Groundworks 1,403 views Sep 05, 2018
The challenge of waterproofing below ground structures

The waterproofing of existing below ground structures, particularly ageing ones, needs as much careful planning as a new-build project in terms of materials and process writes Stuart Benham. System options, however, tend to be more limited when it comes to putting a watertight seal on a basement or belowground area already in use.

In general, two systems are up for consideration as far as waterproof refurbishment is concerned. A Firstly a waterproof render solution, such as BBA approved Sika-1 Pre-bagged Structural Waterproofing System, is one popular option. This consists of a 3 coat render system for use on walls and overhead surfaces, and a screed system for use on the floor. Sika-1 pre-bagged ensures specifiers meet the requirements of a waterproofing project without the need for ongoing maintenance. The pre-bag system is factory-controlled quality, with each layer to the optimum mix ratio. Site batched versions should not be considered as the quality cannot be relied upon.

Cavity drain systems are also popular with retrofit waterproof installers. Sika® CD – Cavity Drainage System, for instance, controls water after it has penetrated a structure. Loose-laid  for flooring applications and attached to a wall with surface plugs in vertical installations, Sika® CD - Cavity Drainage System directs penetrating water into a drainage system and a collection sump before using a pump to discharge water from the building. This is also a proven, reliable system, but unlike the pre-bagged option, the cavity drainage system requires maintenance programme which at a minimum is annual A combination of both is also an option often used.

Early intervention

Existing fissures and cracks in the structure should be addressed at the earliest opportunity. Left untreated, defects could potentially lead to greater issues and costly, time-consuming repair. Failure to make good the structure at the earliest stage of deterioration could also affect the overall structural integrity of the building, which in-turn may adversely affect any waterproofing system installed.

For manufacturers, a key aspect of retrofit waterproofing is interaction and compatibility between different waterproofing interfaces. It’s a challenge Sika is able to meet, as it offers Type A, B and C systems - A (barrier protection); B (structurally integral protection); C (drained protection) - each of which can connect to form the highest-quality waterproof solution. As a full range provider, Sika is able to offer unbiased advice and tailor the solution to the requirement, thus avoiding specifying solutions unsuitable for the product.

As for contractors, the challenge is to ensure installation teams are sufficiently-skilled to correctly fit the waterproofing system. Through toolbox talks and site visits, Sika is able to offer full, technical support to installers. This is a value-added service which comes at no extra cost. In addition, contractors are able to obtain official recognition of their skills by becoming a ‘Sika-approved’ installer of as the  Sika-1 Pre-bagged system where candidates are vetted, trained and assessed before being given registered status. As well as having access to on and off-site technical support.  Only Sika 1 Registered contractors benefit from the Sika guarantee on the Sika 1 pre-bag product. With Sika Cavity drain systems, it is always best to use a specialist waterproofing contractor, but if the works are being done by a general contractor, Sika do offer site tool box talks and on site support as part of the guarantee process.

At your service

In terms of the specifier, the biggest challenge is ensuring the specified waterproofing product is fit for purpose and meets the required performance level. This is where - once again - Sika’s service offering comes to the fore. The company not only provides a range of watertight solutions for a host of concrete applications, its CSSW-qualified specification managers have a wealth of experience to offer expert guidance to ensure products are fit for purpose, specified and installed correctly. This helps ensure projects are completed successfully. Sika can also recommend specialist contractors for a particular scheme, whilst its guaranteed BBA-certified products assure users that they are in possession of goods of the optimum quality.