Making a double storey extension will help you gain a lot of space and increase your home’s future value. With house prices and problems with available space in the UK, more property owners are choosing double storey extensions rather than moving. You ought to know the full breakdown of costs before you get to the architect and the contractors’ quotes. As well as the initial design, choosing materials and labour will add up quickly and can increase the overall cost. We’ll look at this step by step.
How Much Does a Two Storey Extension Cost in 2025?
In 2025, it is expected that a UK double storey extension cost between £70,000 and £150,000, depending on how much area it covers, its location, how detailed the design is and the finish used. In general, it will cost you between £1,800 and £2,500 per sqm. The work happens on top and bottom floors, but extra costs are involved for bathrooms and kitchens. In the London and South East region, jobs and planning issues often make construction costs more costly. But those in the North or Midlands could see buying prices that are a little lower.
One reason a double storey extension is attractive is that you can get almost twice as much space without paying twice as much. After the foundations and roof are installed, adding another floor above gives much more room at only a small fraction of the cost it would take to build it separately.
Breaking Down the Costs of a 2 Storey Extension
When adding a double storey extension, you’ll need to spend between £2,000 and £5,000 on design and planning for this work, depending if you work with a design-and-build service or choose your own architect and engineer. If you are required to get planning permission, that costs an extra £1,000 to £2,000.
Read more about the double storey extension before and after.
Much of the construction budget covers foundations, all structure work, building walls, windows, roofing materials, plus plumbing and electrical work. When the structure is complete, finishing the interior flooring, applying plaster, painting and adding built-in furniture will enhance the home’s appearance more or less, depending on your preference and budget. A kitchen or bathroom area inside the extension can cost you an extra £10,000 to £30,000.
Include extras like removing waste, skips, insurance and funds just in case things don’t go as planned. It’s always a good idea to set aside at least 10% as a contingency budget.
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Key Factors That Influence Your Double Story Extension Budget
Your total cost for a two-storey extension will depend on a variety of influencing variables. Obviously, the size matters: you can get more affordable work if you pick a modest rear extension, not a large addition. The place where construction happens also matters: costly labour and tough rules for urban development increase the price of building. Design complexity is also a factor. Basic straight-sided additions tend to be cheaper than additions with multiple angles or those made from artistic materials.
When you are knocking down walls, adjusting flooring or need metal support beams, it will add to your expenses. The type of materials you use will also be important. The basic options are brick and blocks, but opting for timber cladding or improved windows and greener insulation will all change the final price. Interior finishes can surprisingly affect the look and feel of a home. Floors and staircases made with special materials can be breathtaking, but they aren’t cheap.
Additionally, you need to make good decisions with your contractor and project manager. Although a trustworthy contractor costs more, they will help you avoid delays, tension and extra expenses. Taking on DIY project management saves money, although it is demanding and takes a lot of time.
Cost Comparison: Ground Floor vs Double Storey Extensions
Sometimes, people aim for a small, one-storey extension because they believe it’s less expensive. It’s correct that projects only on the ground floor tend to be less costly, but they’re not always a better deal. While adding another floor to your home is 50–70% more expensive, you get twice the room. So, adding a one-storey kitchen extension may be between £40,000 and £60,000, but a two-storey extension that also gives you a new kitchen and bedroom could be priced at about £80,000 to £100,000.
Generally, you get a bigger return for your square metre price when you choose a two-storey house. If it’s in your budget and within the rules, building up as well as out is generally a wiser financial move.
Planning Fees, Materials, and Labour: What’s Included
Double check everything that will be included with your double storey extension, once you get a quote. A detailed quote must include the following items:
In this stage, the architect prepares drawn designs, does necessary structural computations and submits a planning permit.
- Getting the site ready involves cleaning the land, preparing the ground, digging foundation holes and laying drains.
- During construction, the elements are built: walls, windows, insulation, roof and internal floors.
- Utilities mean plumbing, electricity and heating systems in a dwelling.
- Interior features: including plastering, painting, laying floors and kitchen or bathroom fitting if listed on the contract.
Notably, upgrades, outdoor landscaping, furniture or driveway work are almost always excluded.
How to Estimate Your Double Storey Extension Cost Accurately
The right option is to hire an architect or a design-and-build team to offer a trustworthy estimate using your plans, the local environment and the materials you choose. The average cost for each square metre is a good start, but it’s a good idea to plan for unforeseen costs if you’re renovating as well.
Before starting construction, it’s wise to finish planning your design. Changes during the project tend to cost more money. If you make any kind of change, loud or small, it can have effects on the rest of the house. Deciding on what you want from the start can help you save a lot of money.
It’s always prudent to get several estimates and make sure they are all itemised by reputable contractors. You can match the expenses and notice the places where more savings might be found. Remember, if you’re doing something like converting a non-residential building into a home, you may be able to claim VAT relief.
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