Waterproofing over tiles?...

[Batpig]

Dear Sirs,

This topic may sound familiar, but I couldn’t find any threads specifically relating to it. My Bathroom is on a suspended concrete floor, and the ceiling below has been formed by "wet-plastering" the underside of the said concrete slab. The part of the ceiling directly below the Floor Waste pipe in the Bathroom is showing signs of water damage, with general discolouration and slight lumpiness over a small area of just a couple of square feet.

The problem is most likely being caused by a small crack in the slab that has probably been induced by the casting-in of the Floor Waste inside the slab during the original concrete pour. I can’t see a crack from above - because of the Bathroom floor tiles - but I’ve picked away at a small section of the damaged plaster ceiling below, and I’m pretty sure that I can see a bit of a crack in the exposed underside of the concrete slab in at least one area.

If possible, I don’t want to lift the Bathroom tiles to waterproof directly onto the slab or tile bedding in the more conventional way. I am therefore wondering whether there is a truly effective product for waterproofing the surface of the existing tiling - grout and all - that will wear well, and won’t make the tiles unduly slippery underfoot. I don’t know a heck of a lot about "Tile Sealers", but something better than the usual run-of-the-mill might be warranted in this situation.

I am also wondering about the best preparation to get the tiles "squeeky" clean before applying the sought-for waterproofing product.

Recommendations of any decent Brisbane-based Waterproofing contractors who you think might offer a good solution would also be welcome, because I want to get the shower-recess professionally waterproofed before any new tiling goes on in there anyway.

Many Thanks,
Batpig.

[journeyman Mick]

.............I am therefore wondering whether there is a truly effective product for waterproofing the surface of the existing tiling..............

There isn't. There a re a few products that can be applied over the tiles and grout but they will leak over time - how much time is anyone's guess.

Mick

[bricks]

Product is called shower seal and comes with ten year warranty if applied by a plumber or builder with a liscence, available at Reece or similar plumbing stores cost about $100 for the product.

[billbeee]

If you can see a distinct crack underneath you could try epoxy injection. Probably not applicable for your job, but I have never seen anything you can add to the surface of a bathroom floor that will do a permanent job.

We used to use Epirez hydrophillic epoxy, (water compatible).
The technique is easy and cheapish compared to any other way of doing it.
Grind a vee in the crack, bed in standard grease nipples at say 200 centers with epoxy mortar, filling the crack as you go. A couple of days later you pump a thin epoxy into the nipples with a grease gun.

Start with just one nipple tight and the other loose, and as the epoxy reaches the next one, tighten it and pump from that one and so on.

A day later grind off grease nipples.

Cheers
Bill

[silentC]

How old is the house? Are you sure you don't have a case of concrete spalling there? If you have a crack in the floor and there is moisture coming through, I think I'd be pulling up the tiles to check what's going on underneath. Spalling happens when moisture gets to the reo causing it to rust and it expands cracking the concrete.

[Batpig]

No, definitely not spalling SilentC. The concrete is quite sound above the plaster where the lumpiness is at it's worst.

Billbee - epoxy injection from below sounds interesting, but could be overkill. Will have a closer look at the pattern of the cracking to see if it is suitable for your proposed method when I get a chance to get all of the affected plaster off the underside of the slab.

Bricks - Shower Seal sounds good. Could perhaps apply it to the tiles above, leave the plaster below alone for a while to let things dry out a bit, and then re-plaster down the track. Plumber will be coming out soon to put a new combination in the wall of the shower recess, so I'll talk to him about the possibility of bad joins, etc, in the PVC before I do anything else. You wouldn't perhaps know who manufactures the Shower Seal would you? There are a couple of outfits called Shower Seal that come up when you do a Google, but they appear to be more along the lines of Waterproofing contractors...

Thanks to all,
Batpig.