Any professional tilesetters in here - Ditra Mortar Coverge

[chefwong]

How accurate is this per their handbook:


To bond DITRA to the substrate: Use one 50-lb. (22.68 kg) bag of mortar per 150 - 200 sq ft (13.9 - 18.6 sq m).
To bond the tile to the DITRA: Using a 1/4" x 3/8" (6 mm x 10 mm) square- or U-notched trowel will require 50-lb (22.68 kg) bag of mortar per 40 - 50 sq ft (3.7 - 4.6 sq m)


I'm ~traveling~ to pick up Kerabond and having extra bags (returns) is not exactly a option with the supplier.
I'd like to be on target for real world usage on the amount of mortar used for Ditra (application, waffle filling, tile)

[jadnashua]

The bonding to the substrate is fairly consistent. Note that the type of thinset you use depends on what the subflooring is: if it's a wooden subfloor, it must be a modified thinset, otherwise, it can be an unmodified...they are quite specific in their installation manual and it behooves you to follow it for best results.

The top, setting tile, is more problematic. The more irregular the subfloor or inconsistencies in the tile will call for more thinset to ensure that you get a nice flat tile installation. And, they specify this thinset must be an unmodified variety. So, you may need two different varieties, or an unmodified with an approved, add-in modifier, or separate varieties.

How fast you work, and how much wastage you have from maybe not using all of the thinset prior to it starting to set up may also have an effect on your coverage. Also, how you hold the trowel can make a big difference in the actual thickness of the applied thinset. Hold it at 90-degrees will use more than holding it at say 45-degrees. So, estimates are just that.

In the scheme of things, the stuff isn't all that expensive...depending on what your time is worth, having an extra bag or two probably shouldn't be a deal breaker. Also note, the stuff you buy will have a manufacturing date code on it, or a use by date. It does potentially go bad - you don't want it to be close to the use by date when you just get it - fresher is definately better. If the bag isn't sealed perfectly, or it has a small hole, or it is improperly stored can all impact the stuff...portland cement just loves to absorb moisture, and if it does, it may not make the bag a solid, but it may end up being a lot of cured 'sandy' particles, that won't adhere to anything.

The guys over at www.johnbridge.com use a lot of Ditra, you might ask there.

[chefwong]

No offense to the moderator over there.....but they have a guideline on questions being posted on a *continuous* project thread and sometimes questions don't really get responded just due to the original thread questions / title ----- whereas I may even break the rule and post a good title respective to the question being asked, only to have the thread moved into the *project thread* or what I call the blackhole...

Concrete is the base. The goal is to screed flat (not level but flat) and then Kerabond/Ditra/Kerabond/Tile.
Methinks it will be 2 phases - mainly due to tile still being on the boat....and phase 1 will just be flat, kerabond, ditra and fill in the waffles.

[chefwong]

Some more questions if any tile pros may come upon this thread


Mapiceme
Anyone use this. I have used their Planipatch eons ago and hated it.
What I like about Mapiceme is that it's rapid set....and can go down to 4".
Even laticrete most competing product is 1/2".
And the latter I was looking at, Sakrete B1, their set time was not as fast as Mapiceme but decent at 2" fill level as well.


-http://www.mapei.com/US-EN/product-d...89&IDLinea=103

[chefwong]

Last but not least

THE GREAT DEBATE
Modified vs. Unmodified WITH DITRA

For example, I used Lat 254 and may have even used it as thick as 1 1/4" inch - porcelin tile over concrete. I have had drills drop ontop as high as 6 feet....at least 4 times since I have it installed and no damage to the tile whatsover

I'd be inclined to set the Ditra and fill in in the waffles with modified...
Bearing I'm not laying tile ontop for another 2 weeks, I would think that the modified bed might be stronger than non.
Warranty or not....

[BobL43]

No offense to the moderator over there.....but they have a guideline on questions being posted on a *continuous* project thread and sometimes questions don't really get responded just due to the original thread questions / title ----- whereas I may even break the rule and post a good title respective to the question being asked, only to have the thread moved into the *project thread* or what I call the blackhole...

