Extensions are a great way to make money from property.
They increase your square footage and property value.
If your property already has a basement, it’s worth considering extending it.
So, how much does a basement extension cost? How long does it take? And what are the different types available?
Read on to find out.
What is a basement extension?
A basement extension is when you increase the basement’s square footage beneath your house.
The goal is to add more liveable space to your property, which can be in the form of an extra:
- Bathroom
- Bedroom
- Living area.
Or more.
Basement extensions are popular because they avoid sacrificing outdoor areas.
For instance, if you add a conservatory, you may decrease space in your garden.
Remember that there are plenty of hoops to jump through with a basement extension. You may need planning permission.
And you can’t afford to compromise structural integrity, waterproofing, or ventilation.
Part of your house may be out of bounds while the extension is underway.
Different types of basement extension
Full basement extension
This is often described as a regular extension.
If you’ve already got a basement beneath your house, you can extend the entire area, to increase square footage. This might involve adding an extra room.
Basement conversion
This type doesn’t increase the square footage. Instead, you’re converting the basement to change its functionality.
This is useful if your current basement isn’t usable. You’ll thus renovate it to add electricity, heating, and water.
Retrofit basement
This involves adding a basement when it doesn’t already exist. It’s thus more of an extension on the house!
Your contractors will need to dig into the ground to achieve this. And you’ll need to get clear architectural plans outlining how large this will be.
Garden basement
A garden basement is installed under a garden area. This is especially popular in busy cities, where space is limited.
It takes careful expertise to ensure you don’t damage the earth above. If you don’t have a large garden, this basement can’t be too big.
How long does a basement extension take?
Basement extensions usually take between 3 – 6 months on average.
The project takes a long time because of the complicated steps involved. You need to follow the correct procedure and can’t cut corners.
You often need to get planning permission. You’ll then need an architect to ensure it’s designed safely.
Excavation and underpinning are often required at the start of the project. Waterproofing and construction then take a couple more months, as well.
Unforeseen issues could come up during the installation. This pushes your timeline back further. Examples include:
- Poor ground conditions
- Encroachment on neighbours (which might lead to disputes)
- Inability to get materials
- Encountering wild animals.
How much does a basement extension cost?
A typical price for a basement extension in the UK is £100,000.
For smaller projects, you could expect around £75,000. However, for larger projects, £150,000 is not uncommon.
These averages also go higher in London and south-east England. You should factor this in when you’re budgeting.
Most contractors charge for this service based on square footage.
One metre squared of extension costs around £3,500 on average. So, the larger the extension you’re looking for, the more it’ll cost.
There are plenty of other factors that influence price. Some building contractors and architects charge more than others.
And the materials involved make a big difference, too.
Do I need planning permission for a basement extension?
It depends on the situation. You should check, to be sure.
Planning permission is needed when the appearance of your property changes.
For example, if:
- The street view of your house changes due to the extension
- Your house is listed
- You live in a conservation area.
In these cases, planning permission will also be needed.
Converting an existing basement may not need planning permission.
And if you aren’t adding a bedroom or changing the house’s external appearance, you could be fine without it. You should always check though, to be safe.
How does a basement extension impact my property value?
A basement extension makes your house more valuable. This is because it increases square footage.
And it may also push up the number of bedrooms, bathrooms, or living areas in your house.
When it’s carried out well and adds plenty of square footage, your house value could increase by around 20% on average. Smaller extensions typically have a 10% or 15% increase in house value.
You should manage your costs throughout the extension process. Project how much value you expect to add and get an expert’s opinion.
You don’t want to spend more on the extension than the value it’ll add to your house.
Is a basement extension always possible?
No, basement extensions aren’t always possible. You should get an expert to visit your property for personalised guidance.
One of the reasons it may be impossible is because of ground conditions.
There could also be planning restrictions, such as if your property is listed.
Flood risks may make it impossible for a basement extension to be built.
And if protected animals or plants are on the nearby earth, this could also limit you.
