2/17/2012: Suitable Applications For Specifying Strip Applied Waterstops
Strip applied waterstops can offer several advantages over a traditional PVC profile if they are used in the proper application.
Traditional PVC profiles must be installed prior to your first concrete pour, and need to be properly secured to ensure that they do not shift during concrete placement. In many applications this will require the utilization of split forming to allow half of your profile to penetrate into your second pour. Traditional PVC profiles must also be heat welded with a specially made splicing iron at intersections and whenever a new roll of material must be started. These intersections can be quite elaborate requiring mitered cuts to ensure that the profiles match together properly, with the purchase of factory made fabrications most often being the best alternative to welding difficult intersections in the field. Strip applied waterstops can offer several advantages over a traditional PVC profile if they are used in the proper application. Also, if you have an existing concrete structure that you are pouring against, a traditional PVC profile will not be suitable and a much more time consuming and labor intensive retrofit profile will need to be utilized in order to install a PVC waterstop.
Strip applied waterstop is installed after the first concrete pour, thus eliminating the need for split forming or carefully securing the profile to adjacent rebar. This also makes it possible to install to existing concrete eliminating the need for retrofit profiles. Depending on the type of strip applied waterstop that is selected, intersections are simply overlapped or bonded together using an adhesive, rather than the heat welding that requires the use of a special welding iron.
However, strip applied waterstops do have their limitations and it is important to make sure that your application is suitable before specifying one. Hydrophilic strip applied waterstops such as our Hydrotite, Sikaswell A, and Swellstop expand when exposed to water and create a compression seal in your joint to prevent water migration. It is this swelling pressure that creates a watertight joint, therefore any joint in which movement is expected is not suitable as you will not be able to maintain the pressure needed. Therefore in order for hydrophilic waterstops to perform properly it is recommended that the joint be tied together with the reasonable expectation that you will not experience movement. This swelling pressure can also cause the concrete to “blow out” if the hydrophilic waterstop is installed without the proper concrete coverage, which is why it is critical that the minimum coverage depth is specified and adhered to (hydrotite and swellstop both require a minimum of 2”).
Hydrophilic waterstops are also best suited for applications in which they will remain continuously wet, as they will shrink down to their original size when allowed to dry, thus losing your compression seal. While they will swell when exposed to water again, this process will take time and your joint will not be watertight until a proper swelling pressure has been achieved.
Finally, it is important to note that Hydrophilic waterstops such as our Hydrotite, Sikaswell A, or Swellstop require exposure to water in order to swell. Exposure to any other liquid will not necessarily cause the material to swell, and could actually cause the material to break down or even shrink. Therefore strip applied waterstops are generally not recommended for chemical containment applications.
There is not a single waterstop that is perfect for every application. Sika Greenstreak offers several different types of strip applied waterstops along with our traditional profiles and each have their advantages that make them ideal for various applications. If you are interested in learning more about which type may be best suited for your application, please contact one of our engineers who will be happy to assist you in making sure you have specified the material and shape that is going to work best on your project.