Double Storey Extension Cost in 2025: Full Breakdown for Homeowners

A Double Storey Extension is also among the most intelligent options of UK homeowners to expand their homes, add value and future-proof without the inconvenience of relocation. However, with the new standards of construction that have emerged in 2025, the changes in material cost and the new planning expectations of homeowners, people have the same fundamental question in their mind; How much does a Double Storey Extension really cost in 2026?

You need to know how to plan and budget, regardless of whether you want to add more bedrooms, more open plan kitchen, a home office or a combination of functionality and lifestyle areas, you need to understand the financial situation first to plan with confidence. This guide subgelates realistic costs in the marketplace, the key variable in budgets and how specialist architectural teams can guarantee that every pound is optimised throughout the idea to the final destination.

How Much Does a Double Storey Extension Cost?

The cost of a Double storey extension cost in 2026 generally sits between £2,200 and £3,800 per square metre, depending on your location, design ambition and build complexity. In most UK regions outside London, homeowners can expect mid-range costs, whereas London and the South East typically lean toward the upper end. For an average 40m² Double Storey Extension, this places the total build cost between £88,000 and £152,000, excluding the price of professional services, planning fees, structural engineering and finishes.

These amounts increase when house owners choose to use high-quality materials, custom glazing or luxury-level interior options. Meanwhile, the budget can be controlled using the right design choices, effective space planning and prior organisation with contractors and specialists. A Double Storey Extension is a great way to generate high returns on investment, frequently adding 15-25 to the value of a property making it one of the most economically viable home additions on offer.

Key Factors That Change the Price of a Double Storey Build

There is no identical home and, therefore, the price of a Double Storey Extension depends on a number of factors that are somewhat interdependent. One of the best determinants is location, where labour costs, planning requirements and material availability differ across the UK. Your house is no exception and the current design of your house directly influences that; older buildings may need further work on their foundations or reinforcement of their structure, whereas new constructions can be easily integrated into the environment.

A significant role is taken by design complexity. An extension in a simple rectangular form is much cheaper as compared to an irregular or architectural design. Homeowners usually ignore the impact of glazing decisions on budgets. Full-height sliding doors, corner glazing or custom window systems provide a visual effect but raise the cost of supply and installation.

The overall price is also influenced by internal usage. A Double Storey Extension, which will consist of a kitchen or a bathroom will be more expensive because it will involve plumbing, drains, ventilation and high-spec finishes. A basic bedroom or a study, on the other hand, is usually cheaper. Moreover, whether to have a pitched or a flat roof is an essential decision; pitched roofs are more expensive but they last longer and have a better appearance as compared to a flat roof which is styled in a modern manner and is cheap to construct.

Additional variability is presented by external factors such as site access, soil conditions as well as local planning policies. In densely populated cities, the logistics of homes can be more complex than that of rural areas, and the poor soil conditions of the property can increase the costs of foundation. Sustainability decisions that the homeowners make are also relevant in 2025. Materials that are energy efficient, insulation upgrades and environmentally friendly heating systems can be costly to install but less expensive to operate in the long run.

Cost Ranges for Different Sizes and Styles

Most small Double Storey Extensions of approximately 20m2 cost are between £45,000 to £75,000 based on the finishes and the requirements of the structure. It is the perfect size to add a second bedroom on the top and a kitchen or other living room on the ground floor. Between 30m2 and 40m2, medium extensions cost between around £75,000 and £150,000. These provide spacious plans which have the ability to convert the ground floor into an open plan house including the addition of several rooms on the upper storey.

Larger Double Storey Extensions (over 50m2) start at £120,000 and may well exceed £200,000 with architecturally unique designs, bespoke construction materials, built-in smart-home systems and luxurious interiors. On this scale the expansion can be experienced as a logical development of the current house and not an extension.

The architectural style that you adopt affects the budget. The classic Double Storey Extension brickwork that is similar to the house would be affordable since it resembles the common building techniques. A modern addition with steel framing, big-format glazing or minimalist finish is likely to add to the total cost, although can have a tremendous boost to the character and resale of the property.

How Extension Architecture Helps You Plan Within Budget

Having an expert architectural group such as Extension Architecture would help to have your Double Storey Extension planned in a strategic, economical and in accordance with long-term objectives. Planning stage is the stage where the maximum amount of savings may be made and skilled architects contribute to the refinement of layouts, the removal of the expenditures which do not contribute to the final cost, and the maximisation of the natural light and structural efficiency.

Extension Architecture will initiate by a thorough study of feasibility, reviewing the constraints in planning, design opportunities as well as budget expectations. With mapping of realistic cost scenarios being made at the beginning, the homeowners will not be caught off-guard, and they can make appropriate decisions on where to dispose and where to save. The planning professionals in the team manoeuvre through the intricate local policies and provide your project the best opportunity of passing as well as minimising delays that may raise its costs.

The design phase enables materials, construction techniques, and layout choices to be tried out and guaranteed to fit both the aesthetics and the budget criteria of the Double Storey Extension. Technical drawings and building regulations packages of high quality facilitate the tender process as the contractors are able to price correctly and the homeowners are not taken up with the surprise of add-ons.