House extension and loft conversion specialists in South East London
We are Constructum Code, a full-service London construction company working with private homeowners and commercial clients. We specialise in house extensions, loft conversions, basement conversions, complete property refurbishments, and selected commercial fit-outs. You work with one team — us — from the first concept sketch through to final handover, instead of coordinating separate architects, engineers, and trades yourself.
Bespoke extension and conversion services across London
Structural work in London comes with real hurdles: party wall agreements, planning constraints, and building control sign-off. We take full accountability for the build, so you are not left managing five different companies yourself while the project is underway.
House extensions in South East and Great London
A side-return, rear, or double-storey extension adds real living space without the cost of moving house. We manage the whole process, from concept and structural calculations through to build and handover.
Loft conversions in London
An unused loft can become a bedroom, home office, or master suite. We build dormer, Mansard, and roof light conversions to full fire safety and structural standards.
Basement conversions
When a plot has no room to extend outward, going down adds serious floor space — ideal for properties where side or rear extension is blocked by site boundaries.
Commercial builds
We handle structural fit-outs, office refurbishments, and commercial alterations built around how your business operates, to full commercial building standards.
Regulatory compliance and accreditations
Every structural project in London must satisfy statutory building control standards. We deal directly with local authority planning departments and approved inspectors to secure Building Regulations approval before work starts on site.
We are a verified firm on TrustMark, hold active trade registrations with Certass and FairTrades, and are certified Velux installation partners for roof window systems in loft conversions.
Read more about how we run projects on our company information page, or see how we approach cost control and communication on our project methodology page.
What our clients say
“Fantastic experience with the Constructum team. We had a side return and extension completed in Clapham, and the job was done brilliantly. Communication with Ben throughout the project was regular and clear.”
“I’m very happy with the loft conversion and kitchen extension Constructum Code completed at my house in Bromley. Ben, the manager, kept good communication and came across as a very fair and honest man.”
How we deliver your project
Our workflow runs through four fixed phases:
- Consultation and site assessment — reviewing your vision, budget, and site conditions in person.
- Planning, and engineering — finalising drawings, handling permitted development or full planning applications, and party wall requirements.
- Structural construction — foundations, steelwork, brickwork, roof structures, and weatherproofing.
- Fit-out and handover — insulation, electrical, plumbing, plastering, and joinery, followed by building control sign-off.
For a closer look at how we keep projects on budget and on schedule, see our full project methodology. Common questions about costs, planning permission, and timelines are answered on our FAQ page.
Service area and contact details
Constructum Code Ltd (Company Registration No. 15031868, VAT 454907667) provides construction services throughout Greater London and surrounding regions, including East London, South London, Clapham, Bromley, Lewisham, Southwark, and neighbouring boroughs.
Registered Office: Constructum Code Ltd, Ground Floor Office, Unit 10a Loughton Business Centre, Langston Road, England, IG10 3FL
Direct Phone: +44 7802 756785
Email Enquiries: info@constructumcode.co.uk
Ready to plan your house extension or loft conversion? Contact our team today to request a free quote.