Concrete is the base. The goal is to screed flat (not level but flat) and then Kerabond/Ditra/Kerabond/Tile.
Methinks it will be 2 phases - mainly due to tile still being on the boat....and phase 1 will just be flat, kerabond, ditra and fill in the waffles.

My personal experience with the John Bridge web site has been great. all my questions I keep in my project name thread, and If I have new question to ask relating to my project, I just enter a title in the title box up at the top of my reply. Has worked great so far. Everything I asked has been answered for me by the pros.

[jadnashua]

You need to understand the chemistry of modified verses unmodified...a modified mortar has components that must dry to achieve the system's full strength. It must outgas water vapor for this to occur. Essentially, a modified is a layer of a laytex type material that encompasses a matrix of cement. The laytex provides a protective barrier around the cement and is stickier. Until the laytex dries, it is easy to tear the bond. Think rubber band verses a concrete block.

Ditra is essentially waterproof. Porcelain tile is essentially waterproof. The drying can only occur via the grout line gap, and if you decide to fill it with grout before that happens, it can literally take months to achieve its strength (concrete based products strength is based on curing for 28-days - an unmodified achieves more sooner when placed between two waterproof surfaces like Ditra and porcelain). While, eventually, this will happen, if you walk on or move heavy object over the floor, you may crack a tile or break the bond. Because the manufacturer has no control over that, and few installations would restrict access for that long, they tell you to use a (good) unmodified. They will give you an approval to use a rapid set modified, but that is not something a typical DIY'er should ever consider. A rapid set modified will achieve enough strength to prevent most disasters, but will still take forever to achieve the stated full strength. IOW, a good unmodified may provide equal strength, but not quite as fast. The rapid set would allow a pro to potentially set and grout in the same day.

An unmodified thinset only needs to cure...if there were excess moisture (within reason), it would not affect the curing time or the strength (too much moisture, and you will compromise the strength, though). This is predictable. So, while a modified may have a higher ultimate shear strength, that difference would be lost if you didn't allow things to cure AND dry properly, and it means an extended 'keep off' time.

A good unmodified thinset (not the entry level, cheap price leader which is mostly sand!) will typically have a shear strength of 300+ pounds/sqin. A good modified may increase that by a third. But, take a typical 12" sq tile 12*12*300=43,200 pounds! Are you really expecting to need more than that? The Ditra would debond long, long before the tile would break off the mortar.

Compressive strength is in the same ballpark, and if you had a point load big enough to be an issue, you'd crack the tile first anyway with either.

If you want to fill the waffles first and can let it sit for a couple of days, you could use modified for that. But, I'd still use unmodified to set the tiles on it. I've dumped a clump of modified out on newspaper and let it sit for a few days prior to throwing it in the trash...in the center, it was still soft and springy. That doesn't happen with an unmodified as it will cure anaerobically.

Any manufacturer (with any kind of integrity) spends a lot of time prior to making recommendations on how to use their product...do you really feel you have enough info to second guess them?

[johnfrwhipple]

Some more questions if any tile pros may come upon this thread


Mapiceme
Anyone use this. I have used their Planipatch eons ago and hated it.
What I like about Mapiceme is that it's rapid set....and can go down to 4".
Even laticrete most competing product is 1/2".
And the latter I was looking at, Sakrete B1, their set time was not as fast as Mapiceme but decent at 2" fill level as well.


-http://www.mapei.com/US-EN/product-d...89&IDLinea=103

Mapecem Fast Setting Screed Mortar is my favourite product for shower construction. At 15-16 per bag that is a ton of technology in one 40 pound bag. Love love the stuff. 1/4" - 4" in small areas. 1/4"-2" in larger areas. You need the Admix for a slurry coat as well.

[johnfrwhipple]

Last but not least

THE GREAT DEBATE
Modified vs. Unmodified WITH DITRA

For example, I used Lat 254 and may have even used it as thick as 1 1/4" inch - porcelin tile over concrete. I have had drills drop ontop as high as 6 feet....at least 4 times since I have it installed and no damage to the tile whatsover

I'd be inclined to set the Ditra and fill in in the waffles with modified...
Bearing I'm not laying tile ontop for another 2 weeks, I would think that the modified bed might be stronger than non.
Warranty or not....

