Waterproofing Joint Sealants & Fillers

Construction joints, movement joints and expansion joints in below-ground concrete structures are among the most common points of water ingress in waterproofed buildings. Where the concrete itself can be made effectively watertight, joints between pours, between structural elements and at service penetrations require dedicated waterproof joint sealants and fillers to maintain the continuity of the waterproof barrier. The range at Construction Supplies UK covers the principal product types used for concrete joint waterproofing in below-ground construction, from hydrophilic strips installed during the initial build to poured sealants applied to existing joints and rapid-setting compounds used to arrest active leaks. Products are available from GCP, Sika, Fosroc and Natural Cement.

Hydrophilic Swelling Waterstops

Hydrophilic swelling waterstops are pre-formed strips or profiles installed within construction joints before the concrete pour. On contact with water, the material absorbs moisture and expands, compressing against the surrounding concrete to form a watertight seal within the joint. They are the standard specification for construction joints in below-ground reinforced concrete structures, including basement walls and floors, retaining walls, tunnels and water-retaining structures, where a reliable, long-term seal is required at the joint between successive concrete pours. GCP Bentorub Waterstop is a sodium bentonite-based hydrophilic strip for use in construction joints in below-ground concrete structures. It is installed directly onto the prepared concrete surface before the adjacent pour, with the bentonite expanding on contact with groundwater to seal the joint.

GCP Adcor 500S is a hydrophilic swelling waterstop in strip form, suitable for construction joints in below-ground and water-retaining concrete structures. SikaSwell S-2 is a one-component, moisture-curing swelling sealant applied by gun to construction joints, expanding on contact with water to fill and seal the joint profile. SikaSwell A is a pre-formed rectangular acrylic swelling profile for construction joints and service penetrations in concrete structures, requiring a minimum of 80mm reinforced concrete cover and suitable for static construction joints only, not movement joints.

Hydrophilic waterstops are installed during construction and cannot be retrofitted into an existing joint without breaking out the surrounding concrete. Where joint sealing is required on an existing structure, a poured sealant or injected system is the appropriate approach.

Joint Fillers and Poured Sealants

Joint fillers and poured sealants are used to seal construction joints, movement joints and expansion joints in concrete structures, either during construction or as part of remedial sealing work on existing joints. GCP Aerofill 1 is a compressible, closed-cell polyethylene foam backer rod used to fill and support sealant in joints prior to the application of a poured or gun-applied waterproof joint sealant. It controls the depth of sealant application and ensures the correct width-to-depth ratio for sealant performance, preventing three-sided adhesion and allowing the sealant to move freely with joint movement.

Fosroc Colpor 200PF is a two-component, cold-applied polyurethane joint sealant for sealing movement joints and construction joints in concrete floors, roads and other trafficked surfaces. It provides a durable, flexible, waterproof seal that accommodates joint movement and resists fuel, oil and hydraulic fluid spillage, making it particularly suitable for garage forecourts, parking areas, cargo bays and other surfaces where chemical exposure is likely.

Stopping Active Water Ingress at Concrete Joints

Where water is actively entering through a joint or crack at the time of repair, a standard sealant or waterstop cannot be applied until the flow is arrested. Natcem Waterstop is a rapid-setting, expanding cementitious compound for plugging active water leaks in concrete and masonry. It sets within minutes of application, allowing the leak to be stopped quickly before the main joint sealing or waterproofing system is applied. It is suitable for use on construction joints, cracks and pipe penetrations where water ingress needs to be controlled before remedial work can proceed.

Choosing the Right Waterproof Joint Sealant or Filler

The appropriate product depends on whether the joint is being sealed during construction or as a remedial measure on an existing structure, and on the nature and movement of the joint. For construction joints in new below-ground concrete, hydrophilic swelling waterstops are the standard specification. GCP Bentorub and GCP Adcor 500S are installed as pre-formed strips before the concrete pour. SikaSwell S-2 is the gun-applied alternative where a formed strip is not practical. SikaSwell A is used where a pre-formed acrylic profile is preferred for static construction joints with adequate concrete cover.

For movement joints and expansion joints in concrete floors and trafficked surfaces, Fosroc Colpor 200PF provides a flexible, durable waterproof concrete joint sealant that accommodates movement. GCP Aerofill 1 backer rod should be used in conjunction with Colpor 200PF to control sealant depth and ensure correct joint geometry.
Where active water ingress is present, Natcem Waterstop should be used to arrest the leak before any other joint sealing product is applied.

All products in this range are suitable for use in below-ground concrete joint sealing applications. Where hydrostatic water pressure is present, a full Type A barrier waterproofing system may also be required in addition to joint sealing.

Why Choose Construction Supplies UK for Waterproofing Joint Sealants and Fillers?

Specialist joint waterproofing products: From hydrophilic swelling waterstops for new construction to poured joint sealants and rapid-setting leak-stopping compounds, we stock products covering the full concrete joint waterproofing process.

Trusted industry brands: Shop GCP, Sika, Fosroc and Natural Cement from stock.

Competitive trade prices: Waterproofing joint sealants and fillers 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 specify the right joint waterproofing product for your project. Contact us at sales@constructionsuppliesuk.co.uk or call 03300 55 32 02.