While less common in the UK than loft conversions, basement conversions can be a brilliant way to add space to a house without extending its footprint.
That said, when it comes to how to convert a basement, things can be a little more complicated than with lofts or extensions. Not only do you need to consider the practical aspects, such as waterproofing and getting light into the new space, but you also need to ensure the whole project is carried out safely and meets certain criteria.
Basement building regs can be a little confusing, which is why we reached out to the experts to bring you all the advice you need to ensure your own project sails through the approval process and becomes a valuable addition to your home.
Do you need building regs approval to convert a basement?
If you are carrying out a conversion for basement ideas that will create a new habitable space, you will definitely require building regulations approval.
‘If you’re planning to turn your basement into a habitable space, you will need building regulations approval,’ confirms Paula Higgins, CEO of HomeOwners Alliance. 'But it's not just red tape. These rules make sure the space is structurally sound, properly ventilated and insulated, damp-proofed, and has safe fire escape routes.
'Without approval, the conversion won’t be legally recognised, and you could face problems when you sell or insure your home,' continues Paula. 'Basements are particularly prone to damp and structural issues, so building regulations are there to protect you.'
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Which building regs apply to basement conversions?
The building regulations are a set of mandatory criteria relating to the design and construction of new buildings in England and Wales, and include extensions, conversions and alterations. They are there to ensure buildings are safe, energy efficient and healthy to spend time in.
'Getting building regulations approval is a legal requirement, not a suggestion, and this applies regardless of whether planning permission is required,' picks up Farook Member, director and home improvement expert at QS Supplies. But which of the regs apply?
'Building regulations have various parts that apply to a basement conversion,' explains Farook, who goes on to list the most relevant.
- Structural (Part A): Relevant for any structural work, such as underpinning.
- Fire safety (Part B): You may need to provide safe escape routes and fire doors.
- Ventilation (Part F): Essential in preventing damp and condensation.
- Thermal Insulation (Part L): Walls, floors and ceilings need to be to current thermal performance standards.
- Sound Insulation: If your basement is under or adjacent to a habitable room.
- Drainage and damp proofing (Part C): Generally includes waterproofing and sump pump system.
Farook Member is the director of QS Supplies and a seasoned expert in the home improvement and bathroom industry. With over three decades of experience, Farook has been at the forefront of innovation and quality since founding QS Supplies in 1990.
What kind of building regs application do you need for a basement conversion?
Just as with building regulations for extensions, there are several different types of application that you can make for basement conversions, with each being suitable for various types of projects.
The two most relevant to basement conversions are a 'Full Plans Application' or a 'Building Notice'.
'For most basement projects, the best route to obtain building regulations approval is with a Full Plans Application,' advises Paula Higgins. 'This involves submitting drawings for approval before you start, so you can move forward knowing your design meets the rules.
'While you can choose a Building Notice, which allows you to begin work without approved plans, this is generally unsuitable for basement projects because of the complexity involved.'
How much does a building regs application cost?
Another basement conversion mistake is to forget to factor in a building regulations application into your overall basement conversion costs, although the exact cost will depend on your local authority.
'As an example, Calderdale Council charges around £330 for a basement conversion up to 100m² under a Full Plans application,' explains Paula Higgins. 'That includes the plan checking and inspection stages. Other councils may charge more, and many homeowners find fees fall between £500 and £1,000 depending on the scale of work.
'The best advice is to check your own council’s building control fee schedule before you begin.'
'This is only the cost of the application and does not include structural engineering and professional fees,' points out Farook Member.
What other permissions might you need to convert a basement?
It isn't just building regulations approval that you need to arrange before converting your basement – you might also need planning permission.
'In some cases, a basement conversion can fall under permitted development rights, particularly if you are converting an existing cellar and not making any external changes,' points out Paula Higgins. 'However, if you are excavating a new basement, adding a lightwell or changing the external appearance of your home, you are more likely to need planning permission.
'Rules are stricter if your home is listed or in a conservation area,' continues Paula. 'Because the criteria can vary, the best thing to do is call your local council’s planning department before you begin, so you know exactly what applies to your property. You can find your local planning authority through the Planning Portal.
If you live in a listed property, you will need to apply for listed building consent in order to convert your basement.
Do you need a Party Wall Agreement for a basement conversion?
If your conversion will affect any party walls, it will be necessary to familiarise yourself with the Party Wall Act.
'If you are excavating close to or beneath a shared wall, the Party Wall Act will apply,' advises Paula Higgins. 'That means you’ll need to formally notify your neighbours and may need a Party Wall Agreement in place before you can start work.
'Basement conversions are particularly disruptive, so it pays to get things right from the start,' adds Paula. 'Find and speak to a party wall surveyor who can explain what's needed, guide you through the process and make sure the project goes smoothly. The last thing you want is a dispute with a neighbour.'
FAQs
What is the difference between a basement and a cellar?
The terms 'cellar' and 'basement' are often used interchangeably in the UK, leading to some confusion in terms of how they differ.
In truth, they are very similar, however there are a few key differences.
Both sit either partially or entirely beneath the house, but cellars tend to be smaller, used for storage or housing plant only and are not usually suitable as habitable spaces.
Basements, on the other hand, are usually better ventilated and often feature natural light sources, making them more suitable for conversion into habitable spaces.
Mulling over the idea of a basement conversion? This is not always a straightforward project so be sure to look into all the things you need to know before converting a basement first.
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