Don't just rely on their tanking slurry alone.
We bought Construction Chemical's tanking slurry because they particularly boast:
'High Water Resistance:
Salt Resistance: The presence of salts in below ground situations can cause expansion when drying and lead to de-lamination at worst and efflorescence. Two components contained in the product actually react with these soluble salts turning them into solids that do not exhibit efflorescent or hygroscopic effects.
Set Control: ...This ensures that even in areas where there may be water movement the slurry sets quickly whilst allowing a reasonable period for application... ...Construction Chemicals Tanking Slurry is manufactured to have to a high level of performance in any situation where lateral or penetrating dampness is found. It has been carefully formulated to ensure that it is not affected by the problems normally associated with water movement such as salt damage and movement.
Water Based: Safe to apply on damp surfaces.
Tried and tested over many years with no failures.
High quality polymers give flexibility, salt resistance and good adhesion.
Unlike some products all the ingredients for this product to work are in the bag, the operator only requires water for mixing.
High alumina cement gives good salt resistance.'
Okay, that was enough for us. We bought it for our cellar and applied an SBR bond first, waited until it was tacky and then applied 2 coats of slurry, 1 horizontally and 1 vertically.
Imagine our surprise then when it didn't dry out! After several days and for several days, we manually dried it out with a fan but the damp kept coming back. They say on their website:
'Construction Chemicals Tanking Slurry is a sophisticated cementitious formulation designed for use in below and above ground waterproofing situations. The product is made up of many components, which give high water resistance, flexibility, salt resistance, good adhesion and set control in a form that only requires water for mixing.
Unlike other Tanking Slurries seen on the Internet this product does not need the addition of an SBR Bonding Agent Our Tanking Slurry has a pre-mixed polymer therefore eliminating the need, and extra expense, of adding polymer (SBR) to ensure optimum performance.'
This didn't make sense. Surely we couldn't be the only fail they've ever had!
On contacting Construction Chemicals and sending photos, we were told:
'Sometimes salt is difficult to see. It’s hard for to tell what the problem is, I would suggest salt may be the problem as it is lower down we’re the damp is.
What to do? I would suggest treat with anti salt, re prime with SBR add a little cement and then reapply another coat of Tanking. Hope that helps.'
After asking for clarification of the above instructions, we were told:
'Anti salt can be purchased from ourselves. Apply this to the wall as per the instructions.
Add just a handful of cement to 5l of watered down SBR.
Apply more tanking when the SBR is tacky.'
So, what we'd say is buyer beware as, even though they initially say that that their slurry combats water and salt, above and below ground, and that you don't need to buy SBR: Their tanking slurry alone may not actually do the job and you should first treat the wall with anti salt, SBR and cement - just in case - or apply it afterwards if it does fail and then slurry again!
Unfortunately, we only had to use this on the lower half of the wall and, believing that it would work, have already started cladding the uppper half of the wall and so adding an extra layer to the bottom is no longer an option for us. We have therefore had to buy Zinsser Watertite Waterproof paint, in the hope that this will solve the problem.