Recent press photographs showing buildings literally being ripped at the seams, may well put off prospective clients and developers from seeking to install basements under their properties.

But basements can be an excellent way to maximise space within a property. So what do you need to know in order to build an effective basement?

We’ve highlighted 8 pitfalls and things to look out for when constructing a basement so that this doesn't happen to your basement conversion.

Basements - House of horrors or a fairytale ending?

1. Planning

In central London Boroughs such as Kensington and Chelsea, basements are pretty much restricted to only one storey down and up to 50% of the rear garden. So called iceberg basements are now a thing of the past following a reform on the planning process by the Planning Inspectorate earlier this year.  Although this may seem like a major blow there is still a real opportunity to build basements on a one storey level. This has always been the case for the majority of the domestic market which is still thriving.


2. Check Planning requirements

Planning requirements may vary by borough, so make sure you check their planning requirements, as many request a Basement Impact Assessment and a Construction Traffic Management Plan be submitted with applications.


3. Choose a competent contractor

Choose your contractor carefully for example by selecting an ASUC member to ensure they have the relevant experience to carry out such works commensurate with the size of the project.

Competent contractors will have insurances in place appropriate to the type of work and will also provide a 10 year Basement Insurance Guarantee. This is called latent defects insurance and is a first party policy not dependant on the contractor trading in order to make a claim.


4. Health and Safety

A recent HSE blitz revealed in excess of 50% of sites visited were not conforming to health and safety requirements. ASUC’s member figures were considerably reduced from this figure with minor infringements only noted.


5. Price

There is a tendency to go for the cheapest quote for works, but this is not necessarily a good thing, as cheap often means shortcuts. With the potential problems associated with basements it pays to employ a credible specialist.


6. Engage with an Engineer

Choose an engineer who understands the issues involved with permanent and temporary design and has appropriate Professional Indemnity Insurance in place to cover their works.


7. Party Wall award agreements

You will also need to acquire a Party Wall agreement if the works are within 3m of your neighbour’s property. As would be the case in almost all instances in Central London.


8. ASUC members

ASUC members can provide both an installation and design and build service providing peace of mind for a client to have a fairy tale ending and not the House of horrors often featured in the press.

For more information on ASUC and its members please visit

Rob Withers
Executive Director at ASUC

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Please Note: Every care was taken to ensure the information in this article was correct at the time of publication. Any written guidance provided does not replace the reader’s professional judgement and any construction project should comply with the relevant Building Regulations or applicable technical standards. However, for the most up to date LABC Warranty technical guidance please refer to your Risk Management Surveyor and the latest version of the LABC Warranty Technical Manual.

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