07450 310772sales@uhmbasements.co.uk FMB  ·  Delta Registered  ·  £10M Insured  ·  25-Year Warranty About Services Areas Our Work Reviews Contact 07450 310772Book a site visit Damp Proofing · London # Basement damp proofing in London,diagnosed properly,solved permanently. A proper damp diagnosis before a single product is specified, followed by a Delta-registered cavity drainage or barrier system that carries a 25-year waterproofing warranty. No paint-and-hope surveys. Book a free site visit 07450 310772 Delta Registered Installers · 25-year waterproofing warranty · Free damp survey and written report. Delta Registered Installers 25 yr Waterproofing warranty BS 8102 Design standard £10M Insurance cover FMB Accredited members Recent work ## Recent projects, delivered by UHM. View the full portfolio → Service overview ## Damp is a symptom. The point of a good survey is to find the cause. Damp in a London basement is rarely one thing. It's usually a combination: rising damp from the ground, penetrating damp through the walls, condensation from poor ventilation, or a failed previous waterproofing job. Treating the symptom without diagnosing the cause guarantees the problem returns. We survey first, then specify. What it is A structured survey of damp presentation, moisture readings and ventilation performance, followed by a specified remedial system: cavity drainage, barrier tanking, ventilation upgrade or a combination, designed to BS 8102 and installed by Delta Registered Installers. Who it's for Homeowners with an existing basement or cellar showing damp signs, buyers or sellers where the surveyor has flagged damp evidence, and property owners whose previous waterproofing has failed. When it's needed At the first sign of damp: musty smell, tide marks, salts on plaster, mould in corners, cold spots on walls, or a surveyor's report flagging damp. Why it matters Damp untreated damages every finish it touches, affects air quality and blocks sale. Damp treated with the wrong system fails again within months. Only proper diagnosis and specification gives a permanent solution. Our process ## Structured stages, no shortcuts. Every UHM project runs through the same structured stages. You'll always know what's happening next, who's doing it and when it completes. - 01 ### Damp survey & diagnosis A director surveys the basement, takes moisture readings, checks ventilation and identifies the source or sources of damp. - 02 ### Written diagnosis & specification A written report with the diagnosis, recommended system and specification to BS 8102, before you commit to any works. - 03 ### System installation Delta cavity drainage, Type A tanking, ventilation upgrade or hybrid installed by our directly-employed, Delta-trained crew. - 04 ### Ventilation & commissioning MVHR or extract designed and commissioned. Sump-and-pump tested with alarm and back-up. Documented results. - 05 ### Warranty & maintenance plan 25-year waterproofing warranty, commissioning report and annual maintenance schedule handed over. Technical detail ## The damp types we diagnose, and the systems that solve them. Basement damp comes in recognisable types. Each has a proven remedial approach. Here's the toolkit we work with. ### Rising damp Moisture drawn up from the ground through masonry by capillary action. Presents as tide marks on lower walls and salt deposits on plaster. Solved by cavity drainage or, on select walls, chemical damp-proof course installation combined with breathable finishes. - Moisture readings taken at multiple heights - Chemical DPC injection where appropriate - Cavity drainage as long-term solution - Breathable lime plasters where specified ### Penetrating damp Moisture pushing through walls from ground contact or defective external detailing. Presents as patch damp on lower walls, sometimes with visible efflorescence. Solved with Delta cavity drainage (Type C), external drainage improvements or Type A barrier tanking depending on the situation. - External ground level and drainage review - Delta MS 20 cavity drainage installation - Cementitious tanking where structure allows - Perimeter channels to sump-and-pump ### Condensation damp Warm, humid air meeting cold surfaces below dew point. Presents as mould in corners, on wardrobe walls and behind furniture. Solved with mechanical ventilation (MVHR), insulation upgrades and, where necessary, humidity-controlled extract. - MVHR system design and installation - Humidity-controlled extract to bathrooms and utilities - Thermal upgrade of cold-spot walls - Air change rates sized to habitable room use ### Failed previous waterproofing A previous cavity-drainage or tanking system that has failed. We survey the existing installation, identify the failure mode (pump failure, drainage blockage, membrane damage, wrong system for the risk class) and specify remedy, often extending or replacing the existing system rather than starting over. Why it's worth doing properly ## Concrete outcomes, not vague claims. ### Diagnosis before product We won't quote you a system before we've surveyed the source. Anyone who does is selling, not solving. ### 25-year waterproofing warranty As Delta Registered Installers, our finished damp-proofing work carries a documented 25-year warranty. ### In-house Delta-trained crew The same directly-employed team installs