Single Story Extension Cost In UK

Single Story Extension Cost In UK Opinder Singh Dhillon Kulveer Singh Sanghera

Single Story Extension Cost In UK

Adding a single storey extension to your home can provide valuable extra space and significantly enhance your living environment thought it’s crucial to understand the costs involved before embarking on such a development. Looks highlight the factors influencing single-story extension costs in the UK together with tips to help you plan your budget.

Size and Design Complexity

Project size and design complexity play the biggest roles in determining the single story extension cost. Larger extensions naturally require more materials, labour, and potentially additional structural work, leading to higher expenses. Similarly, complex designs involving unique architectural features or challenging structural requirements may also increase costs.

For example a simple block and brick Lane to extension on a Victorian mid- terraced home, could cost as little as £30,000, all range up to several times that depending on the amount of opening up required and backward integration through the rest of house. So consider balancing your desired extension size and design complexity with your available resources when deciding if the project is feasible.

Site Conditions & Location

Your single story extension cost will also be influenced by location and site conditions. Factors such as access to your property, proximity to utilities, and the need for groundwork can impact overall expenses. Where the terrafirma is marshy for example, pile foundations may be required which are several times more expensive than the standard poured concrete trench foundation which may be suitable on firm ground. 

Sites with difficult access or challenging terrain may require additional work, such as excavation or reinforcement, which can raise costs. Research local building regulations and consult professionals to determine any site-specific challenges that may affect your project’s budget.


The choice of materials for the build will significantly influence the single story extension cost. Different materials vary in price, durability, and aesthetic appeal. For example, opting for premium materials like hardwood flooring or bespoke fixtures will increase costs compared to more affordable alternatives. 

Balancing your desired aesthetic and budget is crucial when selecting materials. Research different options, compare prices, and consult with builders or architects to identify the best materials that align with your taste and budget.

Building Regulations

Complying with building regulations is essential for any construction project in the UK. Costs associated with obtaining planning permission, building regulations approval, and other legal requirements should be factored into your budget, and importantly, a contingency budget of 5% should be set aside for any additional building regs requirements that the inspector may ask for on site, that have not been identified or have been assumed on drawings. 

Engage with building control early in the planning phase to understand the regulations specific to your area and estimate the associated costs accurately.

Planning and design fees

You will need to retain an architects, structural engineer, and builder for your extension. While their expertise ensures the quality and safety of your extension, their fees can significantly impact your budget.

Obtain multiple quotes from professionals and compare their services and charges. As a rule of thumb expect to spend 7%-10% of the build budget on professional planning and design fees.

Build Management

Your single story extension cost can be optimised with effective oversight on the build phase. Poor project management can lead to delays, mistakes, and additional expenses. If you have the skills and time, you may choose to manage the project yourself, but it is crucial to evaluate your capabilities objectively. Hiring a competent project manager or a reputable contractor can ensure efficient coordination, timely completion, and cost control.


To sum up then, controlling and planning for single storey extension cost in the UK involves careful planning, research, and decision-making. Consider the size, design complexity, location, and site conditions when determining the scope of your project and make fact-based decisions on materials choice, obtain the necessary planning consent. Retaining the services of a professional architecture firm will help you avoid the pitfalls, as will this must-read handbook on how to extend your home and get it right first time, available on Amazon for £9.99.