Before you jump into a basement conversion project, it’s important to consider all the cost implications to ensure that you can afford the necessary work and have it finished to the right standards. There are a number of basement contractors in London who can help you to put a design plan together that meets your preferences and budget requirements.

Here are some of the elements that will have an effect on the final quote.

Do you have an existing cellar?

A typical London basement conversion cost could be reduced if there is already an existing cellar or useable space under the property and no structural work is required. However, the costs will start increasing substantially if it’s necessary to lower the floors or increase the head height in order to accommodate the room, so speak to your contractor about how suitable the space is.


If you need to excavate a new basement, there will be considerably more work involved and this will have an impact on the cost. You will need to factor in the cost of taking away the excess materials, as well as damp proofing or tanking the room, re-routing drains or sewers, underpinning the walls and any topography issues, like a high water table or difficult ground conditions. Other issues that can put up the price of a conversion are the type of subfloors, as solid concrete ones will be harder to remove than timber. Access to the site for contractors can affect the type of equipment they can use and how easy it is to carry out the work.

What you’ll use the basement for

Another area that will be a factor when working out the cost of a basement conversion is how you are going to use the room. Some common uses that will be cheaper to implement include home gyms, play rooms and media rooms. However, if you’re considering fitting a new kitchen, or even a swimming pool, these will be more complicated and so increase the cost.

Whatever the end use for your conversion is, take care to research the contractor you intend to employ thoroughly and look at London basement company liquidation records to ensure that they are a professional and financially solvent source.

Extra costs

As well as the standard conversion costs, there are additional factors that can increase the price, such as planning applications, building regulations, party wall agreements, engineers fees, whether an exterior access point is required and if the contractor or any consultants are VAT registered. These can often be forgotten about by homeowners, who then end up paying more than they anticipated, which could result in the conversion not being completed or finished to a lower standard.

It’s essential that you speak to a specialist company first if you’re considering a basement conversion, and they will be able to run through all the options with you to find a solution that’s within your budget.