Expert definitions of 40 technical terms from waterproofing and damp-proofing. Crystalline, injection, negative/positive-side waterproofing and more.
This glossary defines the 40 technical terms you will come across in waterproofing work, written from a specialist’s viewpoint. Use the alphabetical index to learn what crystalline waterproofing, acrylate gel injection, negative/positive-side waterproofing, capillary action and efflorescence mean, when each is used and how they differ.
A water-based chemical gel injected into cracks and joints with active water ingress. On contact with water it swells and stops the leak within seconds. The preferred method for no-dig, negative-side waterproofing of existing buildings.
A visible leak where water reaches the building surface continuously or intermittently. Unlike a dormant crack it demands immediate attention; passive waterproofing measures fall short — resin injection is essential.
A method that blocks water from entering the structure with a physical membrane layer — bituminous sheet, EPDM, TPO or a liquid-applied membrane. Classified as Type A (barrier protection) under BS 8102 and used in positive-side waterproofing.
A hot-applied, asphalt-based sheet membrane, generally used for positive-side waterproofing beneath foundations or on terraces. Mechanically robust, but it needs a protective layer against UV exposure.
An internal gutter system that collects and discharges water between a roof, balcony or garden wall. When it blocks or its waterproofing fails, water leaks into the structure — it calls for specialist detailing solutions.
The European standard for the protection, repair and strengthening of concrete structures. In waterproofing work it is the proof that both the material and the application method are fit for purpose.
The movement of water molecules upwards through the microscopic pores of a material, driven by surface tension against gravity. It is the physical mechanism behind rising damp.
A barrier coating of cement, quartz sand and special polymer additives, applied by brush, trowel or spray. Suitable for water tanks, bathrooms, terraces and many other substrates.
A junction between two concrete pours where insufficient bond has developed. It creates a structural weakness and a critical water leakage point.
A polymer-modified mortar used to reinstate damaged, corroded or cracked concrete to structural soundness. A critical surface-preparation step before any waterproofing is applied.
A dormant crack no longer moves and stays dry; an active crack opens and closes with structural movement and lets water through. Active cracks call for a flexible injection material such as polyurethane.
A cementitious chemical coating that penetrates the pores of the concrete and reacts to form a needle-like crystal structure. One of the few methods that can be applied from the negative (internal) side.
Persistently high relative humidity inside a building, or surfaces that stay permanently wet. It is caused by inadequate ventilation or a failure in the waterproofing.
A silicone-based chemical barrier injected horizontally at the base of a wall to stop rising damp — a retrofit damp proof course (DPC). It blocks capillary water from travelling up through the pores.
The controlled removal of groundwater collecting around the structure. A drainage system is the natural complement to long-lasting basement waterproofing.
A white, powdery salt deposit forming on a concrete surface. As water passes through the concrete it carries dissolved minerals to the face — visible evidence of an active leak.
A synthetic rubber membrane based on ethylene propylene diene monomer. Resistant to UV, ozone and thermal shock; used for terrace and roof waterproofing.
A controlled gap left in a structure to prevent damage from thermal movement, earthquakes or settlement. Its waterproofing is achieved with flexible profiles and elastomeric materials.
The ground-bearing concrete slab at the lowest level of the building, sitting over the foundation. It needs negative- or positive-side waterproofing to protect it from groundwater.
The body of water within the soil whose level changes with the seasons, exerting hydrostatic pressure on the structure. The principal reason basement waterproofing is required.
The proportion of water vapour in the air, outdoors or inside a building. When relative humidity stays above 65%, mould growth, material decay and health problems begin.
The static pressure a column of liquid can exert. It is the force groundwater applies to a basement retaining wall — the main load a negative-side waterproofing system must withstand.
A metal or plastic fitting fixed over a crack or joint, through which the injection pump delivers the chemical material at high pressure.
A polyurethane, acrylic or bitumen-emulsion waterproofing material applied by brush or spray, curing to a seamless, flexible film.
Fungal colonies that multiply on permanently damp surfaces, appearing as black, green or grey patches. Mould causes both surface damage and respiratory health risks.
Waterproofing applied from the side opposite the water — that is, from inside the building. The only practical solution for existing buildings where excavation is impossible; delivered with crystalline coating plus resin injection.
A waterproofing method applied from inside the building, without excavating the soil outside. Another name for negative-side waterproofing — unavoidable where buildings adjoin one another.
Protective waterproofing applied under dry, stable conditions where no active leak is present. Membrane systems and standard brush-applied coatings are typical examples.
An injection material that foams and expands on contact with water, stopping an active leak within seconds. On moving cracks it stays more flexible than acrylate gel.
Waterproofing applied on the side the water comes from — the outside of the structure. The ideal method, but it requires excavation and cannot be carried out where buildings adjoin one another.
The load-bearing external basement wall in direct contact with the ground. It is the surface exposed to the most intense water pressure.
Chronic moisture rising from the ground into the lower sections of walls by capillary action. It is cured with a horizontal injection barrier — a chemical DPC — at the base of the wall.
A cement layer laid over the structural floor to level it and prepare it for the finish. The waterproofing membrane usually sits beneath the screed.
The separation of coarse aggregate during a concrete pour, leaving voids behind. These voids are prone to water passage and must be repaired before waterproofing is applied.
The process of reinstating structural damage in a concrete element — cracking, spalling, delamination — with bonding resins, cement mortar or carbon-fibre reinforcement. Mandatory before any waterproofing.
The cleaning, render and paint removal, mechanical abrading and repair carried out before waterproofing. The most critical stage for the adhesion of the system.
Waterproofing the top-floor terrace or flat roof surfaces against rain and snow. Carried out with EPDM, TPO or bituminous membranes; a protective layer on top is essential.
A heat-weldable synthetic membrane based on thermoplastic polyolefin. Lightweight with high UV resistance; used on extensive green roofs.
Concrete produced with a crystalline admixture in the mix, providing waterproofing in its own right from the moment it is poured (BS 8102 Type B). Preferred for water tanks, tunnels and foundations.
Interior spaces in constant contact with water — bathrooms, WCs, kitchens. Under-screed waterproofing is mandatory because of the intensity of water use.
İMG service pages covering the on-site application of the methods and materials in this glossary.
A no-dig solution: crystalline coating plus acrylate gel injection.
DetailsA DampStop horizontal injection barrier that cuts off capillary movement.
DetailsPositive-side roof and terrace waterproofing with EPDM, TPO and bituminous membranes.
DetailsAdded to the mix as it is poured, it makes the concrete permanently watertight.
DetailsInstant, permanent sealing of active cracks and joints with a water-based gel.
DetailsLet us assess on site how the terms in this glossary apply to your building. Our technical team will get back to you for a comprehensive survey and report.
