possible. But context should also inspire creativity. Every home has a story, and every extension is an opportunity to write the next chapter.
Two-Storey Extensions: A Bold Statement of Vision
Two-storey extensions may seem ambitious, but they are often where the magic happens. They allow for a bolder reimagining of your home’s layout, creating vertical connections and new perspectives.
Planners will scrutinize the impact of height and mass on your neighbours - particularly using the 45-Degree Rule - but this is where thoughtful design shines. By balancing boldness with sensitivity, you can achieve an extension that feels natural yet transformative.
And here’s the entrepreneurial wisdom: economy of scale matters. While the upfront cost may seem higher, the cost per square meter for two storeys is often lower than for a single storey. You get more value, more function, and more home.
Douglas House twilight photo
Permitted Development (PD): Freedom Within Boundaries
Permitted Development rights offer a framework for extending your home without the hurdles of full planning permission, but they come with rules that shape your design choices:
- Extensions cannot cover more than half the land surrounding the original house.
- Side extensions are limited to a maximum height of 4m and a width of half the original house.
- Rear extensions can reach 3m - or 6m with prior approval - if they meet specific criteria.
These rules may feel restrictive, but within them lies an invitation to innovate. Great design isn’t about what you can’t do; it’s about what you can create. If PD applies to your property, securing a Certificate of Lawfulness provides peace of mind and ensures your vision aligns with regulations.
What Does It Cost to Extend a Semi-Detached Home?
Investing in your home is an investment in your future. Based on our experience:
- A single-storey extension in Greater London typically costs £3,600–£4,900 per square meter.
- A two-storey extension offers better value, thanks to shared foundations and economies of scale.
But costs go beyond square meters. The materials, finishes, site conditions, and even the unseen challenges below ground all shape the budget. At RISE, we believe transparency in budgeting builds trust - and trust is the foundation of great collaborations.
Transforming the Ordinary into the Extraordinary
At RISE Design Studio, we believe in the power of purposeful architecture. Extending your semi-detached home isn’t just about adding space; it’s about transforming the way you live and creating something meaningful.
Every project starts with a conversation. A shared vision. A belief that your home can do more than shelter you - it can inspire you.
If you’re ready to take the next step in your home’s journey, let’s design something extraordinary together. Get in touch with team at RISE Design Studio today!
