Capillary active waterproofing? (for concrete).

Concrete is not generally waterproof.  Pores and cracks within will let water through and the age old problem is how to stop it.

Most methods involve sticking a layer of something other than concrete on one side of the slab/wall or another.  Usually these are bitumen based, with little affinity for damp concrete.  Applying them requires skill, experience and patience too – it can be tricky.

Unfortunately, building sites are dirty places and life can be hectic for the ground workers, who are usually those tasked with the waterproofing job. I’ve tried to use some of these products in a trench and I can tell you – they have a hard job.

If applied correctly these products work, but as they are in effect thin coatings, they can be damaged, torn, peel off or be missed.  In practice, once trenches are filled-in and walls are built, there is no way of checking for leaks or repairing them if there are leaks.  Failures do happen.

Anyway, we’ve used pore blocking mortar injection DPC’s for years, but until recently most of the waterproofing we did involved ‘tanking’ concrete, with Vandex BB75, Unimortar 1 or type C cavity drain membranes.

A month or two ago we applied Vandex Super to the upper face of a structural floor slab for a basement.  Apparently, a bentonite mat, installed under the slab had been suggested, but this was overruled.  So we found ourselves shot blasting the surface and then scrubbing in the Vandex. Vandex Super is what is known as a Capillary Active material….huh?  This means that intimate contact with the concrete is essential if the materials are to ‘get it on’. Hence the enclosed shot blasting.

We gave the product five days to cure and lifted the PVC covers.  The spotty and slightly salty looking surface didn’t look so impressive, but ‘hey’, it was to be covered by a vapour check and insulation anyway, so no matter.  Then the heavens opened….for several days.

Boy is that stuff good.  The basement was turned into a fish tank; not a drop of the rain soaked in.  We had to vac it all out in order to finish the job. The Vandex reacts with free lime in the concrete, forming crystalline growths in the pores, which make the concrete waterproof, in depth.  Best of all, the waterproofing is then integrated and cannot be removed.  It even re-grows into cracks if they occur later.  Bloody clever these Swiss engineers; must be all tunnels and hydro electric dams they work on.

If you’ve not used it before I’d recommend a look, next time really waterproof concrete is needed.  Application is easy – some care is required and of course, on most jobs it will need careful integration with other elements, so a specialist is needed – works a treat. Works on older concrete too, though more prep may be needed.

Have a look at the data sheet here

See my guys working with it below

Dry Rot.

Copyright © 2010 Preservation Expert. Legal Stuff: All the advice and information in the posts on my blog is made in good faith and is based on my experience and knowledge at the time of writing. However, nobody is infallible and whilst I’m confident that most of what I write about preservation issues is accurate, there’s a good chance there’ll be an error or two somewhere. I do change my mind about stuff, as I gain more experience. In view of this you must make your own decisions on whether to follow any advice I write and think about this; I could be wrong. No responsibility will be accepted by the author for any losses anyone may suffer as a result of any mistake or for the consequence of any action you take as a result of reading this blog. If you do suffer a loss, resulting from anything I’ve written, a verbal heartfelt apology will be your only compensation.