It is crazy to install Ditra and use modified thinset on top??? It's not allowed by Schluter and why void your warranty. Go pick up Spider Web from Custom or Dural online. Both embrace modified thin set and you do not void your warranty. That way as well you can use your premium thinsets.

You will love the mesh over top of these products. It is a positive mortar lock or so they say. I find it helps slice up the thinset when filling the waffles and the product is easier on the knees than ditra. With ditra it's hard to get your mortar filled in perfectly.




You are forcing a solid mass into a dish so air is trapped, much like drywalling and filling the screw heads. For some reason the mesh with the Spider Web makes this process a little easier.

[johnfrwhipple]

You need to understand the chemistry of modified verses unmodified...a modified mortar has components that must dry ...

Jim if you just dropped Schluter from your recommendation list you could have some much more free time. People do not want to understand the chemistry. People do want warranties.

To install Ditra over plywood you need two thinsets. On to install the ditra to the plywood and one to install the tile over top.

Most dry set mortars (which are rarely used) in off the wall locations are expired or over a year old.

At least when you push the amazing powers of dry set mortar remind people to check the date codes.

Since most people use modified thinsets most modified thins sets are fresh (ie under six months old).

So it is easier to buy a product and tile that accepts modified thin set.

If the installer wants "Crack Surpression" Ditra doesn't even do that. Noble Seal TS does and can be ordered online and shipped right to the door.

Jim you have been brain washed by the giant Marketing Machine that is Schluter Systems.

[jimbo]

I don't think the installer needs to UNDERSTAND the chemistry. jad apparently does, and his explanation tells us WHY we should FOLLOW the recommendations of the manufacturer when we decide to use their product. WE don't need to know the chemistry, just READ the instructions!

As to purchase of supplies, you can make your best estimate, but if you don't include a factor for waste...will you use every last ounce of mortar from every bucket you mix up???......then you will end up making a trip back for more. How much is that inconvenience worth, compared to the price of an unused bag?
I'm sure a professional tile contractor gets pretty good at their estimating, but I guess they usually have an extra bag of mortar on the truck just in case!

[johnfrwhipple]

...WE don't need to know the chemistry, just READ the instructions!...

Exactly

Mapecem Screed mortar gives 14.5 square feet coverage at 1/4" thick. Per 40 pound bag. These measurements are very accurate.

[chefwong]

Project is quite underways....

ended up using Mapecem
Ultraplan M20
Kerabond
and Lati 253 Rapdiset....

All good stuff......

[BobL43]

It is crazy to install Ditra and use modified thinset on top??? It's not allowed by Schluter and why void your warranty. Go pick up Spider Web from Custom or Dural online. Both embrace modified thin set and you do not void your warranty. That way as well you can use your premium thinsets.

You will love the mesh over top of these products. It is a positive mortar lock or so they say. I find it helps slice up the thinset when filling the waffles and the product is easier on the knees than ditra. With ditra it's hard to get your mortar filled in perfectly.




You are forcing a solid mass into a dish so air is trapped, much like drywalling and filling the screw heads. For some reason the mesh with the Spider Web makes this process a little easier.

Hi John,

I went onto Custom's website and saw all their info on the Spider web matting and mortar, but I see that the mat is sold only as 30 Sq meter (323 Sq ft) rolls. Is there anyplace to buy smaller quantities, as I only need about 50 Sq ft of the mat. I have not called Custom to find out yet, just thought I'd ask here first. I like the concept of being able to use just one type (modified) thinset.

Thanks,

Bob

[jadnashua]

Pretty much everyone that sells an unmodified, also sells the admix separately...one bag, dual usage, you can get modified when needed, or unmodified when not.

With any cement based product, shelf-life is an important issue...the quality of the store and turn-around all play a big component in what you get. Just a little moisture can turn a bag of mortar into cured sand particles over time...it may or may not have been enough to make it a solid blob, but it won't hold a tile properly. Never use an old bag, or one that has 'chunk's in it. You're risking things if you use an opened bag that has been sitting around for a bit unless you were REALLY careful about sealing it back up again, and never longer than the shelf-life date code.

Just like you shouldn't buy an outdated bottle of milk, that doesn't mean you may not find one on the shelf...it is just one of those things you, as a consumer should check.