Hold back hydrostatic pressure from the dry side.
Negative-side waterproofing is the technique used when you cannot get to the wet face of the structure — basement walls already poured against earth, lift pits flooded by groundwater, retaining walls leaking after the fact, and tunnels where excavation is no longer an option. Instead of sealing the surface water touches first, negative-side systems form a barrier on the dry side and resist the hydrostatic pressure trying to push through.
The two workhorse chemistries are crystalline and cementitious. Crystalline products react with free lime in the concrete to grow microscopic crystals deep inside capillaries, permanently blocking water paths while leaving the substrate breathable. Cementitious slurries form a thick, rigid coating bonded to the wall — fast to apply, paintable when cured, and capable of holding back several metres of head when correctly specified. For active leaks, hydraulic plug cements set in under three minutes and stop running water on contact, giving you a dry surface to coat over.
Our negative-side range is built around the brands engineers actually nominate: Drizoro Maxseal Flex and Maxplug for cementitious and plug work, plus crystalline admixtures and surface treatments for new and existing structures. Every product comes with the technical datasheet and a contactable applicator hotline so questions get answered before the slab is poured, not after.
Specifying tip: negative-side is a fix and a complement, not a substitute. New builds should always be tanked on the positive side first. Where that wasn't possible — or where a building has aged into a problem — negative-side systems are the most cost-effective way to dry out a structure without excavation.