London’s Leading Basement Conversion Specialist


Thinking of carrying out a basement conversion to your property in London? Here is a list of our most commonly asked questions.

If you still can’t find what you are looking for, why not call us on free phone 0800 917 7571 and ask for a call back from one of our technical team members.

What can I use my basement conversion for?

You can use your basement conversion for anything you want to within reason. Some popular ideas are a home gym, swimming pool, cinema room, kitchen, wine cellar, yoga studio or kids’ playroom. Whatever you want to use your basement conversion for, the Simply Basement team will be able to advise you on what you need to make it happen – or you can take a look at our basement conversion ideas page.

How long does a basement conversion take?

The duration of a basement conversion can vary dramatically depending on the size and scope of the work. This will also depend on whether you require Simply Basement to carry out only the dig out, structural and waterproofing stages or whether you would like us to complete the entire conversion including fit out and decoration. On average it can take anywhere from a couple of months through to a year for more complex projects. When a Simply Basement surveyor has visited your site and understands the scope of work you would like to do, we will then advise you on the most accurate timescales for your project.

How much does the average basement conversion cost?

As a guide, a London basement conversion can cost anywhere upwards of £180k. Ultimately, the cost will depend upon the size of the conversion and the fixtures and fittings you require. After your free site survey, Simply Basement will be able to provide you with a full, comprehensive quotation for your build to give you a much clearer idea.

How long are your quotations valid for?

A quote from Simply Basement is valid for six months from its date of issue.

Do I need to have an existing cellar or small basement to be able to carry out the work?

You may be surprised to find out that you do not need to have an existing cellar or basement space to be able to create your basement conversion! Here at Simply Basement we are able to work on most types of property and can advise you as to what’s possible for your home.

How much head height can I have in my basement conversion?

On average most basement conversions opt for a minimum 2.6m head height for it to feel spacious enough. Our clients of course can opt to go higher if needs be, although this will affect the price and sometimes duration of the project.

Will I need planning permission for my basement conversion?

Yes this will most certainly be a requirement if you are looking to make the space into a habitable room. Exceptions to planning are usually when you convert an existing residential basement and the outside is visibly unaltered. Planning usually takes 8 weeks to obtain, possibly longer if revisions are required. Our Simply Basement team of architects are on hand if you require them to help you come up with plans and submitting through to planning. Find out more information on basement conversion planning permission in London.

Can my basement conversion be on more than one level?

In some cases yes, however this will depend on what you can obtain through planning permission. In some boroughs of London only one level of basement is obtainable. If you want to explore options, we have a dedicated design and architectural team who are able to work with you to come up with a design that will be able to be submitted through planning.

What is a design and build process and how will it work on my basement?

The design and build process is, simply put, the procedure we follow to plan, build and complete your basement conversion in London. It takes into account the following steps or stages:

  1. Site survey and quotation
  2. Contract and deposit
  3. Design and planning with an architect
  4. Party Wall Agreement
  5. The build
  6. Completion and sign off

You can find a fuller description of how the design and build process for basement conversions is applied to your project here.

Do I need to move out during construction of the basement?

In most cases, our clients are able to live at their property whilst the conversion is taking place. Some clients prefer to rent on a short term basis whilst the heavy work is being carried out. The choice is entirely yours.

Will I need a party wall agreement?

Normally a party wall agreement is required for basement conversions. Each neighbour will have to be informed of the proposed works using a party wall notice form at least two calendar months before the intended start of the build. The party wall agreement is there to protect you and your neighbour from issues that might arise due to work done on the party wall. It draws up an agreement between you and your neighbour on what needs to happen if there is a problem. By law your neighbour can insist you have one before the work starts. If you require assistance in this process Simply Basement can put you in contact with one of our certified party wall surveyors.

What areas of London do you cover?

We work in most areas of London, if you are unsure please call our bookings team on 0800 917 7571.

Do you carry out basement conversion work for developers?

Yes. In fact, we are currently working with developers on numerous projects across London.

Can I have other refurbishment work done at the same time as my basement conversion?

Simply Basement forms part of the Simply Construction Group which owns both Simply Loft (loft conversions) and Simply Extend (extensions and refurbishment), therefore we are perfectly positioned to be able to quote for other parts of construction and refurbishment work to your property.

What guarantees and warranties do you have in place for my basement conversion?

Simply Basement offers the following guarantees for your peace of mind:

  • Company backed structural guarantee of 10 years
  • Insurance backed guarantee of 10 years on waterproofing
  • 30 year manufacturer guarantee on Delta Membrane waterproofing systems.
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Call us today on 0800 917 7571 Or fill out an online enquiry form.

Next step is our friendly and helpful advisors to take details of your proposed project and arrange a free, no obligation site survey of your home.