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CLW
A commercial basement under construction in London where waterproofing risk is managed

Basement Waterproofing Consultant · London

Independent basement waterproofing consultants in London.

On a London commercial basement, a below-ground failure is not a snag - it is remediation, a stalled handover and lost rent, at six and seven figures. An independent waterproofing consultant owns that risk before it becomes a defect.

The problem

London basements concentrate the risk.

London builds deep, on difficult ground, against neighbours. High water tables, made ground, retained-ground walls, party-wall constraints and podium decks over occupied space all arrive at the same interfaces - and it is at those interfaces that below-ground waterproofing fails. The failure rarely shows in the open field of a membrane; it shows at the junctions nobody owned.

When waterproofing is treated as a product to be bought rather than a design to be owned, no single party is accountable for continuity across the structure, the drainage and the finishes. That gap is where most commercial basement defects originate - and on a London scheme, discovering it after pour is the most expensive way to find out. An independent consultant closes the gap by owning the waterproofing strategy end to end.

What we do

We own the waterproofing risk on your scheme.

CLW (legally CSSW.London Limited) is a London-based independent structural waterproofing consultancy for commercial basements. We hold no product affiliations and we do not work for waterproofing contractors, so we can specify what the building needs and write a specification that opens competitive tender. On a typical scheme that means:

  • Below-ground water risk assessment — a structured BS 8102:2022 assessment of the ground, the water regime and the consequence of failure, not a hunch.
  • Grade and system design — the right BS 8102 performance grade and Type A/B/C combination for the building, designed for defect tolerance rather than reliance on one system.
  • Performance specification — a contractual instrument that lets you tender competitively among competent specialist contractors and hold them accountable.
  • Procurement advice — how to compare quotes and tenders on merit, so best value is not confused with lowest price.
  • Construction monitoring — verification on site that what was designed is what gets built, before it is buried.
  • Dispute and expert-witness support — forensic depth when a basement has already failed.

See the full range of CLW services →

Why us

Competent and independent — on the record.

The question on a scheme of consequence is not simply "who is independent" but "who is competent and independent." Against the criteria that matter, here is the plain evidence - and our full buyer's checklist for choosing a waterproofing consultant lets you run the same test on anyone.

Three PCA Waterproofing Design Specialists

CLW employs three registered Waterproofing Design Specialists — Ben Hickman, Adam Leatherdale and Johnny Etkind — the senior PCA credential beyond the CSSW. Design and independent review are carried out by separately qualified specialists, not one person checking their own work.

A contributor to BS 8102:2022

Ben Hickman, CLW's Technical Director, was a contributing member of the BSI committee responsible for the 2022 revision of BS 8102 — the standard the rest of the industry is measured against, and the primary technical reference in UK waterproofing disputes. See the verified credentials →

A chartered, multi-disciplinary team

A basement is structural, architectural, construction-management and engineering risk at once. CLW's chartership spans construction management (MCIOB), building engineering (C.Build E / MCABE) and architecture (ARB / RIBA) — accountability across the disciplines a basement actually engages.

£10m professional indemnity

CLW carries £10m of professional indemnity — sized to the scale of the risk on a commercial basement, not to the fee. We stand behind our design.

A London track record

CLW is appointed by leading commercial developers and project managers to own basement waterproofing risk on substantial London schemes. See selected projects →

CLW credentials, independently verifiable: £10m Professional Indemnity. SSiP Approved Designers. CHAS Elite Accredited. Cyber Essentials Plus. Chartered Building Consultancy (CIOB). PCA member. The Basement Information Centre (TBIC) member.

FAQ

Appointing a basement waterproofing consultant in London

Straight answers on scope, coverage, timing and cost for commercial basement schemes.

What does a basement waterproofing consultant do?
An independent basement waterproofing consultant owns the waterproofing strategy on a scheme: the below-ground water risk assessment, the BS 8102:2022 grade selection, the system specification, the procurement route, and verification of the installation on site. Critically, they hold no product to sell and do not work for the installing contractor, so the design is driven by what the building needs rather than what a supplier wants to sell. What a waterproofing consultant does, in full →
Do you cover the whole of London?
Yes. CLW is a London-based structural waterproofing consultancy and we work on commercial basements across Greater London and the City - from deep basements in the West End and Canary Wharf to podium decks and retained-ground schemes across the boroughs. We also work on major commercial developments nationally, but London basements are the core of our practice.
When should I appoint a waterproofing consultant on a London project?
As early as possible - ideally RIBA Stage 2 to 3, before the structural and drainage strategy is fixed. The waterproofing grade, the Type A/B/C system combination and the drainage all interact with the structure, the ground and the programme, so decisions taken early are far cheaper to get right than defects discovered after pour. Appointing late narrows your options to the expensive ones. When to appoint, and why timing pays →
What does an independent waterproofing consultant cost?
Full-scope independent waterproofing consultancy on a commercial basement typically runs from around £50k to £150k depending on the size and complexity of the scheme, the depth and ground conditions, and the level of construction monitoring required. Set against the cost of a below-ground failure - remediation, stalled handover and lost rent run to six and seven figures - it is a small fraction of the risk it removes. How waterproofing consultancy is priced →
What's the difference between a waterproofing consultant and a waterproofing contractor?
A contractor designs and installs a system they have a commercial interest in selling, and their design liability is narrow - limited to their own product applied to the conditions they were given. An independent consultant has no product to sell and does not work for the installer, so they can select the right strategy, write a performance specification that opens competitive tender, and independently verify the work against the design. On a commercial basement, that independence is what removes the conflict of interest from the advice. Consultant vs contractor, in full →

Have a London basement to protect?

Tell us about the scheme — the ground, the depth, the programme — and we will tell you plainly what owning the waterproofing risk properly looks like. Talk to a specialist directly, or send a project brief.

Discuss your project Call 0207 315 4152