help on ad-mixes

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Old 04-05-06, 05:56 PM
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help on ad-mixes

Hello-

I have a kitchen floor I am getting ready to tile - italian made 13x13 tile - the subfloor is plywood with hardibacker board on it. My question revolves around the thin set and grout I am using and any ad-mixes.

First - I'm using Laticrete - Lowe's brand essentially. I have the modified thin set (253) bagged mortar - my assumption is that I can use pure water with no ad mix since this has the powder additive already. And this will provide me adequate flexibility to prevent any cracking.

As for the grout - it is the Laticrete series 1500 - the bag says it too has a polymer added - so can I use straight water here also?

I bought 2 ad-mixes: Admix plus 1776 with an antimicrobial and the Super Flex additive 333. My take is that the 333 is made to add to plain thin set - but isn't necessary for the 253 I got. Is there any benefit from using extra polymer by using this "milk" anyway? Should I use it in the grout to get additional flex? And as for the 1776 with antimicrobial - should I even use this at all? Doesn't look like it provides a benefit for flex.

Anyway, these are the materials I have and I am just trying to determine which and in what mixes I should use them for best results.

Thanks in advance!!
 
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Old 04-05-06, 10:28 PM
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253 thinset, just use water. Mixing with admixes prevents the proper hyrdation of both the portland and powdered polymer components of the thinset. Using admix actually reduces the performance of bagged polymer modified thinsets.

1500 grout, if you have well water or a water softener -or- you will be grouting over more than one day, the admix will help with color uniformity. Otherwise, just use tap.

Which laticrete product did you use under the hardibacker?
 
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Old 04-06-06, 05:16 AM
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Great advice on the ad-mixes - Thanks!

As for under the hardibacker - I used no thin set of any kind - There was a 5/8" subfloor - I added 3/4" ply and hardbiacker on top of this. Then I screwed the crap out of those things - the hardibacker has spots for you to screw in to - I screwed in every one - probably 40 or so screws per 3x5 sheet - I have never used anything other than this setup and it has worked well. Is using something under it typical? I have only heard of that for specific cases...

Again, thanks for the tips on the ad-mix for the thin set.
 
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Old 04-06-06, 07:18 AM
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As for under the hardibacker - I used no thin set of any kind
I expected that because you asked about admixes after you had the Hardi installed.

Is using something under it typical? I have only heard of that for specific cases...
Every horizontal application of cbu's, no matter the brand, require a bedding layer of thinset underneath. They are all non structural and provide only a bonding surface. They need the thinset underneath to fill all the voids that exist between the ply and the backer. Any unmodified thinset is great for that purpose. In your case, Laticrete 317 as it will be right there along with what you bought, but any bag that says"Conforms to ANSI A118.1" will work.

Not using thinset under the backer becomes a question of WHEN the floor will experience signs of failure, not IF. The time frame will depend upon factors such as area of use. A kitchen countertop, a bath floor, etc, you might get quite a few years out of it, of course, you might not. A kitchen floor is one of the highest trafficed areas in a house so an install such as yours will have a much shorter life.

The only situation where dry laying hardi is acceptable is when used as an underlayment for a vinyl floor.
 
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