What are the steps of building an extension

We've put together this guide to help you understand what's involved in extending your home, from initial planning to final completion.

Steps of building an extension:

Planning permission and permitted development 

Party wall matters 

Building regulations 

Finding your team 

Design phase 

Breaking ground 

Build process 

Finishing up/documentation

Planning permission and permitted development

First things first - check whether you need planning permission. Many extensions fall under 'permitted development rights', particularly if you're extending to the rear of your property. However, if you live in a conservation area, listed building, or your plans are ambitious, you'll likely need full planning permission from your local council.

Party wall matters

If you're building on or near your neighbour's boundary, you'll need to sort out a Party Wall Agreement. Give yourself at least two months for this process. Your neighbours can either consent to the works or request a Party Wall Surveyor. Even if relations are friendly, get everything in writing.

Building regulations

Unlike planning permission, Building Regulations approval is mandatory. You'll need detailed drawings that comply with current regulations covering everything from foundations to energy efficiency. You can either submit a Full Plans application or use Building Notice. Most architects recommend Full Plans as it provides more certainty.

Finding your team

You'll need several professionals:

• An architect or architectural technologist for drawings

• A structural engineer for calculations

• A main contractor (builder)

• A building control officer or approved inspector

The design phase

Your architect will draft initial plans, considering things like:

• The impact on your Council Tax band

• Whether you need a bat survey (more common than you'd think!)

• If your drain run needs diverting (which requires approval from your local water authority)

• The best materials to match your existing property

Breaking ground

Once the paperwork's sorted, work begins with foundation trenches. Your building inspector will want to check these before any concrete is poured. Be prepared for the Great British weather to cause delays - winter builds often take longer than summer ones.

The build process

The speed of the build depends on various factors, but typically:

• Foundations and drainage: 1-2 weeks

• External walls and roof: 3-4 weeks

• First fix (electrics, plumbing, windows): 2-3 weeks

• Plastering and second fix: 3-4 weeks

• Finishing touches: 2-3 weeks

Managing the build

Keep your neighbours sweet: a box of chocolates and regular updates go a long way. Your builder should provide skips and keep the site tidy. They'll need somewhere to store materials and probably access to your loo - sort these logistics early on.

Practical considerations

Consider your living arrangements during the build. If you're extending your kitchen, you'll need to set up a temporary one - perhaps in your dining room. A microwave, kettle, and camping stove can help you survive the disruption.

The money bit

Budget carefully for:

• Professional fees (typically 10-15% of build cost)

• VAT at 20% on everything except planning fees

• Building control fees

• Party Wall Surveyor fees if needed

• Skip permits if you're in a controlled parking zone

• Materials (prices have been volatile recently, so get firm quotes)

Always keep a contingency of 10-15% - you never know what's lurking beneath your floorboards or behind your walls.

Finishing up

Before your builder leaves site, you'll need:

• Building Control completion certificate

• Any electrical certificates (Part P certification)

• Gas Safe certificates if applicable

• Guarantees for windows, doors, and any specialist materials

• FENSA certificates for windows

Keep all these documents safe because you'll need them when you eventually sell.

The bottom line

Building an extension in the UK requires patience and attention to detail with paperwork, but the end result is worth it. Most projects take 3-6 months from first breaking ground to completion, depending on size and complexity. Choose your team carefully, keep communication channels open, and remember - an extension that's done properly will add significant value to your home while giving you that extra space you need.

A final tip is to join local Facebook groups or forums where people share their extension experiences. The advice from those who've recently been through the process is invaluable, especially regarding local builders and suppliers.

How we can help you

While building an extension involves many steps, you don't have to navigate them alone. At Anyo Ltd, we handle the entire process from initial planning to final decoration. Our experienced team can guide you through planning permission, manage Party Wall agreements, and coordinate all aspects of construction. With over 20 years of experience in UK home extensions, we pride ourselves on high-quality craftsmanship and attention to detail. We offer free initial consultations to discuss your ideas and provide detailed quotes with no hidden costs. Whether you're planning a simple kitchen extension or a complex multi-room addition, we will ensure your extension is completed on time, within budget, and to the highest standards. Contact us today to turn your extension dreams into reality.