London's structural basement specialists , quietly engineered since 2009.
We deliver basements that stay dry, stay sound and add lasting value to the finest homes in London. Directly-employed teams, written warranties, and a single accountable director on every project from first survey to final sign-off.
Seventeen years under London, thirty years in the trade.
Who we help. Homeowners, architects and family offices across South London and the finest neighbourhoods of the capital, Wandsworth, Clapham, Wimbledon, Putney, Balham, Chelsea, Kensington and Richmond upon Thames. If it sits beneath a London home, we specialise in it.
What we specialise in. Basement excavation, underpinning, conversion, waterproofing and basement extensions. As the market has evolved, our services have expanded beyond basements to include refurbishments, extensions and loft conversions. High-quality finishes and client satisfaction remain central to everything we do.
Experience depth. Underhouse Management Ltd was formed by Ghedeon Costin in 2009. Over the past 17 years, Ghedeon has excavated over 150+ basements and 35+ full refurbishments, along with a wide range of general building projects including extensions. Since 2020, UHM has taken on more above-ground projects and continues to develop its team and skills in this field. Between our two directors there are 30 years of experience in the trade.
Service area. We are London-only, working primarily across South London. Today the business is supported by a dedicated team of 25 directly employed professionals, allowing us to maintain full control over quality, standards and project timelines. Keeping every trade in-house lets us hold consistency across every stage of our work.
Two directors, thirty years between them.
Ghedeon Costin
Formed Underhouse Management Ltd in 2009. Has excavated 150+ basements and completed 35+ full refurbishments, along with extensions and general building projects. Ghedeon attends all sites on a daily basis to brief the team and ensure sites are run safely and efficiently. He holds NVQ Level 6 Site Management and has attended regular training courses to build knowledge and improve the business.
Daniel Purdy
Joined UHM in April 2016 with 15 years of merchant industry experience and extensive knowledge of building materials. Dan completed his NVQ Level 6 Site Management qualification and was made a director in May 2021.
Team qualifications & training
- SSSTS (Site Supervisor Safety Training Scheme)
- SMSTS (Site Management Safety Training Scheme)
- Asbestos Awareness
- Confined Space Training
- First Aid
- Temporary Works Co-ordinator
- Face Fit Training
Accreditations & memberships
- FMB (Federation of Master Builders) accredited member
- Delta Registered Waterproofing Installers
- Considerate Constructors Scheme member
Underhouse Management Ltd, company number 06968521.
Four standards that don't bend on any site.
Our philosophy is simple: fewer projects, delivered by the same directly-employed team, to a written specification, with insurance and warranties backed by paperwork you can read before you sign.
Designed to BS 8102:2022
Every waterproofing scheme meets the current British Standard. Combined Type A / B / C systems specified where risk demands, not the cheapest single option.
Structural work by our own team
Excavation, underpinning and waterproofing are delivered exclusively by our directly-employed team. One accountable party from first survey to final sign-off.
Independently monitored sites
Every UHM project is registered with the Considerate Constructors Scheme, giving neighbours a direct, independent channel for the duration of the works.
Written 25-year warranty
A 25-year structural warranty and 25-year Delta-backed waterproofing warranty are written into your contract before ground is broken, never sold as an add-on.
The numbers behind every project.
Accreditations, chronologically.
Nine years of independently monitored site ratings and manufacturer accreditations. Slide through each certificate, every one has been verified by an external body, not self-awarded.
4-Star Rated Site Award
Considerate Constructors Scheme · 2021
Our most recent Considerate Constructors rating, awarded after independent monitoring against the Code of Considerate Practice. Every UHM site is registered with the Scheme so residents have an independent channel to raise any concern.
- Independently monitored 2021
- Every UHM site registered with CCS
- Independent resident feedback channel
Ready for a free structural survey?
Book a no-obligation site visit with one of our directors. We'll walk your property, discuss the brief, and give you a written feasibility summary, free.
- Free site visit
- Free written quote
- 25-year warranty
- £10M insurance
- Directly-employed team