Roger Bisby looks at Classi Seal.

For years I have been banging on about the need to produce an effective sealing system around baths and shower trays. As a plumber I have been called out to countless leaks, which have often resulted in major remedial works. I remember one job in particular where we had to replace floor joists and completely re-plaster and retile a bathroom, all because a shower tray had leaked around the edge. How, I asked, can we put a man on the moon but still not solve this simple problem?

Let’s be honest now. A square sided tray butted up against a not quite square corner is never going to be successful. Add building shrinkage and a bit of flexing of floorboards and tray and you have a gap. It might not be a big gap but, as every builder knows, there is only one thing that water likes more than a big gap and that is a small one. If you could watch capillary action under a microscope you would see that water draws water. Once it starts it always brings more along behind it. Add a pumped shower to this and you are on a hiding to nothing.
  
Silcone is useful but it isn’t the whole answer because it often loses adhesion, and breaks down under mould. The best solution that manufacturers have come up with is an upstand built into the tray, which is fine if you can set the tray in behind the tiles and still maintain the correct dimension for the shower screen.

Classi Seal is another remedy that achieves the same thing on baths and shower trays. It has been produced by Classic Marble, a leading manufacturer of quality shower trays and screens. The self-adhesive flexible upstand can be fitted to any shower, bath or worktop. The rubberised material will accommodate movement of up to 15mm between the shower and the wall.

All you need to do is stick the strip to the tray or bath edge and push the tray into the wall. The flexible upstand can then be tiled over. The backing is peeled off 100mm at a time to expose the butyl rubber seal to the edge of the tray. Be sure that the side of the tray is cleaned with steel wool to remove any surface sheen or contamination.

What I really like about this seal, as opposed to rigid upstands, is that the flexible rubber is thin enough to be accommodated in the tile adhesive bed. This avoids that nasty little kick which is so difficult to overcome, without chasing a solid upstand into the wall.

Using a strip like this is a belt and braces measure which should help avoid a lot of call backs and it is being taken up by housebuilders and plumbers who are keen to eliminate any possibility of leaks around trays and baths.

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