I'm not familiar with that brand.

Under the mixing directions it should give you the recommended amount of either water or acrylic admixture.

If it says to only use water, then the additives are in a powdered state and become activated by moisture.

I'm not a fan of the water mixed products.

IMO, Mapei Kerabond/Keralastic system is the absolute top of the line product. I've been using Hydroment lately, however.

I offer the lifetime guarantee on my work, though. ;)


KT

The M-Bond Pro calls for just water

The "brown wrapper" Thinset Mortar 911 says that water is acceptable, but suggests a product called CureCryllic Premium. The stated mixing rate is "approximately 1.5 gals/50 Lb bag.

PRODUCT DESCRIPTION
CURECRYLIC® 939 Premium Admixture is an
acrylic latex emulsion that has been
specifically formulated for addition to C-Cure
dry-set mortars to provide a bond coat for all
types of tile over a variety of substrates
including exterior grade plywood (EGP).
CURECRYLIC PREMIUM 939 will provide improved
bond strengths, freeze-thaw stability and
increased flexural strength over normal
dry-set mortars.
BASIC USE
CURECRYLIC PREMIUM 939 is primarily used as a
dry-set mortar additive in lieu of water to
produce a bond coat for setting absorptive,
semi-vitreous, vitreous and impervious tiles
for service in residential and commercial use.
It is suitable for interior and exterior use in
a mortar bed as thin as 3/32" to 3/16"
(2.4 to 5 mm) after tiles have been properly
embedded. CURECRYLIC PREMIUM 939 modified
dry-sets have excellent impact resistance, are
water cleanable, non-flammable, and greatly
reduce water absorption which weakens
normal bonding material when subjected to
freezing conditions. CURECRYLIC PREMIUM 939
modified dry set mortars are not affected by
prolonged contact with water after curing but
do not form a waterproof barrier.

Randy

Soooooo? How's it going?

Are you done yet? :D


KT

HAH! Not even close to being close...

All I've done since the last post was to lay out as many full pieces of backer board as i could. No cutting of it yet.

Once I had all the pieces laid out, I traced them onto the floor, as I removed them, one by one. I now have my pattern laid out and know how the full pieces will fit as I'm setting them in place.

Unfortunately, I probably won't get to actually putting them in place until Sunday. :(

Randy

Well, after being pulled away from this job to work on other things, I was finally able to get a little work accomplished this past weekend. I now have a big chunk of the backerboard laid into place. Also had to disassemble the bathroom sink and toilet and remove the closet flange. I'll install thet back once the tile is in plcae so I can get it installed sugly against the tile.

A few days after laying some of the backerboard, I was walking gingerly acrossed it and noticed a little gritty feeling underneath it in a couple of small areas. It seems as though the thinset underneath it is broken up a little bit and not providing much (if any) adhesion in these areas.

There are 2 or 3 areas about a foot in diameter that are like this. I wouldn't be worried about them if they were located underneath where the couch or the refrigerator are going to be, but these are right in the middle of the pathway leading to the garage door.

Should I pull these pieces of backerboard up and reset them (or new pieces), or can I just disregard them. My thoughts are that the gritting will just get worse, but I'm always open to new isdeas.

Randy

You could drill some small, maybe 1/8-1/4" or less, holes in each area you think are problems, and use a 10-20cc syringe to shoot some thinset into the space. That's what I'd do. You want a "slip-tip" style syringe.

Hmmmm, not a bad idea, Pat. Definitely worth considering.

I did some searching around on the John Bridge forum and there seems to be a consensus that the thinset isn't there to actually adhere the backerboard to the plywood, but rather to simply fill in the gaps and remove air pockets.

A few of the regulars there actually suggested setting a few more nails in the "gritty" areas, since the job of the jails (or screws) is to actually do the fastening of the backerboard.

Injecting some thinset would probably fill in the pockets, but perhaps fastening the floor a little more just might do the trick.

Gonna have to ponder this a bit.

Randy

I'm actually surprised you have any give in the backerboard, particularly with the flood of fasteners used. Get some screws and go to town.

I wouldn't say the backerboard actually has any "give". I mean, there are 54 screws in each full sheet, so they're definitely fastened down.

It's actually the gritty "sound" that bothers me. I can certainly run a lot more screws into it, that's no problem at all with the gun. Would only take a matter of seconds. But I'm afraid the "gritty-ness" will still be there.

Bottom line is, if it has to come up, I'd rather do it now, rather than once it's covered with slate and grout. :(

Randy

http://forums.pelicanparts.com/uploa...1170303234.jpg

That "gritty" sound is going to persist after you install the tile. Was there anything on the wood subfloor there that might have fought the thinset? Perhaps there was a dip in the floor there and the CBU did not fully seat into the thinset? The problem with the drill/syringe fix is that you might end up with a high spot in your floor if you're not careful.

I'd hate to call it good and install tile only to develop flex later - but I can't picture that with a screw down job over mortar...

88 nails per sheet...( 3x5 )

Sounds like you are not using a 1/4 x 1/4 notched trowel or your thinset is too stiff.

Are you sure you are not hearing the subfloor moving?


KT

88 nails per sheet. I just went back and looked cuz I know you posted a number earlier...and wouldn't ya just know it...that's exactly what you said a couple of weeks ago! :D The question now is this: Any problem with hitting the sheets I've got laid down with more nails?

For the trowel, it is indeed a 1/4 x 1/4 notched trowel. It's the same one I used on a previous, but much smaller tile job.

When you say the thinset may be too "stiff", do you mean it's already begun to set up, or that it was mixed to thick?

I really don't think it was the latter. In fact, following the directions on the bag, it called for 2 gals of water for a 50# bag. After mixing it with my drill moter and mixing bit, the stuff actually seemed thin. It wasn't as thick as creamy peanut butter or a Wendy's Frosty, as I've heard recommended. :D

I let it stand for a good 15 minutes to set up and then mixed it again. It still seemed somewhat thin. Thin enough to where I ended up scooping the stuff out with a plastic bowl because the trowel didn't seem to hold very much of it.

Finally, I am pretty sure it's not the subfloor moving that I'm hearing, but if it is, would more nails in this area resolve this?

Randy

For backer I like the thinset to be a pourable consistancy.

"You can't over-nail a subfloor"...


Nail the area in question.

KT

Also, any possibilty you are sinking the nails too deep? do you have the regulator on the compressor at around 115 PSI?.

I prefer to "chase" the high nails after each sheet is in, rather than setting a ridiculous number of hand nails.

Over-nail the corners. Sink a hand nail in the intersections.


KT

"Pourable"....that sounds about right. It wasn't really watery, but it wasn't really thick, either. "Pourable" describes it pretty well.

I'll hit it with some more nails then. ALL the boards.

Thanks!!!

Randy

Nahh, the regulator was set to 90 psi. After reading your earlier posts on nailing, I figured I would rather follow behind with a hammer and sink whatever ones didn't seat, rather than double or triple nailing the "over-sunk" nails.

Great idea, btw, hand nailing the intersections. I'll do that too. :D

Randy

You know, we are going to need some pictures along the way here? :D


KT

Yeah, and an audio recording of the "gritty sound" would help as well.:cool:

Did you vacum and/or sweap the floor b4 going in with the thinset? Maybe that area had some dust you missed and the mortor didn't grab? Pictures are mandatory now...:)