Asked by: Engracio Alfaro-Troyas
home and garden indoor environmental quality

What happens if you use modified thinset on Kerdi?

Last Updated: 19th April, 2021

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Modified thinset mortars aren't recommended for use with Kerdi because they must dry out to gain strength, whereas the membrane inhibits drying, which can lead to unpredictable results. For example, if a shower is used before the mortar has cured properly, leaks and polymer leaching can occur.

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In respect to this, what Thinset do I use with Kerdi?

Unmodified thin-set mortar is recommended to set ceramic and stone tile, including large format tiles, over the KERDI membrane. Portland cement-based unmodified thin-set mortars are dependent on the presence of moisture for hydration in order to gain strength.

Also, should I use modified or unmodified thinset? It's important to note that latex-modified thinset can still be used between the membrane and the subfloor because it is not impervious. However, unmodified thinset should be used between the membrane and the tile.

Keeping this in consideration, what happens if you use modified thinset on Ditra?

The problem with using a modified thinset is that it takes forever to dry over Ditra, especially with porcelain tile, being that it has an impervious barrier above and below. Schluter has said that if you use a modified thinset to set the tile that you can have to wait as long as 7- 10 days JUST TO GROUT.

Is unmodified thinset waterproof?

All portland based cementious products will allow water to pass through. The latex modified is more resistant due to the latex that is mixed in with the adhesive but that doesn;t make it "waterproof". The latex also allows a bit more flex in the tile and substrate. As Jason described, thinset itself isn't waterproof.

Related Question Answers

Aqib Elzardui

Professional

What is the difference between unmodified and modified thinset?

Unmodified thinset has been around forever. Unlike unmodified mortar, which consists only of a blend of Portland cement, sand, and water retention agents, modified thinset includes additional retention products, such as latex polymers, which can increase its performance and strength.

Joachin Tunev

Professional

Can I use thinset over redguard?

You''ll be fine with thinset over Redguard on walls. It's recommended for waterproofing niches, shelves, and entire shower walls when tar paper or poly are not used as a vapor barrier behind the CBU.

Thi Essafi

Explainer

How long should Kerdi dry before tiling?

Wait 24 hours after the membrane (i.e., Schluter®-KERDI-BAND and Schluter®-KERDI) installation is complete to allow for the final set of the mortar and to ensure waterproof performance of the assembly at seams and connections before water testing.

Lijie Sei├žas

Explainer

Is VersaBond modified or unmodified?

VersaBond® Professional Thin-Set Mortar. A professional formula, all-purpose mortar, polymer-modified to provide good bond strength for floor and tile projects. VersaBond® cures quickly even in cold climates and adheres to most surfaces, exceeding ANSI A118.

Edwin Toboso

Explainer

What type of thinset do I use with Ditra?

For example, to set DITRA over plywood or OSB, a modified thin-set mortar meeting the requirements of ANSI A118. 11 is used. To set DITRA over concrete or gypsum, Schluter-Systems recommends an unmodified thin-set mortar meeting the requirements of ANSI A118. 1.

Mitkov Seehausen

Pundit

Is fortified Thinset the same as modified?

Latex modified usually refers to the multipurpose thin-sets that are 118.4 compliant that are mixed only with water. A latex fortified thin-set is a dry set (118.1) that is fortified with an additive (such as 317 mixed with 333 super flexible additive) that makes it 118.4 compliant.

Albaro Hiriberhonde

Pundit

Is VersaBond a modified thinset?

The Custom Building Products VersaBond 50 lbs. Fortified Thin-Set Mortar is a professional formula, all-purpose mortar, polymer-modified to provide good bond strengths. VersaBond cures quickly and adheres to most surfaces.

Alby Angelkorte

Pundit

How long does modified thinset take to dry?

The humidity, temperature and air flow in a room affect how long it takes to dry, but thinset generally is cured and ready to walk on or grout in 24 to 48 hours. Some installers and home specialists recommend waiting 72 hours for tiles applied to floors.

Meliza Antoine

Pundit

Zdenek Naikari

Pundit

Can I use unmodified thinset on plywood?

?Thinset is the wet base that you first trowel on the plywood to make the tile stick. Higher latex content is essential for bonding to plywood. A quality unmodified thinset should be used and mixed with a latex additive. One example would be to use Laticrete's 317 thinset mixed with Laticrete 333 liquid latex additive.

Marjan Cajo

Teacher

Is there a difference between Thinset and mortar?

mortar /môrter/noun: a mixture of lime with cement, sand, and water, used in building to bond bricks or stones. Thinset, while it is also sometimes referred to as a “mortar” is an adhesive. It's a mix of cement, water, and fine sand. It is usually used to attach tile or stone to surfaces such as cement or concrete.

Prospero Keunecke

Teacher

What size trowel do you use for Ditra?

For DITRA use a 1/4" x 3/16" (6 mm x 5 mm) V-notched trowel, 5/16" x 5/16" (8 mm x 8 mm) V-notched trowel, or the DITRA trowel, which features an 11/64" x 11/64" (4.5 mm x 4.5 mm) square-notched design, is recommended.

Aizpea Marruchipi

Supporter

Can Thinset be used as grout?

Thinset mortar is an adhesive and binds the tile to the subfloor beneath. Grout is a filler used in the joints or gaps between the tiles. The products aren't interchangeable. Using mortar as grout to fill in the cracks could cause problems for your floor over time.

Rozica Stenmans

Beginner

Can you use thinset to level a floor?

You can use thinset to install tile over an uneven cement floor and leave the floor perfectly level. You can also use thinset mortar to level out an uneven cement floor or fill small holes in the floor without installing tile.

Darrell Berriozabal

Beginner

Can you use modified thinset over Kerdi?

Modified thinset mortars aren't recommended for use with Kerdi because they must dry out to gain strength, whereas the membrane inhibits drying, which can lead to unpredictable results. For example, if a shower is used before the mortar has cured properly, leaks and polymer leaching can occur.

Sajad Andres

Beginner

What type of thinset do I use for Kerdi?

Unmodified thin-set mortar is recommended to set ceramic and stone tile, including large format tiles, over the KERDI membrane. Portland cement-based unmodified thin-set mortars are dependent on the presence of moisture for hydration in order to gain strength.

Traian Oldenbostel

Beginner

Can I use thinset for shower floor?

Because thinset is not affected by moisture, it is best for floor tile and any tile in wet areas, including shower floors, walls, and ceilings and tub surrounds.

Lira Padovan

Beginner

Do you have to use thinset under cement board?

Since you are putting down hardie board on boards with small gaps, I would not recommend trying to put down thinset under it. It will make an enormous mess under the house (or whatever is under your bathroom). It is also more likely to make the floor uneven since it is hard to level thinset that is separated by gaps.