Planning an Extension: Where Do I Start?

Starting an extension can feel like a big step, especially if you have never done it before. The early stage is often where people feel most uncertain, not because the process is impossible, but because they are trying to answer too many questions at once. The best place to begin is with the basics: what you want to achieve, what the property can realistically accommodate, and what the likely planning route may be.

Start with what you are trying to achieve

Before looking at plans, applications, or styles, it helps to step back and define the purpose of the extension. This gives the project direction and helps avoid making decisions too quickly.

• What is not working in the house now?
• Do you need more space, or a better layout?
• Which room or part of the house matters most?
• Are you trying to improve family living, storage, light, or flexibility?
• Is this a short-term improvement or a long-term investment in the home?

These questions may seem simple, but they are often more useful than starting with size. A larger extension is not always a better one. In many cases, the real improvement comes from better flow, more usable space, and a layout that suits how you actually live.

At this stage, it is also worth separating what is essential from what would simply be nice to have. A clear list of priorities will make every later decision easier.

Understand the property before you plan the extension

The next step is to look carefully at the property itself. An extension does not exist on its own. It has to work with the house, the site, and the surrounding context.

Start with the basics:

• the type and age of the house
• the amount of outdoor space available
• how close the neighbours are
• where the current rooms sit
• how the garden, side access, and boundaries are arranged

Some houses have obvious opportunities for extension. Others are more restricted by layout, plot shape, previous additions, or neighbouring relationships. What looks simple at first can become less straightforward once those factors are considered.

This is also the point where planning history can matter. If the property has been extended before, or if previous applications have been made, that may affect what is possible now.

You do not need to know every detail at the start, but you do need a realistic understanding of the house and site before deciding what direction to take.

Think about feasibility before thinking about submission

A common mistake is to think the first step is submitting something to the council. In reality, the first useful step is usually checking feasibility.

Feasibility means asking whether the extension is likely to work in practical and planning terms before committing to a full direction. It is an early sense check.

This usually involves questions such as:

• Is the size of extension realistic for the site?
• Will it sit comfortably with the existing house?
• Is it likely to create obvious neighbour issues?
• Is the proposal proportionate, or is it trying to do too much?
• Does it fit the broad budget range?

This stage is valuable because it filters out weak ideas early. It allows you to focus on what is likely to be sensible, not just what might fit on paper.

A feasibility-led approach also tends to produce better projects. Instead of forcing one solution too early, it gives you a chance to test options and decide what genuinely improves the house. S2bstudio have a track record of 100% planning approval, assisting clients in the navigating the planning application of what is most likely to be acceptable by council but also maximizing clients need for space.

The Likely planning route

Once the brief is clear and the property has been assessed, the next early question is the likely planning route.

For many householders, this comes down to usual 2 main possibilities:

Permitted development

Some extensions may fall within permitted development rights, subject to limits and conditions. This route can apply to certain forms of householder extension, but it should not be assumed without checking the specifics of the property and proposal.

Planning permission

If the extension falls outside permitted development rights, or if those rights do not apply, planning permission may be required.

At the starting stage, you do not need to become an expert in every rule. What matters is understanding that there may be more than one route, and that the correct route depends on the property and the proposal.

This is where early professional advice can be useful. A short review of the likely route can prevent time being wasted on the wrong assumptions. Our feasibility checker assist in this section.pproval, assisting clients in the navigating the planning application of what is most likely to be acceptable by council but also maximizing clients need for space.

What usually happens next

Once you have a clear sense of what you want to achieve, the next step is usually a feasibility review based on the actual property. That should help confirm what type of extension is realistic, what the likely planning route may be, and whether the project is aligned with your priorities and budget.

From there, the project can move into early design development and the appropriate planning route. That is usually the point where the process starts to feel more structured and less uncertain.

A good start is about making the right early decisions with enough clarity to move forward confidently.

This article is intended as general guidance. Requirements vary depending on the property, site constraints, scope of works, and local authority considerations, so project-specific advice should always be sought before proceeding.