The most waterproof type of sealant?

[Element]

I was recently asked to remove & replace the Silicon sealant around a shower tray. When I got to the job I found that apparently it had been leaking through to the ceiling below. Not surprising I thought when I saw the cracks in the floor of the (big) tray. I pointed out that there's no real solution other than to replace the whole tray and probably strengthen the floor beneath it. The client acknowledged this but can't afford the cost of such a major work at the moment so just wants to patch over as best as possible (I pulled out a lot of sealant from the tray floor thus revealing the pretty serious cracks).
So I did the best I could to make it look a lot better and sealed it all up as best as could be done with Mapei Silicon. I've just had a call and the client is asking me to return and add more Silicon or something else as it seems to be leaking worse now.
So the question is - what is the most waterproofing sealant I could use on a cracked, white floor of a shower tray? Is there something else such as maybe a rubberised, oil based roofing / gutter sealant. I know it'll not be perfect, I suspect it'll leak again but I think that there is probably something better than standard Silicon sealant...

Many thanks for your advice!

 

[WetSaw]

Polyester resin and over the whole thing?

 

[Ajax123]

Are you sure the leak is from the gap?? and not from somewhere else.

 

[WetSaw]

I'd also be a bit worried about the structural integrity of the floor if it's been leaking that long. Could the cracks be caused by the floor failing?

 

[Bert]

You may be opening a can of worms here, although you have pointed out the pitfalls of patching the job, when it re-leaks in the future you will surely be the first person they blame and expect to rectify an already dodgy job.

Regards.

 

[Element]

Polyester resin and over the whole thing?

That sounds feasible but I suspect it might just crack as I think the tray is flexing due to insufficient floor support - looks like the original job was dodgy IMO.

No idea where the leak comes from; can't inspect anywhere as its all covered and sealed in.

The cracks are most likely caused by the floor failing, the floor integrity is prime suspect.

I've emphasized that a patch job is not going to last and they acknowledge that; it was leaking before I replaced the sealant. It's an oversized shower floor tray, looks like its custom made / fitted - maybe 4' x 4' 6". Don't know how long its been leaking but I suspect years...

They want me to just use 3-4 x the sealant quantity (like it was before I removed it) over the cracks and around the sides. I'll suggest that if that doesn't last sufficiently long then polyester resin might be the next plan; at least that could vastly improve the tray floor weakness...

 

[WetSaw]

Could always put a layer or 2 of fibreglass in to make it stronger. Just make sure you have a good layer of resin on top so it's smooth.

 

[Stef]

I would go & buy an Ardex tanking kit & blitz the whole area with it & tell them that's the last repair you do on it..

 

[Element]

I would go & buy an Ardex tanking kit & blitz the whole area with it & tell them that's the last repair you do on it..

Just had a look at that - which led me to this :
[h=1]http://www.tilecouture.co.uk/product/ardex-s7-flexible-waterproof-coating/[/h]
It's designed for swimming pools and says its flexible.. I'm trying to get the detail difference between the two...

 

[Element]

I've decided to recommend they find a fiberglass specialist who could probably fit a new fiberglass / resin suface with a gel coat on top; this would stop any further leaks & not mean they have to remove and repair and replace - which would be far more costly. They're off my back now!

 

[Diamond Pool Finishers]

This would be great in this situation and the fact that that we use it on swimming pools would be a clincher in your customers minds .......