Orange Waffles & Thinset
What was that? Uncoupling isn’t a word that rolls off your tongue regularly? I was in the same boat, but now you can add this one to your vocabulary:
Tile has been successfully installed for thousands of years by incorporating an uncoupling layer, or forgiving shear interface, within the tile assembly. Schluter-DITRA provides uncoupling through its open rib structure, which allows for in-plane movement that effectively neutralizes the differential movement stresses between the substrate and the tile, thus eliminating the major cause of cracking and delaminating of the tiled surface. – Ditra
So basically, this plastic orange waffle membrane allows the tile and the subfloor to move independently preventing cracks in the grout and tile. It’s slightly more expensive than cement backboard but at 1/8 in thick, it was perfect for this project where we were trying to reduce the transition from the tile floor to the existing hardwood in the neighboring rooms.
You MUST use the correct type of thinset OR the whole installation will be done incorrectly, be ruined and cause you a lot of money to rip out and redo.
The right kind of thinset is dependent on the type subfloor you have: wood, cement etc… So please make sure to FOLLOW WHAT DITRA says NOT what the guy in the tile isle at the hardware store says.
We almost botched our job by getting bad advice from one of the sales associates in the tile isle at Lowes. If I hadn’t done extensive research online and on the Ditra website prior to going to the store to buy supplies we would have screwed ourselves. Especially since the guy was so convincing, he almost had me doubting myself. I argued with him for about 20 minutes, and thankfully the tile department head, or whatever, came by and heard us having an intense debate, found out what it was about and immediately confirmed that I was correct in everything I was saying, and his employee was wrong.
1 point for Rachel.
What were the winning installation instructions? Well, if you are using wood as your substrate – which is perfectly acceptable by the way (but I wouldn’t use OSB, just go for the plywood) – I will tell you:
- Wet down the plywood floor with a damp sponge.
- Ditra must be set in a mortar bed. So there is a layer of thinset between the plywood and the layer of Ditra. This secures the Ditra to the substrate (plywood in this case). The Ditra has a fleece backing that grabs the thinset.
- The thinset you use as a mortar bed for the Ditra must be modified. Modified thinset uses air to cure, and so can only be used when one of the two substrates it is sandwiched between is permeable. Permeable substrates allow air and moisture to move through them. Wood does this. So the modified thinset will be able to dry. If you put modified thinset between two impermeable substrates, it will take weeks to dry and you will ruin your tile job.
- Modified thinset has additives that make it stronger and more flexible which are both great properties. If you are putting tile over cement backer board then you would set the backer board in a modified thinset mortar bed on top of the wooden subfloor, and then install the tile on top of the backer board with the proper modified thinset for the type of tile you are using.
- IF you are using Ditra over a wooden subfloor (Ditra replaces the cement backer board) the Ditra is set into a modified thinset mortar bed. THEN you use a UNMODIFIED thinset to lay the tile over the Ditra. It must be unmodified. If you use a porcelain tile like we did, because porcelain is impervious and the Ditra is impervious you can not use a modified thinset because there is no movement of air and moisture for it to cure – so it will not. It will not dry or cure correctly and you will have ruined your installation. By correctly using an unmodified thinset, it will cure in the absence of air (just how concrete can cure underwater) and you will be good to go.
- So please, read the directions.
As the hours fly by:
At first I thought the Ditra would make for a quicker tile installation. INCORRECT. It is a much longer process, unless you are a pro and then I’m sure you can slap it down quickly. I am not a pro so these next few steps took a while:
- Roll Ditra out and cut to length with a utility knife.
- Set into mortar bed, making sure to key it into the floor. I think that is the right word. Meaning, don’t just dump a shovel of thinset on to the floor and start using the notched side of the trowel to spread it out. Use the flat side of the trowel to push the thinset into the substrate to make sure even coverage and adhesion – then you can notch it.
- Roll the Ditra out on the thinset layer and use a grout float or a wooden block to smooth out the Ditra and make sure there is good adhesion. Lift up a corner to make sure the thinset is completely covering the Ditra and the floor.
- Once all of the Ditra is down, you can tile immediately. But first….
- Use the flat side of the trowel to push thinset into the waffles, so that the waffles are completely filled with thinset, no gaps. Do this as you go, a small area at a time.
- With the waffles filled spread a layer of thinset on to the Ditra with the notched trowel.
- Lay your tile, working in small areas.
This video is a great instructional step-by-step: