Base Seal with Tear Web - PVC Waterstop

About the Base Seal with Tear Web Profile

Base seal with tear web waterstops are specified for movement joints where the waterstop is installed along the exterior face of the concrete rather than embedded across the joint. The flat base sits against the form or substrate on the water side of the structure, while the tear web rises over the joint and is engineered to rupture as the joint opens — allowing the U-bulb to deform without placing the PVC in tension. This combination of base seal placement and tear web geometry accommodates lateral, transverse, and shear movement while keeping the waterstop on the positive (water) side of the joint.

Larger tear web bulbs are generally associated with greater joint movement capacity. The base seal configuration is well suited to slab-on-grade joints and backfilled walls, where the waterstop can be positioned against the formwork or earth side and then encapsulated as concrete is placed. Base seal profiles have some limitations with transitions and intersections, so factory-fabricated fittings are particularly important for changes of direction.

Typical Applications

✓Commonly Specified For

Slab-on-grade movement joints
Backfilled wall joints with exterior-side waterproofing
Expansion and contraction joints with significant movement
Joints subject to lateral, transverse, or shear movement
Water and wastewater treatment plants
Reservoirs, tunnels, and containment structures
Potable water contact applications
Texas Highway Type A specifications

→Other Profiles May Be Considered When

The waterstop will be embedded across the joint — see Ribbed Centerbulb or Ribbed Tear Web
Moderate joint movement with simpler geometry is acceptable — see Base Seal
The joint has continuous reinforcement and minimal movement — see Flat Ribbed
The joint is at an existing concrete face — see Retrofit profiles
Complex transitions and intersections are required throughout the project

Profile selection should always be verified against project specifications and engineering requirements. Contact us if you’d like assistance reviewing options for your application.

Available Sizes & Versions

Sika Greenstreak produces the base seal with tear web waterstop in a single profile configuration.

Profile 772

Width: 9″

Tear Web Height: 2″

Weight: 1.85 lb/ft

Head Pressure: 100 ft (299 kPa)

Spec: Texas Hwy Type A

Sizing considerations generally include expected joint movement, hydrostatic head, and concrete cover. Contact us if you’d like help cross-referencing a profile against your spec.

Installation Overview

Base seal with tear web waterstops are installed along the exterior (water-side) face of the concrete rather than embedded across the joint. The flat base is positioned against the formwork or substrate, the tear web is centered over the joint location, and concrete is placed to encapsulate the base. Heat welding is generally the recognized method for splicing PVC waterstop, and factory-fabricated transitions are particularly important for base seal profiles given their limitations at intersections. Always refer to the manufacturer’s installation guide and project specifications for complete instructions.

Position

Lay the flat base against the formwork or substrate with the tear web centered over the eventual joint location.

Secure

Anchor the base to the form or substrate to prevent shifting during concrete placement.

Splice

Heat-weld butt splices in the field. Factory fabrications are strongly recommended for changes of direction.

Pour

Place and consolidate concrete to fully encapsulate the base while keeping the tear web aligned over the joint.

Frequently Asked Questions

+What’s the difference between a base seal and an embedded waterstop?

A traditional embedded waterstop is installed across the joint with roughly half the profile in each pour, forming a diaphragm through the thickness of the concrete. A base seal waterstop is installed along the exterior face of the concrete on the water side, with the flat base anchored against the form or substrate. Base seal profiles are easier to position with single-sided formwork and are commonly used in slab-on-grade and backfilled wall applications. They do have some limitations with transitions and intersections compared to embedded profiles.

+How does the tear web work?

The tear web is intentionally designed to rupture as the joint opens. The thin web is a sacrificial element. Once it tears, the U-bulb is free to deform and stretch without the PVC being placed under tension, which is what allows tear web profiles to accommodate larger movements than a centerbulb of similar size. The watertight seal is maintained by the deformed U-bulb and the flat base encapsulated in the concrete.

+Can profile 772 be installed in a vertical wall joint?

Yes, base seal with tear web profiles can be installed on vertical wall surfaces as well as horizontal slabs. The base is anchored against the formwork or substrate on the water-side face of the wall, with the tear web aligned over the joint. This makes it a common choice for backfilled walls where waterproofing is needed on the exterior face.

+Why are factory fabrications especially important for base seal profiles?

Base seal waterstops have some inherent limitations with transitions and intersections because the flat base geometry doesn’t lend itself as cleanly to L’s, T’s, and crosses as a symmetrical embedded profile does. Field-fabricated intersections are widely cited as a leading cause of waterstop performance issues across all profile types, but the limitation is more pronounced with base seal shapes. Sika strongly recommends factory-made fabrications for any change of direction.

+Is profile 772 suitable for potable water structures?

All Sika Greenstreak PVC waterstop profiles, including profile 772, are NSF/ANSI 61 certified for potable water contact. This makes it appropriate for many applications such as finished water reservoirs and treatment plant clearwells, subject to project-specific requirements.

+How is base seal with tear web waterstop welded in the field?

PVC waterstop is typically heat-welded using a thermostatically controlled splicing iron. The two ends are squared, butted against the heated blade until the PVC begins to melt, then pressed together and held until cool. Sika offers a Waterstop Welding Certification Program for contractors seeking formal training, as weld quality has a significant impact on long-term performance.

Sika Base Seal with Tear Web