Domestic House Extensions
At TNM Architecture, we appreciate that your home is one of your most valuable assets, and the idea of altering it can sometimes feel overwhelming. That’s why our approachable, hands-on service is tailored to support you through every stage of the extension process with clarity and confidence.
We’re passionate about helping you unlock the full potential of your home — whether that means rethinking the layout, enhancing natural light, or creating much-needed extra space. We work closely with you to make the most of your budget and to ensure a smooth, well-managed project from concept to completion.
Alongside our architectural expertise, we also offer guidance on other likely costs — such as Structural Engineer input and Local Authority fees for Planning and Building Control — so you can plan ahead with no surprises.
How much does a house extension cost to
Design / Build ?
Each property/ site location and client budget is unique so no project is ever the same, your requirements as a potential client may vary and most importantly your build budget will dictate what can be achieved. Our guideline fee schedule below gives typical examples.
Can we build the extension under Permitted Development Rights?
You can perform certain types of work without needing to apply for planning permission. These are called "permitted development rights". Keep in mind that the permitted development rights which apply to common projects for houses do not apply to flats, maisonettes or other buildings. There are also different rules if the property is a listed building.
You should always contact your Local Planning Authority and discuss your proposal before any work begins. They will be able to inform you of any reason why the development may not be permitted and if you need to apply for planning permission for all or part of the work.
A link to the planning portal's useful guide is below :
Home improvement projects | Planning Portal
Timescales
Typically, Local Authorities aim to make a decision within 8 weeks from the date your planning application is registered. However, please be aware that timescales can vary, particularly in light of ongoing pressures on council services.
Fees
Each project is unique, and we assess all general enquiries on an individual basis. For a clearer idea of costs tailored to your specific requirements, please get in touch with our office — we’ll be happy to help.
'Myself and my wife wanted to personally thank you and your team for all your help. You have helped create for us our dream home really appreciate it. We absolutely love it. Thank you.'