When space runs out at home, most people’s first thought is to move. But with house prices still high, estate agent fees, stamp duty, and the general upheaval of relocating, it often makes more sense to stay put and make better use of the home you already have. For many families, that means extending and in particular, building upwards. At Rosebrick Developments, one of the most common questions we get is simple: is a double storey extension really worth it?

We think the best way to answer that is to explain what it is, how it works, and what you’re actually getting for your money based on the real-world experience we’ve had on building sites up and down the UK.

What is a Double Storey Extension?

A double storey extension is a two-level addition to your home, normally extending the rear or side of the property. On the ground floor, it typically adds a large kitchen-diner, utility room, office, or family space. Upstairs, it can create extra bedrooms, a new bathroom, or free up space to remodel your existing layout. You don’t just gain square footage—you can completely reshape how your home functions. In many cases, the end result feels like a brand new house, but without the cost or hassle of actually buying one.

The Main Appeal: More Space, Less Cost per m²

One of the biggest misconceptions is that double storey extensions cost twice as much as single storey ones. They don’t.

You’re only paying once for the most expensive parts of the build, foundations, roof, scaffolding, site set-up. Once those are in place, building upwards adds space at a much lower cost per square metre.

That’s why double storey extensions often offer far better value for money in terms of what you get.

Costs to Expect

Let’s be honest—this isn’t cheap. But it can be one of the most efficient uses of money if done properly. Based on our experience at Rosebrick Developments, here’s a rough guide:

  • Build cost per m²: £2000–£3,500 depending on spec, complexity, and access

  • Total cost: Most clients spend between £100,000–£160,000 for a standard 2-storey side or rear extension

  • Extras: You’ll also need to budget for planning (if required), architectural drawings, structural calculations, finishes, and VAT

We always give a full breakdown and fixed-price quote before starting. Why not try our instant estimator and get a rough idea of cost!

Does It Add Value to the Property?

Yes—and often more than you spend.

Adding a double storey extension can increase your property value by 15–25%, depending on your area, layout improvements, and local demand. If your house gains a bedroom and an improved kitchen or bathroom, that’s money back in the bank when you eventually sell.

In areas where loft conversions or side returns aren’t viable, this becomes one of the best routes to growing your space and your home’s value.

What Are the Planning Rules?

Planning permission is often needed for double storey extensions, especially if you’re building close to boundaries, going above existing height, or altering the roof. Even if the extension might fall under Permitted Development, it’s still wise to get a Lawful Development Certificate to avoid issues later.

If you’re in a conservation area, on a corner plot, or your design affects the street view or neighbours’ light and privacy, expect closer scrutiny. Councils look for designs that match the character of the area and won’t cause disruption.

At Rosebrick Developments, we manage the whole planning process—working with architects, preparing the right drawings, and dealing with local authorities so you don’t have to. We make sure your project gets approved without unnecessary delays.

What Can Go Wrong?

Let’s not sugar-coat it. If badly planned or rushed, a double storey extension can cause major headaches.

Here’s what we’ve seen others get wrong:

Poor Design

One of the biggest mistakes is adding space without thinking through how it actually works. We’ve seen extensions that add square metres but ruin the flow of the home—awkward room shapes, dark corridors, or a layout that makes no sense. A well-designed double storey extension should feel like it was always part of the house, not bolted on as an afterthought.

No Contingency Budget

Unexpected costs are common in construction. Ground conditions, drainage issues, structural surprises; any of these can hit mid-build. If there’s no buffer in your budget, you risk stalling the whole project or having to cut corners. We always advise clients to allow for at least 10–15% contingency on top of the main build cost.

Bad Site Access

It’s easy to overlook how materials and machinery will actually reach the site. With rear extensions in terraced properties, for example, poor access can slow everything down, raise costs, and limit what equipment can be used. We assess this from day one so there are no surprises once the build starts.

Cheap Labour

Trying to save money by going with the cheapest quote is a false economy. We’ve seen horror stories; unfinished work, structural problems, rogue traders walking off mid-job. At Rosebrick Developments, we only use experienced trades we trust and manage the entire process ourselves. It’s the only way to ensure quality and avoid nasty surprises.

How Long Does It Take?

From first drawing to moving into your new space, allow 5–7 months:

  1. Design & planning: 6–10 weeks

  2. Structural engineering and prep: 2–4 weeks

  3. Build: 12–16 weeks depending on weather, complexity, and finish

We provide a detailed schedule before works begin and keep you updated each step of the way. We also minimise disruption as much as possible—especially if you’re living in during the works.

Is It Worth It?

Here’s the straight answer: if you want to stay in the same area, love your current house, and need more space, a double storey extension is one of the smartest things you can do.

It’s not a shortcut. It’s a long-term investment that, when done right, pays off in quality of life, property value, and usable space. You’ll get the home you actually want, without having to move to get it.

Why Choose Rosebrick Developments?

Are you based in the Derbyshire, South Yorkshire, Mansfield or the local Nottinghamshire area? Get in touch! We’re not a volume builder. We focus on quality residential extensions for clients who care about getting it done properly. With us, you get:

  • Clear communication and honest pricing

  • Full design and build support

  • A tidy site and a professional crew

  • A finished space you’ll actually love

Thinking about a double storey extension? We’ll talk you through the numbers, the options, and what to expect.

Get in touch with Rosebrick Developments today.