6 Things To Do Before Remortgaging to Pay for a Home Extension

An extension can completely change how you use your home. Whether you’re dreaming of a bigger kitchen, an extra bedroom, a home office or simply more space for a growing family, extending can sometimes make more sense than moving.

We’ve known for a while that we wanted to extend our house. A double story extension would be the dream, but it’s outside of our budget. So a single story one is our plan. It will give us two new rooms downstairs and then allow us to reconfigure the bedrooms upstairs.

But before you get carried away there’s one very important thing to think about: how are you going to pay for it?

If your plan is to remortgage and release some of the equity in your home to fund the extension, there are a few things worth doing before you get to the mortgage application stage.

The exact process will vary depending on your circumstances, your lender and the type of work you’re planning, but these are the first six things I’d do.

1. Speak to your mortgage adviser first

Before spending money on architects, drawings or planning applications, I’d start with a mortgage adviser.

You don’t necessarily need to make a formal mortgage application at this point. Instead, you’re looking for a very rough idea of whether borrowing additional money could be realistic and what that might mean for your monthly mortgage payments.

This could potentially make or break the whole extension idea.

There’s no point designing your dream extension if you discover afterwards that the additional borrowing you need isn’t affordable or isn’t likely to be available to you.

Your mortgage adviser can look at your current mortgage, income, existing commitments and other relevant circumstances to give you an indication of what additional borrowing might look like. They should also be able to give you a rough idea of how much your monthly repayments could increase.

Remember that this is only an early indication. Your circumstances could change, mortgage rates can change and the eventual amount a lender is willing to offer will depend on its affordability and lending criteria.

But at this stage, you’re trying to answer a simple question: Is this extension financially worth exploring? If the answer is yes, you can move on to the next steps with a little more confidence.

I did this stage back in August, and realistically I wish I’d started the process earlier.

2. Speak to an architect about your ideas

Once you have a rough idea of what you might be able to borrow, it’s time to start turning your ideas into something more realistic. This is where an architect can help.

You might have a very clear idea of what you want, or you might simply know that you need more space and have no idea what the best solution is. An architect can talk through your requirements, the existing layout of your home and what you want to achieve. They can also help you understand what’s realistically possible.

Your dream extension might look amazing in your head, but your property, boundaries, access, structure or local planning requirements could all affect what you can actually build. For example our architect told us that a tree in our garden would need to be removed as the roots would be too close to the proposed extension. And this is something we can look at sorting asap.

At this stage, it’s worth being open about your budget too. There’s no point designing something that costs significantly more than you’re comfortable borrowing.

This was a stage I didn’t know about. I went straight to a builder for a quote and it was them that said had we got the details from an architect. So we had an architect come out in August to chat through our ideas and give us some advice.

3. Get a home survey and technical drawings done

Before you can properly price the project, you’ll need to understand your existing property and have the proposed extension documented. This is where a home survey and technical drawings come in.

A survey can give you a better understanding of the existing building and highlight things that could affect your plans. Technical drawings then turn your ideas into detailed plans that can be used for the next stages of the process.

This is one of those points where you might start realising that an extension is more complicated than it initially seemed. That’s not necessarily a bad thing. Finding out about potential issues early is much better than discovering them once builders are already on site.

Your drawings will also become incredibly important when you start talking to builders because you’ll want everyone quoting for the same thing. Without detailed drawings, you could end up comparing quotes that aren’t actually like-for-like.

We had the architect come out to us in early September to do all the measurements, and then we had our drawings finalised by the end of the month.

4. Apply for planning permission

Once you have your plans, you’ll need to establish whether your extension requires planning permission and, if it does, submit an application. Not every extension will necessarily need a full planning application, as some work may fall under permitted development rights, depending on the circumstances. However, don’t assume that your particular project qualifies. It’s worth getting the appropriate professional advice and checking the rules that apply to your property.

If planning permission is required, you’ll need to factor the application process into your timeline. This is another reason why I wouldn’t rush into getting builder quotes based purely on an idea you’ve had. You want to know what you’re actually allowed to build.

Your architect or other professional involved in the project can help you understand what permissions and approvals may be needed.

And remember that planning permission isn’t necessarily the only consideration. Building regulations and other requirements may also apply to the work.

Our architect let us know that we would need to get planning permission and they can support with that. So that’s our next step.

5. Get quotes from builders

Once you have your drawings, you can start approaching builders for quotes. This is where the project starts to become much more real. And potentially much more expensive than you first imagined!

Having detailed drawings should make it easier for builders to understand exactly what you’re asking them to price. Try to get more than one quote so you can compare your options. But don’t automatically go for the cheapest number.

Look at what’s included, what’s excluded and whether the quotes are genuinely comparable. For example, one builder might include certain finishes, fixtures or groundwork while another might not. And make sure you ask questions if something isn’t clear.

It’s also worth thinking about timescales, availability, previous work and recommendations rather than looking at the price alone. The aim is to get a realistic idea of what the extension is actually going to cost.

And this is important because now you can take that figure back to your mortgage adviser.

6. Go back to your mortgage adviser and apply

Now you’ve done the groundwork.

You knowwhat you want to build, you’ve got your drawings, you’ve dealt with planning where necessary and, most importantly, you have actual builder quotes.

This is when I’d go back to the mortgage adviser.

Rather than saying, “I’d like to borrow roughly £X because I think that’s what the extension might cost,” you can now have a much more informed conversation. You’ll know what the project is expected to cost and can discuss how much additional borrowing you might need.

Your mortgage adviser can then look at your circumstances and the available mortgage options and help you understand what the next steps are.

If everything stacks up, you can move forward with the formal mortgage application.

It’s worth remembering that the lender will still need to carry out its own checks. Getting an early indication from your adviser doesn’t guarantee that you’ll ultimately be approved for the amount you’re hoping to borrow.

Don’t skip the financial reality check

It’s incredibly easy to get excited about an extension. You start imagining the new kitchen, the extra living space or finally having somewhere to put all the things currently taking over your house.

But an extension is a major financial commitment, so I think it’s worth doing the financial reality check before getting too far into the process.

If the rough numbers don’t work, it’s better to find that out before spending money on surveys, drawings and planning applications.

And even if the numbers do work, remember that building projects can come with unexpected costs. Having some contingency available is sensible rather than borrowing or budgeting right up to the absolute maximum you can afford.

The process in simple terms

If you’re thinking about remortgaging to fund an extension, the rough order I’d follow is:

Mortgage adviser → architect → survey and technical drawings → planning → builder quotes → mortgage adviser and application.

It might feel tempting to jump straight to an architect because that’s the exciting part where your ideas start becoming real.

But knowing your rough borrowing capacity first can help you set realistic expectations from the beginning.

The aim isn’t to have every detail worked out before you speak to anyone. It’s to build up the information gradually, so that by the time you apply for the additional borrowing, you have a much clearer picture of what you’re building, how much it’s going to cost and what that could mean for your finances.

And if the numbers don’t work? Finding that out early could save you a lot of time, money and disappointment.