Turning a Lower Ground Floor Vault Into a Dry Pantry in Canonbury, N1
A vault at lower ground floor level in a Canonbury period house had no waterproofing at all. The owners wanted to use it as a dry pantry, so our surveyor designed a Type C cavity drain system with a dual pump sump.
Project at a Glance
The Brief
The owners wanted to turn an unused vault off the lower ground floor into a pantry. Vaults like this sit directly against the surrounding ground and were never built to stay dry.
The Survey
Our surveyor assessed the vault and found there was no physical barrier of any kind to manage ground water: no cavity drain membrane (Type C) and no internal or external tanking (Type A). For a room used to store food, the space needed to be reliably dry all year, so the recommendation was a full waterproofing system rather than a coating.
The Solution
We specified a Type C cavity drainage system designed to BS 8102:2022.
- Lift the existing floor tiles in the vault.
- Fix a studded HDPE cavity drain membrane to the walls and floor, so any water coming through the structure is collected behind the membrane instead of reaching the room.
- Link the membrane to a perimeter drainage channel running to a dual pump sump set below floor level, so a second pump takes over if the first fails.
- Line the walls with studded plasterboard and finish with a skim coat, ready for decoration.
The final floor finish was left to the owners’ own contractor, as agreed in the specification.
The Work
Pipework and electrics were worked around as the lining went on, keeping the services accessible behind the new walls.
The Result
The vault is now a drained, lined space ready to be fitted out as a pantry. The membrane itself needs no maintenance, but the sump pumps should be serviced regularly to keep the system working as designed. Many Islington houses have similar vaults under the garden or pavement. See our page on basement waterproofing in Islington.
Frequently Asked Questions
Can a vault under the garden or pavement be made dry?
Yes. A cavity drain membrane with drainage and a sump pump manages the water that comes through the walls and floor, rather than trying to hold it back with a coating.
Why use two pumps in the sump?
A dual pump sump has a second pump that takes over if the first fails or cannot keep up, which protects the room during heavy rain.
Does a cavity drain system need maintenance?
The membrane does not, but the pumps should be serviced regularly so the system keeps working as designed.
Thinking of using a cellar or vault?
Our CSSW and CSRT trained surveyors find the real cause before recommending any work. Non-invasive survey with a clear written report. No obligation.
Survey carried out by Lionel Sewell (FODCS) at Advanced Damp. Project completed in Canonbury, Islington, N1.
Sam Fitzgerald is the founder of Advanced Damp and a working damp and structural waterproofing surveyor diagnosing and treating moisture problems in residential and commercial properties across London and the South East. He is FODCS certified (a Federation of Damp Certified Surveyor) and a member of the Federation of Damp. His hands-on work covers rising damp, penetrating damp, condensation, basement waterproofing to BS 8102, and thermal imaging surveys, and he has personally completed over 400 damp surveys across properties of every type and age. Everything he writes draws directly from jobs he has carried out. He does not write about treatments, products or causes he has not dealt with first-hand in the field.
