Thinking about extending your home? Before you start calling builders and asking for prices, there are a few things worth understanding first.

An extension is a significant investment, and the decisions you make before construction starts can have a big impact on your final cost, timescale and how well the finished space works for your family.

Here are nine things we think every homeowner should know before starting an extension.

 

 

1. The cheapest quote isn’t always the cheapest project

It can be tempting to choose the lowest builder’s quote, particularly when you’re looking at a substantial investment.

However, a lower initial price doesn’t necessarily mean you’ll spend less overall.

Quotes can vary depending on exactly what has been included. One builder might include items such as flooring, kitchen fittings, lighting, drainage and decorating, while another may have excluded them.

This is why it’s important to compare quotations carefully and make sure you’re comparing like for like.

A good set of drawings and a clear specification can make this much easier because your builders are pricing the same project.

 

 

2. Your drawings need to be right before you start getting builder quotes

Your drawings aren’t just something you need for planning permission. They form the basis of the project you’re asking your builder to price.

If you make significant design changes after receiving quotations, your original prices may no longer be accurate.

Getting the design properly considered before approaching builders can help you understand exactly what you’re asking them to build.

It also gives you an opportunity to think about things such as:

• How your family will use the new space
• Where furniture will go
• Natural light and window positions
• Kitchen and bathroom layouts
• Storage
• Heating
• Lighting
• Doors and access
• How the extension connects with the existing house

The more decisions you can make before construction starts, the fewer surprises you’re likely to encounter later.

 

 

3. Planning permission isn’t the only approval you may need

Planning permission is often the first thing homeowners think about, but it isn’t the only consideration.

Depending on your project, you may also need Building Regulations approval, structural calculations and potentially other agreements or consents.

For example, if your proposed extension is close to or over a public sewer, you may need to consider a Thames Water Build Over Agreement.

There can also be additional considerations if you’re working close to a boundary or your project affects neighbouring properties.

Understanding these requirements early means you can factor them into your design, budget and programme rather than discovering them once work has already started.

 

 

4. Structural work can have a significant impact on your budget

Opening up the back of a house, removing walls or creating large areas of glazing can transform how a home feels.

But these changes can also involve significant structural work.

Steel beams, foundations, drainage alterations and other structural requirements all need to be considered when costing an extension.

This is one reason why a rough price based simply on the size of an extension can be misleading.

Two extensions with exactly the same floor area can have very different construction costs depending on the existing property, design and structural requirements.

 

 

5. The design needs to work for how you actually live

It’s easy to focus on adding square metres and forget about how the space will actually be used.

The best extension isn’t necessarily the biggest one you can build.

Think about how your family currently uses your home and what isn’t working.

Perhaps you need a larger kitchen, somewhere for the children to do homework, better connection to the garden, more storage or a separate utility space.

Good design should solve those problems rather than simply adding another room.

It should also consider how the new space connects with the rest of your home.

 

 

6. Small changes can become expensive once you’re on site

Moving a door by a small amount during construction might sound insignificant.

Changing a window, relocating a radiator or adding additional sockets might also seem like relatively minor requests.

But once work has started, changes can involve additional labour, materials and potentially changes to other parts of the project.

This is why it’s worth spending time on the design before construction begins.

A well-considered design isn’t about taking away flexibility. It’s about making the important decisions while changes are still relatively straightforward.

 

 

7. Make sure you understand exactly what your builder’s quote includes

One of the most important things you can do before choosing a builder is understand what’s actually included in the quotation.

Ask questions such as:

• Are foundations included?
• Is drainage included?
• Are structural steels included?
• Is plastering included?
• Are flooring and decorating included?
• Is the kitchen included?
• What about appliances?
• Are light fittings included?
• Is waste removal included?
• Are external works included?

There isn’t necessarily a right or wrong answer to these questions. The important thing is knowing what you’re paying for.

A detailed quotation makes it much easier to understand your likely overall project cost.

 

 

8. Choosing your builder before the design is finished can cause problems

It can feel like the logical first step is to find a builder and ask them what they think the project will cost.

In some cases, builders can provide useful early guidance. However, if the design isn’t sufficiently developed, it’s difficult for anyone to give you a reliable project price.

The builder needs to know what they’re actually being asked to build.

That’s why we recommend getting the design and technical information sufficiently developed before committing to a construction price.

It gives you a much clearer basis for comparing builders and making decisions.

 

 

9. Your budget should influence the design from the beginning

Perhaps the most important thing your builder won’t necessarily tell you is that your budget needs to be considered before you fall in love with a design.

It’s much easier to adjust a design on paper than it is to remove expensive elements once construction has started.

That doesn’t mean you have to design the cheapest possible extension.

It means understanding what you can realistically achieve with your budget and making informed decisions about where to invest.

For example, you may decide that large areas of glazing are particularly important to you, while other elements can be simplified.

Good design isn’t just about making a house look beautiful. It’s about making sure the project works financially as well as practically.

 

 

So, what should you do before speaking to a builder?

Before you start collecting quotations, it’s worth taking a step back.

Think about what you want to achieve, what isn’t working in your current home and what you’d realistically like to spend.

Then get some professional advice on what’s possible.

 

At Fluent Architectural Design Services, we help homeowners through the early stages of their projects, from understanding what’s possible with their property through to design, planning, Building Regulations and pre-construction support.

We can look at your property, discuss your ideas and help you understand the likely route forward before you commit to a builder.