Basement Waterproofing
Below-ground water ingress in basements, car parks and retaining walls, including where excavating back to the outside face is not an option.
Below ground, the water is always trying
Above ground, waterproofing sheds water. Below ground it holds water back, under constant pressure, with nowhere for it to drain away to. That difference is why a defect in below-ground tanking behaves nothing like a defect in a roof: it does not leak when it rains, it leaks permanently.
The usual first signs are damp patches on walls, efflorescence blooming out of a construction joint, rust staining on a slab soffit, or a car park that never quite dries out.
Because these leaks come under pressure, they frequently arrive with concrete damage - spalling, or corroded reinforcement behind it. Waterproofing over that hides a structural problem rather than fixing one, so the concrete is repaired as part of the same job.
How the work runs
Not every job needs every step. What it does need is established before you are asked to approve anything.
Trace the ingress
Establish where water is entering the structure - a joint, a penetration, a crack or a failure in the original tanking.
Assess the concrete
Spalling, cracking and reinforcement condition, because below-ground leaks and concrete damage almost always arrive together.
Repair the structure
Concrete repair and reinforcement treatment first. Nothing gets waterproofed over damaged concrete.
Treat the ingress path
Crack and joint injection where water is coming through the structure itself, which has to hold against pressure rather than shed it.
Apply the tanking system
Negative-side treatment where excavation is not practical, or reinstated external tanking where the outside face can be reached.
Monitor and hand over
Checked over a wet period where the programme allows, made good, and handed over with the documentation and warranty.
Frequently asked questions
Below ground, water is under constant pressure against the structure rather than running off it, so any defect in the tanking, a construction joint or a penetration becomes a permanent path rather than an occasional one. Damp patches, efflorescence and rust staining on the slab soffit are the usual first signs.
Often, yes. Where digging back to the outside face is not practical - which in a built-up site it usually is not - the treatment is applied from the inside, using systems designed to hold back water under pressure rather than shed it. Which approach applies depends on the structure and where the water is entering, so it is established on site first.
Yes. Below-ground leaks frequently come with concrete cancer, spalling or corroded reinforcement, and waterproofing over damaged concrete just hides it. As a registered building practitioner we carry out the structural repair and the waterproofing as one job.
It is staged. Car parks and plant rooms usually stay partly in use, with the work sequenced bay by bay so parking and access are not lost at once. The scope and the staging are set out in writing after the assessment.