HOW TO PLAN A HOME EXTENSION: A STEP-BY-STEP GUIDE FOR HOMEOWNERS

Thinking about extending your home? Whether you are dreaming of a light-filled kitchen, a cosy family room overlooking the garden, or a calm workspace away from the chaos, planning a home extension can be exciting. But it can also feel overwhelming if you are not sure where to start.

As architects who work closely with UK homeowners, we have helped many families create spaces that not only look beautiful but feel wonderful to live in. So we have put together this friendly, easy-to-follow guide to help you plan your home extension with confidence.

1. Start with Your Why: Your Vision for the Space

Before diving into planning permission and costs, spend some time thinking about how you want your home to feel and function.

Ask yourself:

• What is not working in your home right now?

• Do you need more space, more light, or simply better flow?

• Is the goal to create a space for family, entertaining, working or all three?

• How do you want the extension to connect with your garden?

Instead of thinking "we just need an extra room", imagine how you want to live in that space. Think about morning coffee light, family dinners, or open doors to the garden in summer.

2. Set a Clear and Realistic Budget

Extensions in the UK typically range from £1,800 to £3,500 per square metre, depending on location, specification and complexity. In cities like London or for high-end finishes, costs can reach up to £4,000 to £4,500 per square metre.

But remember, the build cost is not the full picture.

You will also need to allow for:

Cost Type	What to Consider
Architect Fees	Design, drawings, planning and coordination
Structural Engineer	Required for beams, openings, lofts and more
Planning or Lawful Development Fees	If approvals are needed
Building Control	Usually around £500 to £1,000
VAT	Often forgotten but essential to include
Finishing and Interiors	Flooring, lighting, storage, cabinetry, furniture

It is wise to include a contingency budget of 10 to 15 percent for any surprises.

3. Do You Need Planning Permission?

In the UK, not all extensions need full planning permission. Some fall under Permitted Development (PD) which allows certain types of extension without a full application.

Permitted Development often covers:

✔ Single-storey rear extensions within size limits

✔ Use of matching materials

✔ Certain rear-facing loft conversions

✔ Some side extensions

But you should still apply for a Lawful Development Certificate to confirm it is legal and safe for future selling.

You will need full planning permission if:

• You are in a conservation area or listed building

• The extension is visible from the road

• You want to exceed size limits or alter the roofline significantly

A good architect will help you choose the right route and even design around planning limits to maximise space.

4. Work with an Architect (More Than Just Drawings)

Many people think architects only provide building plans, but the real value lies in bringing your space to life.

• A good architect will help you:

• Unlock clever design solutions you had not considered.

• Bring more natural light and better flow into the space.

• Connect indoor living to the garden beautifully.

• Handle planning drawings and applications.

• Coordinate engineers, builders and consultants.

• Create 3D visuals so you can imagine the space before it is built.

At Nua, we focus on designing for how you live, not just how it looks.

5. Prepare Technical Drawings and Building Control

Once the concept design is agreed, your architect and structural engineer move into the detail stage.

This includes:

✔ Structural drawings for beams, foundations and support

✔ Building Regulations drawings for fire safety, drainage and insulation

✔ Building Control approval

These documents allow your builder to price accurately and ensure everything is built safely and legally.

6. Finding and Choosing the Right Builder

When you are ready for quotes, make sure all builders receive the same drawings so you can make fair comparisons.

Tips for choosing wisely:

• Always get at least three itemised quotes

• Ask for references or examples of past extensions

• Make sure they are insured and offer written contracts

• Look for clear communication, not just the lowest price

  
  

The best builder is often the one who communicates well, understands your vision, and is organised. Not always the cheapest.

7. What Happens During Construction?

Once everything is approved, building can begin. While every project is different, most home extensions follow these stages:

1. Site preparation and foundations

2. Structure and walls

3. Roof, doors and windows

4. Plumbing, electrics and insulation

5. Internal finishes such as plastering, flooring, kitchen and joinery

6. Final approvals and snagging

   
   

If required, your architect can stay involved during construction for site visits, builder coordination and quality checks.

8. Final Sign-Off and Enjoying Your New Space

Once your extension is complete, you will receive your Building Control Completion Certificate and proof of planning compliance if applicable.

Keep these safe for future selling or refinancing.

And then, it is time to enjoy your beautiful new space. Whether it becomes the heart of family life, a peaceful escape or a space that brings everyday joy, it is yours to live in, not just look at.

Final Thought

Extending your home is not just about adding space. It is about improving your daily life. The right design can change the way you live, feel and connect with your home.

If you are thinking about extending and want to explore ideas, planning or feasibility, we would love to help.

Book a friendly conversation with Nua. No pressure. Just possibilities.