Modified vs unmodified thinset

[tomthetoolman40]

What is the difference? Are they for different applications?
Tom

[David Meiland]

That's a big topic. I suppose to cover the basics you can say that modified is stickier and stronger, and it's what you want to use with porcelain tile.

[tomthetoolman40]

Ok, but my thought is then why do they manufacture unmodified? Are there applications where modified would be unsuitable, and you would need to use unmodified?
Tom

[always-learning]

Unmodified is used in applications where there is the inability for the moisture to evaporate through the either the substrate or the tile above.

For example....where tile is installed over Ditra. The thinset is sandwiched between the ditra (plastic) and tile and has little surface area for the moisture to escape and allow for curing, so an unmodified thinset is used because it will cure with minimal or no availability for the moisture to evaporate.

This is what the representative from schluter explained to me at a show a few years back.

Look at this diagram on page 12

http://www.schluter.com/media/DitraH...9-2007-ENG.pdf

[shawn23]

Sometimes it is just the expense. Why spend money on polymers which are not needed.
When you are installing over concrete that is sound you do not need modified mortar as it will stick just fine and will not be subjected to flexing, but on plywood floors where movement is likely it is best to use a high grade thinset with lots of admix.

[Nickymg]

If you read discoloration in light grout you will learn from our mistake that unmodified thinset is suitable and unmodified not suitable for when using the Kerdi/Schluter system.

Nicole

[Kgphoto]

If you read discoloration in light grout you will learn from our mistake that unmodified thinset is suitable and unmodified not suitable for when using the Kerdi/Schluter system.

Nicole

I read this twice and can't understand it. Is there a typo or am I just tired?

[Nickymg]

I think I am tired - it does not make any sense at all! Sorry, do not worry about it. I am not tile expert.
Nicole

[mbyrne]

Dry-set thinset mortar has no polymers and is basically sand, cement, and some retarder. It is the first thinset mortar developed (no, it was not engineered specifically for Schluter products). You can add a liquid latex or acrylic in place of water to make a modified thinset. Dry-set thinset mortar will not stick to wood after curing.

[scuttlebuttrp]

Are you sure about those facts Mr. Byrne? I thought Herr Schluter invented unmodified after creating the Internet with Mr. Gore? :)

[user843839]

Dry-set thinset mortar will not stick to wood after curing.

Mike, could you explain this a bit more. I don't understand what you mean by "dry-set thinset mortar". But since I'm just a GC, not a tile setter, I think you will understand. Thank you.

Regards,

Tom

[Kgphoto]

Thinset morter, when "dry" will no longer adhere to plywood. That is why modified was created.

[scuttlebuttrp]

Dryset mortar and unmodified is the same thing.

[user843839]

Dryset mortar and unmodified is the same thing.

Thank you! Now I understand.

Tom

[dgbldr]

Unmodified is used in applications where there is the inability for the moisture to evaporate through the either the substrate or the tile above.

For example....where tile is installed over Ditra. The thinset is sandwiched between the ditra (plastic) and tile and has little surface area for the moisture to escape and allow for curing, so an unmodified thinset is used because it will cure with minimal or no availability for the moisture to evaporate.

This is what the representative from schluter explained to me at a show a few years back.

That's a good-sounding theory but it doesn't hold any water (pun intended).

Custom guarantees modified over Redgard. Actually they require it. From Redgard data sheet:
TILE INSTALLATION
Install tile or stone with a Custom® polymer-modified mortar meeting ANSI A118.4 or A118.11 standards.

Schluter must know something we don't. Or they may be relying on technical advice from Mr. Gore :)

dg