everything from the sump to the plastering, no handover gaps. ### Fast survey response Most damp surveys booked within a few working days. Reports usually delivered inside a week of the visit. ### Documentation for surveyors Written diagnosis, specification, commissioning report and warranty certificate, exactly what buyers' surveyors and lenders ask for. ### Rooms that feel different A properly de-damped basement doesn't just look right: it smells right, sounds right and lives right. The real cost of the wrong contractor ## Every year you leave damp, the fix gets more expensive. Damp doesn't stabilise. It progresses through finishes, joinery, floors and eventually structure. What was a £2,000 remedial job becomes a £20,000 strip-out. And the impact on how the room feels is immediate. ### Progressive damage to finishes Skirtings rot. Plaster salts. Floor coverings lift. Wardrobes bow. Every finish above the damp line becomes disposable, and every strip-out costs more than the original fix. ### Health impact of chronic humidity Sustained damp creates airborne mould spores. It affects sleep, respiratory health and the way children use lower-floor rooms. ### Blocked sale, forced renegotiation Buyer's surveyors flag basement damp aggressively. A missing waterproofing warranty triggers retention on the sale price, or worse, the buyer walks. ### Common homeowner mistakes. - 01Painting damp-proof paint over damp brick, the industry's most-sold placebo. - 02Injecting a damp-proof course as a universal answer to every damp problem. - 03Ignoring ventilation and treating only the walls. - 04Accepting a diagnosis from someone selling a specific product. - 05Installing cavity drainage without a maintained sump-and-pump. - 06Skipping the commissioning report, no report means no meaningful warranty. Frequently asked ## Real answers, before you call. Straight answers we give on almost every free site visit, cost, timeline, guarantees and what's included. 07450 310772Message us ### How much does damp proofing cost in London? Priced per project. The number depends on the cause and scale of the damp, the system specified and the state of existing finishes. Site visits and written specifications are always free. ### How long does a damp proofing job take? A cellar-scale cavity drainage installation typically completes in three to six weeks. Isolated damp remediation is shorter; full-basement systems take longer. Programme is confirmed in the written quote. ### Is damp proofing paint enough? Almost never. Paints and coatings applied to damp masonry trap moisture and delay the symptom rather than solve it. We won't specify a paint job when a system is needed. ### How do I know which damp type I have? That's what the survey is for. Rising, penetrating and condensation damp look similar to the untrained eye but need different solutions. A proper diagnosis prevents you paying twice. ### Do damp treatments come with a warranty? Yes. Delta-registered installations carry a 25-year waterproofing warranty. Chemical DPCs and specific product treatments carry manufacturer-backed guarantees, all documented at handover. ### Will the treatment involve stripping finishes? Usually, in the areas being treated. Cavity drainage requires access to the wall face, and plastering is done fresh over the new membrane. We sequence works to minimise disruption elsewhere in the home. ### Do I need mechanical ventilation as well? Almost always, if the basement is habitable. Mechanical ventilation with heat recovery (MVHR) manages humidity properly. We specify it alongside the damp system, not as an afterthought. ### Are you insured? Yes, £10M all-risks insurance covering public and employers' liability. Documentation available on request. Related services ### Explore the full basement discipline - Basement Waterproofing - Sump & Pump Systems - Cellar Conversion - Basement Conversion - Basement Excavation - View all services Where we work ### Serving South London first - London - Wandsworth - Clapham - Wimbledon - Putney - Balham - Chelsea - Kensington Book your free site visit ## Ready to diagnose the damp, and solve it once? Book a proper survey. A director will survey your basement, take moisture readings and give you a written diagnosis and quote, for free. If the answer is 'do nothing yet', we'll say so. - Free site visit - Free written quote - 25-year warranty - £10M insurance - Directly-employed teamRequest your free quote 07450 310772 Or return to the homepage · read about UHM. Underhouse Management Ltd, London's structural basement specialists. A directly-employed team of 25, delivering meticulous below-ground work across the capital's finest addresses. Established 2009. FMB·Delta Registered·Considerate Constructors ### Services - Basement Excavation - Basement Conversion - Waterproofing & Tanking - Underpinning - Cellar Conversion - Basement Extension ### Areas Served - London - Wandsworth - Clapham - Wimbledon - Putney - Balham - Chelsea - Kensington - Richmond upon Thames ### Contact - 07450 310772 - sales@uhmbasements.co.uk - Unit C220A, Trident Business Centre,89 Bickersteth Rd, London SW17 9SHBook a site visit © 2026 Underhouse Management Ltd (t/a UHM Basements). Company No. 06968521. Privacy Policy·Terms & Conditions·Cookie Policy·25-year warranty · £10M insurance Call nowBook a site visit