Many of the grand stucco-fronted houses of Kensington, Chelsea and Notting Hill were built with a lower ground floor, front lightwell and vaults under the pavement. Today these spaces are often flats or extra living space, and they are some of the most damp-prone rooms in London.
Below ground, against the soil
Lower ground floor walls have earth against them on at least one side. Moisture in the ground presses against the walls and floor, and London Clay holds that moisture rather than letting it drain away. Original walls were never designed to keep it out completely.
Vaults and lightwells
- Pavement vaults are often damp, with water getting in through the pavement above, coal holes and failed asphalt
- Lightwells collect rainwater, and blocked gullies can flood against walls and doors
- External steps, planters and raised areas bridge walls and trap moisture
Why old tanking fails
Many lower ground floors were “tanked” years ago with renders or coatings that have since cracked or been damaged by later work. Water then gets behind them and damp reappears, often with salts.
A designed waterproofing system
Below-ground rooms are best protected by a system designed for the space and the ground conditions, often a cavity drain membrane with drainage and a sump pump, sometimes combined with tanking. Vaults can be waterproofed the same way and turned into useful storage or living space.
Leaseholders and freeholders
In converted buildings, responsibility for walls, vaults and lightwells may sit with the freeholder or be shared. A clear survey report helps everyone agree the cause and the fix.
We have waterproofed basements across Kensington, Knightsbridge, Marylebone and Notting Hill. Read more about basement waterproofing in London.
