Extending your home is one of the most effective ways to create the space your family needs without the upheaval of moving. Whether it’s a larger kitchen, an extra bedroom, a home office or a more generous living area, a well-designed extension can transform how your home works for you, and add real value in the process.
But for many homeowners, the process feels daunting before it begins. What needs planning permission? How long will it take? What’s it actually going to cost? This guide walks you through the key stages so you know what to expect.
Step One: Work Out What You Actually Need
Before you speak to anyone, it’s worth spending some time thinking about how you use your home now and how you’d like to use it in the future. The best extensions aren’t just bigger, they’re better. A thoughtful brief will help your architect understand not just the space you need, but how it should feel, how it connects to the rest of the house, and how it relates to your garden and outdoor space.
Things to consider at this stage:
- Which rooms are you trying to improve, and why?
- How do you use the spaces you have at the moment?
- Are there any aspects of your current home that frustrate you that an extension could fix?
- What’s your realistic budget, and how flexible is it?
- Do you have a rough timescale in mind?
Step Two: Understand Your Planning Position
Not all house extensions require a planning application. Many single-storey rear extensions can be built under permitted development rights without applying to the council, though this depends on the size, height and position of the extension, and whether any restrictions apply to your property.
Key factors that affect your planning position include:
- Whether your home is in a conservation area, if so, certain extensions that would otherwise be permitted development may require planning permission
- Whether your property is listed, all external and many internal works to listed buildings require listed building consent
- Whether an Article 4 Direction applies to your area, removing some permitted development rights
- The type and style of extension, two-storey extensions, side returns and front extensions almost always require planning permission
Birmingham City Council follows the National Planning Policy Framework (NPPF) and its own Local Plan when assessing applications. The council’s design policies place weight on proposals that respond positively to their surroundings, so the quality of design matters, not just the size.
Step Three: The Design Process
Once you’ve appointed an architect and agreed on a brief, the design process typically begins with a measured survey of your existing home. This forms the basis for all the drawings that follow.
From there, your architect will develop initial concept designs for you to review and refine. This is the creative stage, the point at which the real potential of your project takes shape. Good architects will be honest with you about what’s likely to work both practically and from a planning perspective, rather than simply drawing what you ask for and letting the council refuse it.
When you’re happy with the design, your architect will prepare the formal planning drawings and any supporting documents needed for the application. Depending on the project, this might include a Design and Access Statement, Heritage Statement, or a Daylight and Sunlight Assessment.
The Planning Application Process
A full planning application for a residential extension in Birmingham is typically determined within 8 weeks, though complex or sensitive cases can take longer. During that time, the council will consult with neighbours and any relevant consultees, carry out a site visit, and assess the application against its policies.
Pre-application engagement with the council can be a worthwhile investment for more complex projects, giving you a steer on the principle of your proposal before committing to a full application. Your architect can advise whether this is appropriate for your project.
Building Regulations – A Separate Process
Planning permission (or permitted development) is just one part of the consent process. You’ll also need to comply with Building Regulations, which set standards for the structural, thermal, fire safety and accessibility performance of the building.
Building regulations approval is obtained either through your local council’s building control team or through an approved inspector. Your architect will prepare a separate set of more detailed drawings and specifications for this purpose, different in nature from the planning drawings, which are about the design, appearance and principle of the development.
Finding a Contractor and Managing the Build
Once you have both planning and building regulations consent, you’re in a position to appoint a contractor and start on site. Your architect can help you prepare a tender pack, approach suitable contractors, evaluate quotes and appoint on the right terms.
Having your architect involved during the construction phase, making site visits, reviewing progress and certifying payments, gives you an important layer of protection and helps ensure the building is delivered to the standard you expect.
How Long Does It All Take?
Timescales vary depending on the complexity of the project and how smoothly each stage proceeds, but as a rough guide:
- Design and planning preparation: 4 -10 weeks
- Planning determination: 8 -10 weeks
- Building regulations drawings and approval: 4 – 8 weeks (can run alongside planning)
- Contractor tender and appointment: 4 – 6 weeks
- Construction: typically 10 – 20 weeks for a single-storey extension, longer for more complex projects
From first appointment to moving back into your finished extension, a typical project might span 9 – 18 months in total.
Common Questions
Do I need to tell my neighbours before I start?
If your extension is near or on the boundary with a neighbour’s property, the Party Wall etc. Act 1996 may apply. This requires you to serve formal notice on affected neighbours before work begins. Your architect can advise whether this is relevant to your project.
Can I live in my home during the build?
In most cases, yes, though there will inevitably be periods of disruption, noise and dust. Good contractors will take reasonable steps to minimise this, and your architect can include clauses in the building contract that address working hours and site management.
What if the costs come in over budget?
Detailed drawings and a thorough specification help you get accurate, comparable quotes from contractors. Contingency budgeting, typically 10 – 15% of the construction cost, is always advisable to cover unforeseen issues.
About Brophy Riaz and Partners
Brophy Riaz and Partners are a RIBA chartered architectural practice with more than 28 years of experience delivering residential projects across Birmingham and the West Midlands. The team has guided thousands of homeowners through the extension process, from initial concept through planning, building regulations and construction, and has an in-depth understanding of what works locally.
With over 3,000 completed projects and a genuine passion for well-designed homes, Brophy Riaz and Partners bring both the technical knowledge and the personal care that a project like this deserves.