I have just had a "pavement-vault", i.e. an old coal-cellar leading off the lobby of my basement-flat, tanked with Sika-render.
The last coat was only applied about a week ago, though it is now hard , but since then we have had a couple of down-pours and I have been very worried about seeing large areas of the ceiling becoming beaded with large drops of water.
The builder tells me not to worry as it is not leaking, it is just water coming out of the drying render, which contained large quantities of water. I have to admit it does not look like a leak as the water is not entering in quantity in any one place, it is evenly spread in beads, like condensation. In fact, it occurs to me that it is condensation, which I have had a problem with in the lobby, as it is cold and next to the warm living-room, but it seems a huge amount.
I am beginning to wonder whether I have made a big mistake here, and should have gone for a more-expensive plastic-membrane tanking system. But it is hard to believe is hard to believe that this well-known and respected Sika-render could fail in this way in a few days and therefore that it could be rain-water penetrating. On the other hand it seems to me the problem has only occurred on the two rainy days we have had.
I feel very way about continuing with this project (doing the floor, installing electrics etc) until I am sure about the effectiveness of this tanking. Does anyone have experience of doing this kind of tanking and what the problem, if there is one, could be. I have currently put a portable dehumidifer in the room to see if that helps.
