For those who don’t really get a chance to see what this method of waterproofing involves, I’ve shot this short video on a site earlier today on a basement waterproofing site in Sowerby Bridge, West Yorkshire.. It shows an existing basement room with the CDM and drainage in place – only the floor membrane is to be completed, before the plasterers, joiners and services go back in.
The big advantages of a type C system, as opposed to type A tanked protection are:
The system will not change the dynamics of the water head – no hydrostatic pressure increase or shift
Minimal preparation – no need to scabble or sand blast
Fast drying – only a thin skim of plaster on the boards, no multiple dense layers of cement
Excellent insulation value – condensation is not increased.
It is quite forgiving, subject to a few important exceptions.
It is fast too.
On the minus side, membranes like these are not too clever for soffit details or complex detailing, hence we also use Vandex cementitious waterproofing, often alongside Oldroyd membranes. It really is horses for courses.
Good specification is key, so use a properly qualified person to survey and inspect – CSSW is the preferred qualification to look for and ideally any installer should be members of the PCA (Property Care Association), structural Waterproofing group, so that GPI insurance can be issued to cover the installers guarantee; in case his business fails. Whilst basement work is not rocket science, it is a minefield and the consequences of on-site carelessness or corner cutting can be horrendous.