Ardex 8+9

[mark999]

Can the seams and corners of durock be treated with durok tape and ardex 8+9 rather than thinsrt and tape? This is for a tub hop.The ardex pdf was not exactly clear on this.

Thanks

[CaliGrown]

Yes, just use fabric in your seams and changes of plane in place of the mesh tape. Your first mix is real thick like thinset on the dry side to fill in the seams and penetrations, then your next mixes are looser to embed the fabric and roll out the material for wterproofing. 8+9 is similar to thoroseal if that’s any consolation to you

[cx]

Mark, the 8+9 is a crack isolation and waterproofing product.


The Durock installation instructions, as with all CBUs with which I'm familiar, call for the seams to be treated with thinset mortar (or the product used to bond the tiles) and alkali resistant tape.

Two completely different and separate operations to my thinking.
The only time I know you can do what you're suggesting is when using a sheet-type waterproofing or crack isolation membrane that is installed using thinset mortar.

Not sure where Chris is getting his information on using the liquid-applied waterproofing as a substitute for the bonding mortar, but perhaps he'll tell us.

[CaliGrown]

http://www.ardexamericas.com/en-us/D..._8+9_5Step.pdf

Step 3

[cx]

Problem I see there, Chris, is that's the same instructions you'll find for RedGard and similar crack isolation membranes for treatment of cracks and joints. Satisfies the makers of the membrane, but I'm not so sure it satisfies the makers of the CBU panels.

[eurob]

Chris,
You are in the shallow end ........ Here it matters only what the manufacturer of the said product is recommending, without deviation from it.

However , if 8+9 allows it , for me is also good ....... With a cementitious waterproofing membrane .

[mark999]

Thanks for the reponses. I called ardex this morning and talked to tech support. Then I got my reps # and talked to him. Both said it was good to to use ardex 8+9 with their fabric to seal ceement board joints ,corners and change of plane. The rep said he thought it was better than ceement tape and thinset. They also said they would put it in writing if I wanted.

Went ahead and used it. It was a little learning curve but it worked quite well.Really sticky stuff. Started out with small batches. Stuff tends to thicken fairly quick.

Comes in grey and white. Wish the contractor had got white. Price wise it is close to the other paint ons. I think I prefer it to the other paint ons.

[Tiger Mountain Tile Inc]

I don't have any hands-on experience with 8+9 outside of a product workshop but I would feel comfortable using 8+9 for this application where I wouldn't with its liquid competitors.

But the by-the-book "safe" way of doing it is to fulfill the cement board manufacturer's requirements of thinset+mesh tape then waterproofing.

Does this mean that you are waterproofing the entire tub with 8+9? or just the corners/seams?

[mark999]

Thanks Jim,

Yes I did the whole shower (tub hop). Their written instructions give a fraction for the thickness(1/16? cant remember) so when I asked the rep about a film thickness gauge he said it was not nessasary and to apply 2 coats perpendicular to each other. When mixed to their paint on consistency it was quite thick but not too thick. It brushed and rolled fine and gave a nice solid coat.It dried fast and second coat made it look really solid. It is kinda like paint with very fine sand finish. Much easier to get coverage vs. the other liquids which are very hard to get thick enough.

The other thing I noticed was after it cured it was really durable. More like a skim coat of thinset vs. a rubbery film that can tear or peel off. Per coverage it is more or less the same cost as the others.

If I remember I will call USG tomorrow and see what they say. It is tech. not thinset but it is a cememtis type product.