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Is My Property Suitable For A Basement Conversion?

A basement conversion can be a massive project to undertake. So, before delving into a basement conversion, you need to make sure that it is a realistic venture for your property.

Whether converting your basement from a cellar or storage room to a kitchen, study, lounge, or bedroom or excavating the ground beneath your home to create a brand new basement space, we highlight some of the key factors you need to consider to determine whether your property is suitable for a basement conversion.


Building Access

Does your property have sufficient access on-site for builders to remove soil and waste, deliver tools, and store materials during the renovation project whilst causing you minimal disruption? If you do not have enough space, you may need to find temporary accommodation.


Access from Existing Property

How accessible is the basement from your existing property? You will need internal access from your existing home down to the new basement to ensure the basement becomes part of your new home and flows seamlessly into it.

This will most likely be provided through a solid staircase. The stairs from the home to the basement should have an angle of no more than 42 degrees pitch with headroom no less than 2 metres and suitable handrails.



When carrying out a basement conversion, you need to consider your neighbours and what effect the work will have on them. If you live in a terrace or semi-detached property, you will most likely share a party wall with your neighbour. Inform your neighbours of any works you are planning and seek a party wall agreement to ensure your work does not disrupt their property.


Property Structure

What is the structural state of your property and existing walls and foundations? There are a number of elements that can affect and weaken your property’s structure. If the ground is excavated then the foundations will need to be underpinned and the walls strengthened with supporting beams.


House Type

Your house’s potential for a basement conversion could be dependent on your property type. Victorian houses with suspended timber floors can be ideal for basement conversions as work can be carried out from the outside and you can live in the property whilst the renovation takes place.

Some older houses tend to have shallow foundations that can be underpinned first to ensure the property is safe and secure before the basement conversion takes place. On the other hand, modern terraces and townhouses that are built on raft foundations cannot be underpinned, preventing a basement conversion from being carried out.



Geology of the surrounding area can determine whether your property is suitable for a basement conversion. A local building control officer can help you determine what the local ground conditions and soil types are in the area, as can a thorough site investigation or soil survey before construction begins.

Having knowledge of local geology is important as it can inform the design and build of your basement. If the ground around your property is made of stone, clay, or sand, this can cause problems as it can be difficult to install a basement with a solid floor. 



The topography of the land around your property can be used to your advantage when planning your basement conversion. You may be able to exploit different level differences in the land to optimise external accesses, light entry, and ventilation.


Water Table

The water table upon which your property is built will affect the choice of structure and waterproofing of the basement conversion. If you have a higher water table level you won’t be able to dig as deep without the water saturating your basement and it may cause more structural issues, making the conversion more difficult.

A high water table level makes drainage of soil more difficult and you’ll need to keep removing moisture from your basement to keep it dry during the conversion. Your local authorities or water board can inform you of the water table level, as well as the history of flooding in the area. They can advise on the best ways that you can control the water levels and how difficult it will be to progress with your conversion.


Foul Drainage

What are existing provisions for removing foul waste? In a basement, the sewer level will most likely be above ground level so all foul water will need to be collected in a sump and pumped into sewers. If you already have provisions in place for removing foul water, this will make your basement conversion much easier.


Groundwater Drainage & Waterproofing

If your basement is not already waterproofed, you will need to protect your basement from groundwater that is drawn towards your basement as this can lead to flooding and damp. Ensure the gradient of any slopes face away from your house and divert drains to redirect water away from the basement.

Waterproofing your basement will involve resisting groundwater pressure in line with the British Board of Agreement accreditation. Most basements use a cavity membrane which traps damp and channels it down the side of the basement walls and into a sump where it is pumped away. Alternatively, tanking is applied as a render or series of waterproof membranes to create a watertight structure.



Does your basement suffer from damp? If damp is a pre-existing problem in your basement, this will make your conversion more expensive to remove damp and damp-proof the structure. If creating a new basement, it will need damp-proofing to prevent damp and related issues such as rotting wood.



How sufficient is ventilation in the existing basement? Or how easily can you add ventilation in a new basement? Building Regulations state that you need to provide rapid ventilation with an opening which is not less than 1/20th of the floor area and background ventilation of 8000mm² for habitable rooms and 4000mm² for kitchens, bathrooms and utility rooms.



Does your basement get enough light? And will it be easy to add light to your basement conversion? Lighting is essential, but most basements do not receive a lot of light as they are underground.

There are a number of ways you can make sure your basement receives more light, from incorporating more light wells and windows, adding glass doors which open into your garden, to installing a glass rooflight that receives light from above. 



Is your basement high enough? The height of your basement should be at least 2.4 metres. If your ceiling is lower than this you may need to dig a little deeper to create more space, which will make your project more expensive.

When considering the height of your basement, allow for insulation, lighting, ventilation, and plumbing to determine whether you need to excavate further down and whether your property is ideal for a basement conversion. 



If your basement is not already well insulated, you need to take this into consideration when deciding whether your property is suitable for a basement conversion. Insulation should be installed in all external walls and floors all doors and windows should comply with Part L with a U-value of 2.0W/m²K or less.


Fire Escape

If your basement will be converted into a habitable space, an external door or window for escape in case of fire should be installed which can be opened no less than 0.33m² and at least 450mm x 450mm.


Is My Property Suitable For A Basement Conversion?

Before undertaking your basement conversion project, make sure it is a realistic venture for your property.

Whether converting your basement from a cellar or storage room to a more habitable space or excavating the ground beneath your home to create a whole new space, consider building access, neighbours, structure, house type, geology, water table, topography, ventilation, access from the property, foul drainage, groundwater drainage, damp, light, height, insulation, and fire escape to determine whether your property is suitable for a basement conversion.

For more expert advice on basement conversions, get in touch with Allcott Associates today.