Getting water-proofing right

If you are installing a concrete basement or other below-ground structures, getting your waterproofing specification right to combat leaks is crucial, as they can undermine your entire project. Yassar Altaf from Sika answers readers’ questions on long-term approaches for controlling water

How does a render-based system compare to a cavity drainage system?

Unlike render products, cavity drain systems require ongoing maintenance. This incurs greater running costs, while the system itself requires more space to install. As for benefits, the cavity drain system acts as a vapour barrier and requires limited surface preparation. It can be used where the substrate does not have the strength to resist stresses caused by water pressure a pre-bagged render system can be argued to be a more cost-effective solution, over a lifespan of 60 years.

How can I get a waterproofing system without all the maintenance?

Taking a pre-bagged system for example, once applied there is no requirement for drainage products or equipment such as water pumps. Eliminating the need for revisiting the site means the system is extremely cost- effective. It bonds directly to the substrate and follows the contours of any structure. Some substrate preparation may be required, but once installed, it provides a hard-wearing surface capable of resisting damp and high water pressure.

What’s the system made up of?

Watertight renders and screeds, produced using mortars which consist of a blend of special cement and kiln-dried graded aggregates. The Sika-1 Pre-bagged waterproofing solution is packaged in four grades, each specifically designed for optimum application performance and durability. It consists of a render system for use on walls and overhead surfaces and a screed system for use on the floor.

Are there any limitations on where it can be installed?

The system is suitable for virtually any application, providing an effective watertight seal for structures that need to keep water out as well as structures that must keep water in such as swimming pools. The system is suitable for applications in both new build and refurbishment projects.

How did the system originate?

The Sika system has been in use for 100 years, originally as a quick-setting waterproofing admixture for mortar, used to waterproof the Gotthard Tunnel in the Swiss Alps. The project enabled the Swiss railway company to electrify a vital connection between northern and southern Europe.

What are the industry accreditations?

It is available as a BBA-approved structural waterproofing system and classified as a Type A internally applied waterproofing system according to BS 8102-2009. It also has Drinking Water Inspectorate approval and a guarantee is provided when the product is installed by a registered Sika waterproofing contractor.

Yassar Altaf is head of product and marketing at Sika’s Concrete & Waterproofing division