Advice on 'bad advice"

[F16fixer]

Hello, first time poster, and Im questioning some advice I got from another DIY friend.
Im laying a 18x18 granite tile, Ive checked my sub floor req. with that of the specs I found on this and other building sites. Im not using a detra layer, top most layer is hardi backer.
Issue I am having is I was given the advice to tape and thinset the joints of the backer board which I did. My sub was level, but the thinset on the backer has now created small deviations to that level in some areas where I will have a tile edge. (I prelaid all my tiles and saw all this) Also there is some rocking in tiles where the hardibacker seamed (caused by tape and thinset)

I thought I spread evenly (as I would with drywall mud), to me this seems like I took bad advice, (although the hardibacker website also suggested it) or I am missing a step.
Im wondering if this much of a deviation will affect my tile once laid since I will be using a 1/2 x 1/2 notch trowel (considering how large the tiles are) or if I am over thinking this.
Also, if anyone is of the opinion that this is problematic would you please suggest a fix to this, should I scrape it or buy a leveling product.
Thanks in advance
Will

[Diesel1]

I'm sure the pros will weigh in, but you are supposed to tape and thinset the joints. When I did my floor, I taped and shoved the thinset as deep into the space as possible and then ran the knife at almost a 90 degree angle directly over the joint. The joint is as even as the rest of the boards pretty much.

If you have any pictures, post them up and the pros here will gladly give their POV on it.

[K_Tile]

Flat troweling the tape with thinset is correct. This should leave min amount of material to cover the tape (1/16" +/-). Using a 1/2 trowel will wont be a problem

[jadnashua]

To make life easiest for you, you could have layed the tape while laying the tile. It's not like a drywall seam where it has to look pretty before the finish layer. Now, if they aren't flat, you can get yourself a rubbing stone, and essentially, sand it flat. If you go through the mesh tape, just lay a new piece on while spreading thinset to lay the tile.

You do have two layers of subfloor before you added the Hardibacker? Did you check the deflection in the room, too? All necessary for natural stone to survive.

[Houston Remodeler]

What Jim said (all of it esp the plywood part) plus;

You'll need such large trowel and some backbuttering for those large tiles the sppedbumps won't matter.

[dhagin]

What they said.

If you have more taping to do, it reduces the build-up if you mud & tape the seams as you tile. You need to tape before spreading the mortar, then when you spread mortar for the tile, just smoosh some mortar down through the tape with the flat side of the notched trowel.

[Levi the Tile Guy]

I generally tape before I set tile, but like Paul said with 18x18 granite you will be using a 1/2" trowel and medium bed mortar and there is no way that the minor bumps from the tape are going to make one bit of difference. You are going to have at least 1/8" of mud, prolly more like 3/16" - 3/8".

[F16fixer]

Thanks everyone for the responses. I guess I was just over thinking the problem a little too much for my own good. However, I think the next time I use the hardibacker I will be laying the tape with the tile as some suggested, which I think makes more sense. I dug as deep as I could into the "large granite tile" encyclopedia, even deflection which I had never heard of before was good, almost 0 movement. Besides replacing the sub there is a steel I beam that also supports directly below the tile site.

The "speed bumps" were not a problem at all with the 1/2 by 1/2 trowel, I definitely wasn't thinking of the smush effect on tile height and level with such a high rake on the thinset, being too concerned with how "un-level" and rocking are such a high concern with so large a tile. The only issue I ever ran into was in one of the speed bumps, where two tile met and I had to more thinset push through the grout line than in all the level areas.

Thanks again everyone,
Will

[Chugiak]

Will,

For those of us that haven't played with granite tiles before, could you post a few pics? Thanks!