Why build a basement?

Basement construction is a great option for anyone looking to extend their home. Many people consider building up or out when they think about home extensions. If that’s you, why not consider the prospect of building down?

Building a basement under an existing house in the UK may be a better option for you if you’re facing issues getting planning permission. You might also have limitations when it comes to potential to expand out or up with your property.

In this guide, we’ll take a look at some of the most compelling reasons to build a basement. Plus, some handy tips on things like the average costs of a basement construction project, and how to get started.

What could a basement be used for?

A basement can be hugely useful in many different ways. For starters, you can significantly increase your living space, especially if you build a basement across the whole footprint of your property.

You could use your new basement for all kinds of exciting purposes. For example, you could create a games room or a home cinema, or turn it into a wine cellar or a sauna. You can use your basement as a gym or fitness suite or even an underground space to park your car. If you’re feeling really ambitious, why not convert your basement into a swimming pool?

One of the most common uses for a brand new basement is for extra accommodation, acting as a guest room. If you have enough space, you could even create a whole apartment in the basement with its own separate entrance. You can rent out this space, or use it as a granny annexe for family members.

And what about a home office? At a time when many of us are working remotely, a home office in the basement could be super useful.

Basement construction – pros and cons

To help you decide whether building a basement is a good move for you and your family, let’s take a look at the pros and cons of building down.

Advantages of building down

• A good way to add extra living space when there’s no land or potential to build up or out – without losing any external space.
• Can potentially add value to your home – especially in high-value areas.
• Underpinning can stabilise an old building.
• Waterproofing can help to dry out the whole house.
• Insulation in the basement can make the whole home more energy efficient.
• Basements are adaptable spaces, which can free up rooms in other parts of the house.
• It’s possible to create self-contained basements – if you’re interested in creating a granny annexe or renting out the space.

Drawbacks of basement construction

• Basement construction is often complex, disruptive, noisy and messy and like any construction work, there’s always the chance of unforeseen problems.
• It can be a challenge to get enough natural light and ventilation into the basement.
• You may need to spend money on a new access route if safety is a concern.
• You’ll need to get planning consent and possibly a party wall agreement too.
• Waterproofing can be another obstacle, requiring additional expense and an annual inspection of the drainage system.
• The cost to build a basement can be high, and there’s a chance you won’t recoup the expense when you sell your home.

How much does it cost to build a basement?

Building a new basement can be quite a complicated project, as there are lots of factors to consider.

Basement construction costs can depend on how suitable the ground and site is for a basement. Plus, how easy it is to access, excavate and remove soil from the ground. You’ll also need to think about how the foundations will be built, waterproofing and fit-out.

All things considered, it can cost anywhere between £1,500 and £3,000 a square metre to build a basement. Find out more about the costs to build a basement here.

How much does a basement add to home value?

In general, adding an extra room can add as much as 20% to your property value, according to the Homeowners Association.

However, the cost to add a basement is nearly double that of converting a loft, so there’s a chance that you may not see your money back. However, it can make sense in high-value areas, where property prices are higher, and where land space for extensions is limited.

A good way to maximise the value of your basement room is to make sure it has a decent ceiling height and as much natural light as possible. For example, using a skylight, light tunnels or carefully placed window.

FAQs

Which tradespeople do I need to help me with my basement construction?

You’ll need a qualified and experienced builder, ideally one specialising in building basements. Remember that basements can sometimes be difficult and complicated projects, so you need a trusted, highly skilled builder on your team.

You may also need the services of an architect or building engineer, plus a damp proofing or waterproofing specialist. You’re likely to need an electrician for power and lighting, and a painter/decorator to get the finish perfect.

How long does building a new basement take?

It varies, but you can usually expect the job to be complete within a few months.

Can I extend the basement beyond the footprint of the house?

You can absolutely extend your basement beyond the footprint of your home, provided you own enough land and the ground conditions are right.

Do I need planning permission for a new basement?

You’re likely to need planning consent for a new basement in certain circumstances. For example, if the excavation constitutes major works, or your new basement alters the exterior appearance of the house significantly. If you’ll be creating a separate entrance to the basement or adding a lightwell, you’ll almost certainly need to put in a planning application.

What building methods are best for a basement?

The construction method used for building a basement typically depends on the budget, soil type and conditions of the site. The different methods include precast waterproof concrete panels, brick and blockwork, and ICF (insulated concrete formwork) or shuttered concrete.

How do you waterproof a basement?

To find out about waterproofing a basement and the costs involved, check out our guide to basement waterproofing costs.