How do I waterproof concrete, asphalt or existing tiles?
Before waterproofing, the substrate should be sound, clean and dry, with no dust, oil or grease. The rubber-based liquid waterproofing WARCO ALLESDICHT can then be applied. The type and condition of the substrate determine any additional preparation. Cracks and joints wider than 3 mm should be sealed beforehand. Movement joints should not be filled and are instead bridged with joint sealing tape.
Concrete, screed and asphalt should first be cleared of loose or friable areas. Spalled areas and deeper defects should be repaired and levelled. Fine cracks are filled by the viscous waterproofing compound during application. Porous or highly absorbent surfaces require a suitable penetrating primer, while dense substrates do not need priming. On asphalt, roofing felt and bitumen membranes, blisters, open seams and trapped moisture should be dealt with before waterproofing.
An existing tiled finish can remain in place if the tiles are firmly bonded. Hollow-sounding or loose tiles should be removed and the resulting areas levelled. Cracked tiles and open grout joints should be sealed. Waterproofing may be applied over a painted surface only if the coating remains firmly bonded to the substrate. Chalky, peeling or flaking coatings should be removed. Latex paint is not suitable as a bonding surface.
On balconies and terraces, the fall towards the outlet must already be correct before waterproofing begins. A fall of one to two per cent is commonly used. The coating follows the existing surface profile and does not correct an inadequate fall. At wall junctions, a cove is formed to allow the waterproofing to continue up the wall and be reinforced with fabric. Details around door thresholds, balustrade posts and outlets depend on the available upstand height and the drainage arrangement. At an exposed edge, a trim with a drip edge helps water to discharge clear of the structure.
Roofs finished with roofing felt, bitumen membranes or sheet metal may be refurbished if the existing covering is dry, sound and free from blisters and open seams. For plastic roof membranes, adhesion to the specific membrane type should be checked first. Roof outlets, rooflights, perimeter details, pipes and cable penetrations require additional fabric reinforcement. Localised damage may be repaired in the affected areas. If the roof covering is extensively aged or moisture has entered the roof build-up, the complete construction should be assessed before work begins.