Double Storey Extensions
Add More Space. Build More Value. All with One Trusted Team.
Expanding your home shouldn’t be complicated. Our double storey extension service gives you the extra space you need, upstairs and down, while enhancing the design, flow and value of your property. From concept to completion, we manage the entire process: planning, design, permissions and build.
We deliver high-quality, buildable architecture that fits your lifestyle, complies with planning rules and stays on budget with a 6-year structural warranty for total peace of mind.
Why a Two Storey Extension Makes Sense
Smarter Use of Space
A double storey extension makes better use of your plot and budget than a single level build. It is ideal for families wanting extra living areas, bedrooms, bathrooms or workspaces, while keeping the overall footprint compact and practical.
Flexible Design Options
Whether it is a double storey rear extension, side addition or wraparound, we create designs that blend with your existing home and meet planning rules. A double storey extension adds room below for living space and upstairs for bedrooms or offices.
Value and Cost Efficiency
A double storey extension reduces cost per square metre compared to single storey projects, improves flow and function, and boosts your property’s resale value, making it a smart long-term investment for any homeowner.
Designing a Double Storey Extension That Works
Design That Delivers More Than Looks
Good design goes beyond aesthetics, it ensures your extension is functional, buildable, and approved without delay.
Practical Planning with Expert Support
Our in-house architectural designers and planning consultants take a practical approach that considers your budget, the existing property layout, and local planning authority requirements.
Specialists in Two-Storey Extensions
We specialise in designing two-storey extensions for all types of homes, from terraced houses to detached family homes, always with structural integrity and build cost in mind.
Comprehensive Design and Cost Transparency
Every design includes a comprehensive feasibility review and multiple layout options, planning-compliant drawings and elevations, and clear cost alignment from the start.
Guidance Through Regulations and Planning Challenges
We also provide expert guidance navigating conservation areas and ridge height limits, alongside face-to-face architect meetings to keep your project moving smoothly.
95%
of our clients say
they’d build with us again
"Happy Building guided us from planning to build with zero stress — and stayed exactly on budget. We’d do it again in a heartbeat."
150+
"Nothing but positive words to say about our experience with Happy Building so far. Geo took our brief and nailed it more or less straight away and we've been impressed with the service to date. Working with Geo on our project has made life a whole lot easier & something that initially seemed so daunting/stressful has so far been a delightfully calm experience. Can't wait to see what comes next."
6 in 10
“We chose Happy Building because they provide both the design and build process, and we had seen their local projects and were impressed. Happy Building has a straightforward process — we knew exactly what was happening and when. We knew what the cost would be and there were no surprises. They were proactive in their approach to any challenges that came up — they always came with a solution. Their team were accessible, engaged, and helpful at all stages. The build has transformed our house and changed the way we live in it — it’s better than we thought it would be!”
“We were very pleased with our experience working with Happy Building, especially Geo. He designed us a range of fantastic designs, including costing them up transparently and fairly. He was patient with our differing decisions, gave really sound advice, and communicated with us promptly and clearly. We wouldn't hesitate to recommend them!”
95%
of our clients say
they’d build with us again
"Happy Building guided us from planning to build with zero stress — and stayed exactly on budget. We’d do it again in a heartbeat."
Do You Need Planning Permission?
We’ll Let You Know.
Not all double-storey extensions need full planning permission, some fall within permitted development rights, depending on their size, location, and design.
However, most will require a formal application, particularly if you’re building near a boundary or altering the roofline. We help you determine if planning permission is necessary, what limitations may apply, and how local regulations, especially in conservation areas, affect your plans.
With a 99% planning approval success rate, we handle the entire process, from drawings to submission, so you don’t have to.
Double Storey Extension Costs & Planning Explained
Understanding the true cost of your double-storey extension begins with a clear, tailored plan. We provide detailed, itemised estimates based on your property, goals, and location, ensuring transparency from the outset. Whether you’re in the early design phase or ready to build, we guide you through every financial and regulatory aspect. Our service includes accurate cost-to-build estimates using current 2025 rates, comparisons between single and double-storey options, full planning application support, and expert advice on development constraints. We also coordinate architecture, engineering, and project management for a seamless experience. Need clarity on your budget? Try our extension cost calculator or book a free consultation for personalised figures and timelines.
Building a Double Storey Extension Done Right
We’re more than just designers, we also build what we draw. With a fully insured, highly rated construction team, we manage your extension from groundworks to final finishes, ensuring no handovers or gaps. Our process includes a dedicated senior project manager, regular progress updates, and seamless communication to keep everything on track. You can expect a 6-year structural warranty, compliance with all building regulations, skilled tradespeople, and high-quality materials. Whether it’s a double-storey side extension or a full rear upgrade, our craftsmanship and client-first approach ensure a smooth, stress-free build.
Start Your Extension Journey Today
Considering a two-storey extension? We make the entire process simple. Planning, approvals, and construction, all handled by one expert team.
