ATi Damp SurveyHome / Services / Basement Damp
Basement damp: an independent view before you re-waterproof
London has more converted basements and lower ground floors than anywhere else in the country, and a re-waterproofing quote for one routinely runs into five figures. We survey them and write reports. We install no systems, tender for nothing and take no commission, which is the only sensible position from which to tell somebody their basement does not need redoing.
What usually turns out to be wrong
- A perimeter drainage channel silted up, which is a clearing job rather than a rebuild
- A sump pump that has never been serviced, or a float switch that has stuck
- A service penetration compromised by later work, letting water past an otherwise sound system
- A front lightwell decked, planted or paved over, bridging the wall from outside
- External ground and drainage sending surface water at the building in the first place
The London lightwell problem
Almost every Georgian and Victorian lower ground floor in London has a front lightwell, built specifically to keep soil off the wall and to let the structure breathe. A very large number are now decked over, filled with planters, used as bike stores or paved to make more usable space. Each of those bridges the wall at or above internal floor level and puts water exactly where the original design was keeping it away from.
Rear gardens raised by successive landscaping do the same at the back. Damp on a lower ground wall in London is very often ground level and drainage, and that is a spade and a gully rather than a waterproofing system.
Assessing an existing system
Where a system is installed, we assess the whole of it rather than the wall where the water appeared. Channel condition and fall, sump and pump operation, float switch function, battery backup where fitted, discharge route and whether it can actually discharge, and the detailing at every service penetration we can see.
That is a different exercise from inspecting a wet patch, and it is why our conclusion so often differs from a re-waterproofing quote. The membrane is rarely the thing that failed.
What the report gives you
A finding on what the water is doing, whether it is groundwater, surface water or a defect, and what has actually failed. Where an existing system needs work, what part of it and why. Where the answer lies outside the building, which is more often than people expect, the report says that and says what should be done.
ATi carries out no waterproofing, tenders for nothing and recommends no contractors. If a system genuinely does need replacing you will find that in our report too, and you can take it to whichever installer you choose knowing the scope was not written by somebody who would be paid to deliver it.
Get a second opinion before committing five figures
An independent survey of the below ground structure, the system if there is one, and the ground outside, with a written report within 24 hours of the visit.
Book a surveyOr call 020 3355 4944.
Questions
We have been quoted to re-waterproof the whole basement. Is that likely to be necessary?
Sometimes, and less often than it is quoted for. In the great majority of failures we inspect in London, the fault is in the maintainable parts of the system rather than the waterproofing itself: a silted channel, an unserviced pump, a stuck float switch, or a service penetration disturbed by later work. Those are a fraction of the cost. A survey that examines the whole system rather than the wet wall usually finds the difference between the two answers.
Our basement conversion was handed over with no maintenance instructions. Is that normal?
It is common and it should not be. A cavity drainage system has moving parts and needs servicing: channels cleared, sump checked, pump serviced, backup tested. Without that schedule the first failure typically arrives several years later with no maintenance history at all, and it is then presented as a failure of the waterproofing. Establishing that the system was never maintained rather than never adequate matters for both the remedy and any claim.
Could the problem be outside the building entirely?
Frequently, and in London the lightwell is the usual culprit. A lightwell built to keep soil off the wall, now decked, planted or paved, bridges the wall from outside and delivers water directly to it. Raised rear gardens do the same. Both produce persistent damp on a lower ground wall that no internal system will resolve, because the water is arriving above the level anything internal is protecting.