Welcome to SubStructural, a leading provider of expert basement design solutions in London and beyond. Whether you’re building a new development or expanding beneath an existing structure, our team of highly experienced engineers, with over 25 years of experience, is equipped to offer innovative and effective design solutions, whatever the situation.

At SubStructural, we employ the latest technological advancements in design software to support our engineers in delivering optimal design solutions. Our commitment to efficiency and cost-effectiveness ensures that we provide practical alternatives to conventional design and construction processes, resulting in both time and cost savings on your project.

In response to the increasing demand for space, particularly in and around London, utilising the ground space below a property is an excellent way to maximise its footprint. Basement designs offer a practical and valuable alternative to relocating, significantly enhancing both the habitable space and the value of your property.

We have a proven track record of designing luxury basements, including notable projects like the expansive basement extension at the Shaftesbury Theatre. From period townhouses and public houses to modern executive homes, our basement solutions are bright, spacious, and functional.

If you’re interested in exploring the potential of your property, contact SubStructural today for an informative, no-obligation conversation with one of our basement design specialists.

What We Do

Basement Impact Assessments (BIAs)

We can prepare subterranean reports that meet and satisfy Local Authority planning requirements. A Basement Impact Assessment gives due consideration of the effects of a new basement on ground water, flooding, and any existing surrounding buildings. We can also arrange site investigations, flood risk assessments and drainage surveys.


We utilise advanced modelling software to create sophisticated designs. To assist you in comparing costs, we can seamlessly evaluate options such as mass or reinforced concrete walls versus cavity reinforced masonry solutions. Additionally, we have expertise in piling techniques, underpinning, and “top down” construction, as well as materials like Stepoc Blockwork and Insulated Formwork (ICF).


We are experts in all forms of underpinning including double depth underpinning – i.e. for swimming pools – to maximise usable space. Whilst underpinning is traditionally used for construction beneath existing buildings, it can also be used for two stage new build foundation construction. This technique has proved useful for sites with poor ground and limited access, where piling or similar cannot be used.


If ground conditions are favourable and space on site allows, reduced dig techniques can sometimes be employed to enable reinforced concrete retaining walls to be constructed. This can be very cost effective as additional costs for either piling or an extensive temporary works scheme can be reduced.


Staircase installation for basement design in N.London
New build basement set below a new residential apartment block
Cantilevered piled solution with suspended basement floor
Mikvah designed for London client


Whether it be a large commercial project or a domestic home extension, JMS has over 25 years experience of designing basements for all applications nationwide and particularly in the London area.

As well as being able to provide robust, cost-effective design solutions, Substructural can assist from the beginning of a project, producing Basement Impact Assessments (BIA’s) to help obtain planning consent and get construction started.

The criteria set out by the planning authorities for BIA’s is often extensive and will involve a detailed examination of the ground conditions, groundwater, potential ground movement, and the impact on the surrounding area.

JMS have the knowledge and experience to address those requirements within a detailed report, ensuring that basement proposals are viable and constructed safely.