Making sure rising damp won’t cause your tiling installation to fail
If you are tiling onto a substrate that is laid directly onto the ground, you need to find out whether a damp proof membrane is present or not. The membrane acts as a barrier to stop salts, such as sulphates, dissolved in water rising through the substrate to the cement-based adhesive and attacking it. This happens most often outside or inside on the ground floor, or at basement level. Negative water pressure caused by the level of the water table being higher than that of the tiled floor can also cause problems in basements.
Most cement-based tiling systems are affected by these salts; the damage caused is irreversible over the long term and will ultimately make the system fail. In addition to chemical attack, salts crystallising on the surface of porous elements will cause mechanical damage as they expand. All of this means that if there is no structural DPM, or there is evidence of salts on the surface of the screed, you must install a capillary barrier as the first element in the system.
The best way to do this, if space, costs and application time allow, is to lay an unbonded screed over an anti-capillary polymeric barrier, such as Aquastop Green. If that is not possible, then the next best way to prevent the problem occurring is to clean the substrate thoroughly and mechanically remove any salt crystals that have formed on the surface to stop them preventing the system bonding with the support.
Next determine whether the substrate is dry or wet.
On a dry substrate, apply Aquastop Nanoflex to waterproof the substrate. This single component product stops the passage of water and salts, but allows water evaporation to occur. This means that vapour pressure will not build up and possibly cause the floor to detach. You can install the tiles with an adhesive from the H40 range which has the best mechanical compatibility with Aquastop Nanoflex. Then grout with Fugabella Color as this can be used inside and out, and also allows water vapour to escape.
On a substrate with high humidity, use Metric Osmotic, which is an osmotic waterproofing agent, which blocks the surface pores of the concrete substrate and withstands the salts present in the rising damp.
Finally, in basements where the floor is lower than the water table, you need to get a competent technician to assess the structural stability of the slab. They will make sure that if it is waterproofed, it will still be able to stand up to the tensions generated by the water pressure and meet the British standard.
Flood-prone areas
One of the questions we frequently get asked is about breathable systems that will dry out quickly if flooded. We recommend adding Aquastop Green, a multi-layer anti-fracture polymeric membrane, to the previous system. This helps eliminates water vapour through its internal channels and absorbs any sideways movements that occur, which will safeguard the tiling installation.
Need more help?
Please don’t hesitate to get in touch with our technical team who can answer your questions and provide advice on your situation.
Email: [email protected]
Phone: 01772 456 831