Frequently Asked Questions

Should SikaSwell be placed at the centre of the concrete section or at a specific depth from the water-facing side of a 250 mm thick basement wall?

SikaSwell should be placed at the mid-point of the concrete section — at 125 mm from either face of a 250 mm thick basement wall. The reason for central placement is to ensure that the SikaSwell strip, when it expands in contact with any water that penetrates the joint from the water-facing side, is surrounded by adequate concrete cover on all sides. If placed too close to the water-facing face (less than 60 to 75 mm from the wet face), the thin concrete cover is insufficient to provide the confinement pressure needed for the SikaSwell to generate its rated sealing compression — the strip may simply push out the thin concrete layer rather than sealing the joint under high hydrostatic pressure. If placed too close to the dry face (interior side), the water must travel through too large a portion of the joint cavity before contacting the strip, increasing the risk of significant water ingress before the seal activates. The practical installation procedure on a 250 mm wall: after the first pour has set and the top surface has been prepared clean, fix the SikaSwell strip to the centre of the construction joint contact face (125 mm from the formed concrete edge) using SikaSwell Adhesive or 6 mm diameter mechanical pins at 250 mm centres along the strip length. Butt-join the strip ends tightly and seal the butt joints with SikaSwell M-2200 mastic. Pour the second lift of concrete over and around the embedded strip.

Can SikaSwell be used as the only waterproofing measure at construction joints in a basement without installing Sika Waterbar PVC waterstop?

SikaSwell can be specified as the sole joint sealing measure at construction joints in low to medium hydrostatic pressure basements (groundwater head up to approximately 3 to 4 metres), provided the concrete structure is well-constructed (adequate wall thickness, low-permeability concrete, proper vibration and curing) and the construction joint faces are properly prepared before the second pour. For a single-basement structure in areas of Ghaziabad and Noida with moderate groundwater at 2 to 3 metres below ground (groundwater head at the slab level of 0 to 2 metres), SikaSwell alone at construction joints is a practical and cost-effective specification for standard building basement work. The advantages over PVC waterstop are: lower installation cost (simpler installation without wire-tying, no specialist formwork modifications), no risk of the waterstop being displaced during concrete vibration (a major failure mode of PVC waterstops on Indian sites), and compact profile that does not crowd the reinforcement in narrow concrete walls. However, for the highest criticality joints in structures where water leakage would be a major problem — pharmaceutical, data centre, or archive basements; underground transport infrastructure; water treatment containment; or basements with groundwater head above 4 metres — specify both Sika Waterbar PVC waterstop (primary barrier) AND SikaSwell strip (secondary barrier) at the same joint for a fully redundant dual-barrier system. Contact Space Arc Engineering for a project-specific joint waterproofing recommendation.

What happens if SikaSwell strip is accidentally wetted before the second concrete pour is placed — does it lose its sealing capacity?

Pre-wetting of SikaSwell before the second concrete pour is a real risk on Indian construction sites, particularly during monsoon season or on sites with active groundwater or surface water ingress into the excavation. If SikaSwell is wetted and allowed to swell before the second concrete pour is placed, the pre-swollen strip presents two problems: the pre-expanded strip occupies a larger volume than its original profile, creating difficulty in pouring concrete around it without damaging the expanded material; and if the strip then dries back and shrinks before the concrete is placed, the dried, shrunken strip occupies a volume smaller than its installed position in the joint, creating voids around the strip face that reduce the effective seal. Sika addresses this risk by supplying SikaSwell P-2002 in a controlled-swelling formulation that has a built-in delayed swelling characteristic — the strip does not start significant swelling until approximately 2 to 4 hours of continuous water contact, rather than swelling immediately on brief rain contact. If SikaSwell has been briefly rained on but not submerged or continuously wetted, it will typically be acceptable for use in the joint. If the strip has been submerged in standing water or monsoon flooding for more than 2 to 4 hours and shows visible pre-swelling (visible size increase), the affected length of strip must be replaced before the second pour. On monsoon-season basement pours, protect the installed SikaSwell strip with polythene sheet tape until immediately before the concrete pour.