Waterproofing Liquid Membranes

A liquid waterproofing membrane is a polymer-based coating applied by brush, roller or spray directly to a substrate, curing in place to form a continuous, joint-free waterproof barrier. Unlike sheet membranes, which are manufactured to a fixed width and applied in overlapping panels, liquid applied waterproofing membranes conform to the exact shape of the surface they are applied to. This eliminates the laps and joints that are typically the primary points of failure in sheet membrane systems, making liquid membranes particularly effective on surfaces with complex geometry, penetrations, internal angles and details that are difficult to fully seal with sheet products.

In structural waterproofing, liquid waterproofing membranes are specified under BS 8102:2009 as Type A barrier systems, providing a continuous impermeable layer against a concrete structure to prevent groundwater and moisture ingress. Correctly specified and applied to a properly prepared substrate, a liquid waterproofing membrane is an effective and durable solution for below-ground and below-slab waterproofing. Performance is directly related to surface preparation quality and correct application thickness, both of which are within the control of a competent installer.

Liquid Waterproofing Membranes for Concrete and Below-Ground Structures

Liquid waterproofing membranes for concrete are applied directly to the prepared concrete surface after the structure has been formed, making them a post-applied waterproofing solution. They are suited to basement walls, retaining walls, below-ground floor slabs and other concrete substructures where a fully bonded, continuous waterproof layer is required across the external face of the structure.

Our range includes liquid applied waterproofing membranes from GCP and RIW covering both single-component and multi-component systems for structural below-ground applications. Single-component products are applied directly from the container without on-site mixing. Multi-component systems such as the RIW Flexi Seal Pro two-part product require mixing before application and are typically used where a higher specification or faster cure profile is required by the project.

Where the substrate or system specification requires it, a primer should be applied to the concrete surface before the liquid waterproofing membrane. Priming improves adhesion to the concrete, reduces the risk of application defects caused by substrate porosity, and forms part of the complete waterproofing system for certain products. The RIW Flexiseal Pro Primer is designed for use as part of the RIW Flexi Seal Pro system.

Liquid Gas Membranes

Where a structure requires protection against both groundwater ingress and ground gases, a dual-function liquid applied membrane can cover both requirements within a single application. The Visqueen Liquid Gas Membrane is a liquid applied product providing combined waterproofing and ground gas resistance, including methane, carbon dioxide, radon and volatile organic compounds. It is suitable for below-ground structures on sites where ground gas risk has been identified and a liquid applied solution is preferred over a pre-applied or self-adhesive sheet membrane alternative.

Applying a Liquid Waterproofing Membrane

Surface preparation is the most critical stage of any liquid waterproofing membrane application. The concrete substrate must be sound, clean, dry and free from laitance, dust, oil and loose material. Cracks, voids and construction joints should be addressed before the membrane is applied, liquid membranes applied over an unprepared or contaminated surface will not achieve the required adhesion or film thickness and will fail as a result.

Liquid applied waterproofing membranes are typically applied in a minimum of two coats to achieve the specified dry film thickness. The first coat is applied by brush or roller in one direction and the second coat applied perpendicular to the first once the first coat has cured sufficiently. Applying in two directions ensures consistent coverage and reduces the risk of thin areas that would compromise waterproofing performance across the membrane.

A correctly applied liquid waterproofing membrane on a below-ground structure is designed to perform for the lifetime of the structure. Failures are almost always attributable to poor surface preparation, insufficient film thickness or inadequate curing conditions rather than product failure itself.

As with any applied waterproofing system, correct installation practice is what determines long-term performance. Liquid membranes are applied wet and cure in place, so monitoring wet film thickness during application ensures the specified dry film thickness is consistently achieved across the whole area. Working within the manufacturer's recommended temperature and weather conditions supports correct curing and a fully performing membrane. Both are straightforward considerations for a competent contractor and form part of standard application practice on any structural waterproofing project.

Liquid Waterproofing Membranes vs Sheet Membranes

The choice between a liquid applied waterproofing membrane and a sheet membrane for a below-ground application depends on the geometry of the structure, the stage of construction at which waterproofing is applied, and the project specification.

Liquid waterproofing membranes have a clear advantage on surfaces with complex geometry, penetrations, pipework, internal angles and construction details where sheet membranes are difficult to fully conform to without cutting, lapping and detailing that introduces additional joint risk. A liquid membrane applied correctly to these details produces a continuous barrier with no joints or laps. On large, regular flat surfaces such as a straightforward basement wall with minimal penetrations, sheet membranes can be faster to install and provide a guaranteed manufactured thickness without the film thickness monitoring that liquid membrane application requires.

A liquid damp proof membrane applied correctly to a properly prepared substrate works effectively, the key variables are surface preparation, application thickness and curing conditions.

Why Choose Construction Supplies UK for Liquid Waterproofing Membranes

Liquid applied waterproofing for below-ground structures: From single-component brush-applied products to two-part systems and dual-function liquid gas membranes, we stock liquid waterproofing membranes from leading manufacturers for structural below-ground applications.

Trusted industry brands: Shop leading manufacturers including GCP, RIW and Visqueen.

Competitive trade prices: Liquid waterproofing membranes at competitive trade prices with no minimum order value.

Fast UK-wide delivery: Reliable nationwide delivery with free shipping on orders over £300.

Expert support when you need it: Our team can help you choose the right liquid waterproofing membrane for your project. Contact us at sales@constructionsuppliesuk.co.uk or call 03300 55 32 02.