According to a 2016 Zoopla survey, how much your basement will cost depends on where you live – in Dagenham East a basement conversion will cost £302 per square foot, rising to £2,214 per square foot in Knightsbridge. But offset that against the cost of moving, with stamp duty on the average London property starting at £30,000, and a basement conversion starts to look like very good value indeed.

What If My Property Is Leasehold?

Your property may still be suitable for a basement conversion even if you’re not a freeholder, but obviously the process will become a little more complicated. For example, if you own a leasehold ground-floor flat, you may be able to convert the basement if you get agreement from the freeholder and the other tenants in your building. Your party-wall agreement will have to cover all the other flat owners in the building plus the homeowners on either side.

Leasehold agreements can involve complications, so you’ll need to have a solicitor take a look at it. However, it will give you a very clear and accurate picture of what land and subsoil are legally granted to your leasehold.

Converting the Basement in a Period Property

We no longer have sculleries for the maid or coal cellars for our heating, leaving period homes with often a warren of basement rooms that are ripe for conversion. You won’t need planning permission if you choose to convert this space, as it comes under the permitted development guidelines unless you live in a listed property or in a conservation area – in which case you’ll need to contact your local council planning department.

You’ll also need to be aware that should you want to excavate the floor to give additional head height, you may need to apply for planning permission. Again, it’s best to check with your local planning office before you make any decisions. If you intend to extend the existing basement under your garden or driveway, or your basement will be undergoing a change of use, you will be subject to building regulations.

If you’re thinking of a basement conversion in a period property, then it would be better to make a Full Plans Application for your planned development rather than simply following the Building Notice procedure.

Planning for Success

Whether you have a Victorian villa, Georgian town house or a ’60s pad, your London property will be suitable for basement conversion if you follow the planning procedures to the letter and use the services of an experienced basement construction specialist who knows how to add value and balance the ratio of cost to value so you maximise your return on investment.

You may see a basement conversion as the answer to all your space worries and as a sound investment for the future, but consult the professionals first and make sure your planning is watertight before you start work.