If you have been following our market insights and podcasts and are familiar with Prime Central London, then you will know that there is generally very limited property stock available for purchase. Of the limited property stock available, space comes at a prime cost, particularly in Prime Central London areas. 

While many consider building upwards to maximise on space, this has its downsides and limitations. Planning applications and permission are very difficult to obtain, not to mention objections from neighbours about obscuring views and the many listed buildings in London which you are not permitted to alter.

These restrictions have contributed to a quiet surge in residential basement constructions over the last two decades.

A recent study published in mid 2021 has mapped out “in detail the emerging subterranean geography of residential basement development across London since 2008”. This study, undertaken by Roger Burrows of Newcastle University, showcases that the super wealthy have in fact been taking advantage of this opportunity in certain parts of London and that by doing so they have capitalised not only on space but also on adding further value to already elite and expensive housing. 

According to the study, basement extensions are relatively affordable when compared to the cost and difficulty of building up or moving to a bigger property in the same neighbourhood. This factor has contributed to the speculative value of the properties with underground extensions. In 2015, according to their research, it was claimed that for every 1000 USD invested in a basement extension the overall value of the property could be increased by about 2000 USD. A very attractive margin indeed!

As you can imagine, these basement extensions come not only at a monetary cost but can cause neighbourly relations to break down. A renovation of any kind is very stressful.  Excavation, the time it takes and the impact on the neighbourhood in terms of noise and disruption have to be taken into account. 

Many celebrities and high profile individuals have complained vocally in the media about the impact of these extensions and in some cases claimed that the basement extensions have led to structural damage of their bordering properties.

Concerns about the impact of these extensions is not only limited to undermining or destabilising the property itself and any neighbouring properties. The impact on deep rooted flora, the increase of flood risk if the underground water source is not managed properly and alterations to ground acoustics and noise implications are all concerns being raised by politicians. 

Either way, with the limited space above ground throughout London as a whole and the shortage of stock, perhaps underground extensions are the way forward in the future.