Wandsworth Tightens Regulations on Basement Builds

Across London, basement extensions and conversions are facing increasing scrutiny. Back in December, I wrote about the limits the Royal Borough of Kensington and Chelsea had placed on basements of two or more storeys below ground, banning 120 applications in the process. Westminster since tightened their regulations and now Wandsworth has followed suit.

My opinion on basements is unchanged. In December, I wrote, “basements provide an uninstrusive and convenient increase of floorspace and value, while – thanks to advances in technology and design – being just as comfortable as the floors above them. Dense urban areas with few options for above ground expansion don’t just benefit from them, they need them.”

I have full confidence in the ability of myself and my practice – with the assistance of qualified surveyors and consultants – to design and build basements that provide only a positive impact to the surrounding area, the property itself and the lives of those who inhabit it.

Wandsworth Council has taken a more cautious approach. Their recent update to the Supplementary Planning Documents (SPD) for basement developments is a mix of some sensible regulatory requirements along with disappointing resistance towards more ambitious builds.

For multi-level basement extensions in particular, Wandsworth seem to be following the precedent set by RBKC:

“Unlike traditional extensions which have minimal impact on ground conditions, basement extensions, particularly when greater than one storey in depth, can permanently and irreversibly alter ground conditions. They are permanent fixtures, likely to exist throughout the lifetime of the building and beyond, which will result in a loss of infiltration and planting ability of a garden permanently and cumulatively. Taking this into account and given that significant areas of the borough are at risk from flooding, multi-level basements are not considered appropriate in Wandsworth.”

It’s a disheartening statement though I wonder if and how exceptions can be granted. At DGA, our pursuit of the utmost quality and ability to tirelessly argue our case has allowed us to see builds to completion that usually wouldn’t get past the desks of the planning department. Multi-level basements may be harder to have approved in Wandsworth but time will tell if it’s truly impossible.

There are also restrictions on how far the basement can extend beneath the front and back gardens, with particular attention (as expected) to how they may alter the street facing appearance of the house – though their recommendation for lightwells to be covered by a grille doesn’t seem the most elegant.

Beyond project specific concerns, the key change that impacts all basement developments is that Wandsworth now recommends all applications be supported by a Construction Method Statement at the applicant’s expense. These are documents detailing how the build will be carried out safely and compliantly with evidence from accredited surveyors, assessors and consultants – in this case, that includes expensive borehole testing.

Much of the CMS requirements are good practice procedures that we would normally address during our projects, though only after planning permission has been secured. Wandsworth recommending that planning applications be accompanied by a CMS drives up their cost significantly. Luckily, our high approval rating and expertise in compiling both CMS and planning applications means that, despite being more expensive, the process doesn’t need to be more risky.

Currently the basements SPD states that a CMS is only required for listed buildings but – in my experience – even if a policy is only “encouraged”, one may as well consider it mandatory to face a fair chance at gaining approval, especially in sought after areas such as Wandsworth.

There are also a number of quality and safety considerations the SPD requires developers to take into account that are entirely fair, such as ensuring there’s no damage to subterranean infrastructure, protected trees and the stability of the property or neighbouring properties. And of course, all basement developments must abide by building regulations for habitability, safety and sustainability.

I recommend reading the entire SPD if you’re considering a basement extension in Wandsworth, and the document also provides advice for neighbours. It should give you a good idea of what is and is not possible, and we’re always available if you need further guidance on how to make your home bigger, better and more valuable.

By John Dyer-Grimes