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Basement and cellar waterproofing, designed for the water that is there
A below ground room is holding back the ground and everything in it. Getting that right starts with establishing what the water is actually doing: whether it arrives with rainfall and drains away, sits against the structure as a water table, or is simply surface water that could be dealt with outside for a fraction of the cost.
What we establish first
- Whether the water is seasonal, episodic with rainfall, or permanently present
- Whether it is groundwater, surface water running at the building, or a defective drain
- What the surrounding geology is doing, since chalk, clay and made ground behave differently
- Whether existing drainage outside is failing before anything internal is considered
- Whether the space is being used in a way that needs full habitable standard at all
The three approaches
Cementitious tanking, a barrier applied to the structure, resists water directly. It works where the structure is sound and the hydrostatic pressure is modest, and it is unforgiving of movement, service penetrations and any part of the perimeter that is missed, because a barrier system is only as good as its weakest point.
Cavity drainage manages water rather than resisting it: a studded membrane holds any water arriving at the wall, a perimeter channel collects it, and a sump and pump take it away. It tolerates movement and imperfection far better, which is why it is the usual answer in high pressure situations. It also has moving parts and requires maintenance, which owners are frequently not told at handover.
External work is the third and the most overlooked. Improving ground falls, renewing gullies, fixing a drain and intercepting surface water above the building solves a surprising number of below ground damp problems for a fraction of the cost of either internal system. It should always be considered before anything is applied inside.
Where systems actually fail
Almost never in the membrane. The failures we are called to are silted perimeter channels, sump pumps that have never been serviced, float switches that have stuck, and details around service penetrations that were compromised by later work. Each is a fraction of the cost of the re tanking that is usually proposed.
The second common failure is a system specified for the wrong water. Tanking against a seasonally rising water table without drainage sized for it transfers the pressure elsewhere, and cavity drainage without a properly considered discharge point simply moves the water somewhere it will come back from.
Design, installation and maintenance
We survey the water before specifying the system, including the outside, and we say when the answer is drainage rather than waterproofing. Where a system is right, it is designed for the property, installed with proper attention to penetrations and junctions, and handed over with a maintenance schedule that says what needs servicing and how often.
The work carries an insured workmanship guarantee, with documentation you can hand to a buyer. Every project is documented so that future works to the room, a new radiator, a socket, a floor covering, do not compromise the waterproofing without anybody realising.
Find out what the water is doing before you specify a system
A survey of the below ground structure and the ground outside it, and a written report within 24 hours setting out what is actually needed.
Book a surveyOr call 07386 225526.
Questions
Our cellar has started leaking. Does the whole system need replacing?
Usually not, and this is the most common overspecification in this part of the trade. Cavity drainage systems have maintainable parts that fail long before the membrane does: channels silt up, sumps fill, pumps fail and float switches stick. Most of the failures we inspect are in those. We survey the whole system including the parts a re tanking quote tends not to mention, and report what has actually failed rather than what would be most profitable to replace.
Tanking or cavity drainage?
It depends on what the water is doing and on the structure. Tanking resists water and is unforgiving of movement and of any missed detail, so it suits sound structures with modest pressure. Cavity drainage manages water and tolerates imperfection, which suits higher pressure and older, less predictable structures, at the cost of requiring maintenance. The wrong choice is expensive either way, which is why the water is surveyed before the system is chosen.
Does a waterproofed basement need maintaining?
A cavity drainage system certainly does, and a great many owners are never told so. Channels need clearing, sumps need checking, pumps need servicing and battery backups need testing. An annual check costs very little and prevents the kind of failure that gets diagnosed as the waterproofing having failed. Any system we install is handed over with a schedule setting out what needs doing and when.