Vault Waterproofing
Dry, usable vaults under the pavement, protected for the long term!
Most vaults in London sit directly beneath the pavement, right next to the street. That means they are constantly exposed to rainwater soaking through from above, vibration from passing pedestrians and traffic, and road salt in winter. Over time this leads to structural cracks, water leaks and mould. At Crystal Damp Proofing & Basements Ltd, we specialise in under-pavement vault waterproofing, turning damp, unusable vaults into dry storage, utility rooms or living space.
Why Are Under-Pavement Vaults So Vulnerable?
- Water from above and around: rain soaks through the pavement and surrounding ground straight into the vault walls and ceiling.
- Vibration from traffic: constant movement from vehicles and footfall can crack rigid coatings over time.
- Road salt: in winter, salty water reaches the masonry and speeds up its deterioration.
- Poor ventilation: damp, enclosed spaces quickly develop mould and a musty smell that spreads into the rest of the property.
The System We Recommend: Cavity Drain Mesh Membrane (Type C)
For under-pavement vaults, we recommend a cavity drain membrane system, known as Type C waterproofing under BS 8102:2022. Instead of trying to block the water completely, it safely controls and removes it. Because the membrane is flexible and not rigidly bonded to the structure, it copes well with vibration from the street above, which makes it a much safer choice for vaults than rigid cement coatings.
How it works:
- Survey and preparation: we assess the vault, clean the surfaces, treat any mould and repair damaged areas.
- Membrane installation: a studded waterproof membrane is fixed to the walls and vaulted ceiling, creating an air gap behind it.
- Perimeter drainage: any water that comes through runs down behind the membrane into drainage channels set into the floor.
- Sump pump: the channels carry the water to a sump with an automatic pump, which discharges it safely outside the building.
- Finishing: once the vault is dry and protected, it can be finished to suit your plans, from simple storage to a fully finished room.
Why Waterproof Your Vault?
- Protects the structure: stops water weakening the masonry, causing cracks and corroding steelwork.
- Healthier home: no more mould spores spreading through the air you breathe.
- No more musty smell: a dry vault means fresh air throughout the property.
- Lower heating costs: dry air is easier and cheaper to heat than damp air.
Added Value When Selling Your Property
Buyers rarely want extra problems and costs, so a dry, protected vault is a strong selling point:
- More usable space: instead of a damp storage area, buyers see a home office, gym, utility room or extra living space.
- A cleaner survey report: signs of damp or flooding are one of the most common reasons buyers pull out or ask for a big price reduction.
- Stand out from the competition: a property with a dry vault, backed by a guarantee, sells faster than a similar one without.
- A guarantee that transfers to the new owner: our 10-year Insurance Backed Guarantee passes to the buyer if the property is sold, giving them extra confidence and giving you a strong negotiating point.
Listed Buildings & Conservation Areas
Many vaults in London belong to listed or period buildings. If your property is listed, you will need Listed Building Consent from your local council’s planning department before any work starts. Your case will be handled by a Conservation Officer, who checks that the work will not harm the historic fabric of the building. Carrying out work on a listed building without consent is a criminal offence.
Where the pavement and outer structure cannot be altered, internal waterproofing is usually the only effective option, and conservation officers generally favour Type C membrane systems because they protect the vault without damaging the original masonry. Our CSSW-qualified surveyors have experience with period properties across Notting Hill, Marylebone, Soho and Kensington. We help you with the whole process: together with our architects and engineers, we prepare the architect drawings and technical details and help you submit your Listed Building Consent application.
Trusted Manufacturers & High-Quality Materials
We use proven products from well-known manufacturers such as Newton, Wykamol, Delta, Biokil and Mapei. Together, they form one complete system that keeps your vault dry for years to come.
Qualified Specialists & a 10-Year Guarantee
Our family-run team holds CSSW qualifications, with a minimum of 10 years’ experience each. We back our work with a 10-year guarantee covering workmanship, plus a QANW Insurance Backed Guarantee that transfers to the new owner if you sell your property. Based in Croydon, we work on domestic and commercial properties across London and the South East.
See What Our Clients Say
We are proud of our 5-star Google rating: see our reviews. If your basement is damp or takes in water, book a survey in our Booking Survey section, or call or message our fully qualified advisors.
