So you've come here to learn how to install Schluter Ditra / Ditra Heat. We'll keep it simple, but make it informative. Let's start by discussing what it is.
Schluter Ditra / Ditra-Heat are uncoupling membranes that are installed under tiled floors. Uncoupling membranes eliminate the leading cause of cracking tile. Ditra is a protective underlayment that manages moisture for all types of sub-floors. Meaning, it also acts as a waterproofing agent; and can also support a heavy load.
There are many pluses to this Schluter product. To name a few, Ditra is very lightweight; in fact, 95% lighter than backerboard or plywood. It's also thinner, Ditra is 1/8" (3 mm) thick, Ditra-XL is 5/16" (7 mm), and Ditra-Heat is 1/4" (5.5 mm). Tiles can also be installed immediately after Ditra installation, so you're able to accomplish a lot more in a day's work.
Difference between Ditra and Ditra-Heat
Ditra is a polyethylene uncoupling underlay with square cavities and a fleece underside that adheres to cement.
It's a crack isolation membrane used on-top of sub-floor to prevent movement stresses from the sub-floor and to protect the tiles from cracking/popping over time. It's also a waterproof membrane that protects against and manages moisture.
Ditra comes in two sizes as stated above. Ditra-XL is often used when you need to raise your sub-floor a little higher for a smooth transition, or when a larger surface area requires more support.
Ditra-heat is a polyethylene uncoupling underlay with circular pucks and a fleece underside that adheres to cement.
It works exactly as Ditra does, however, it incorporates in-floor heating. Instead of having inverted square picks on the membrane, Ditra-Heat has elevated circular pucks that make it easy for heated cables to embed into. You can use Ditra-Heat without the heated cable, as it gives you an in-between thickness from the regular/XL membranes. But generally, it's used in combination with the heated cables.
Tools You'll Need For Install:
First order of business: DO NOT use premixed thin-set or mastic in any Ditra Installation.
Over Wood Floors: If you're installing Ditra over plywood or OSB, you will need to use a latex (modified) thin-set - A118.11 will be labelled on the bag. This ensures that Ditra will adequately bond to the sub-floor and adheres to the warranty policy.
When you are installing on a wood sub-floor, make sure to clean and dampen the sub-floor with water and a sponge. This will ensure a better bond to the Ditra. Do not over-water.
Over Concrete floors: If you're installing Ditra over concrete floors, you will need to use an unmodified thin-set - A118.1 will be labelled on the bag.
To keep things as simple as possible, you can use Schluter-All set cement. This cement can be used for any type of sub-floor installation, as well as for tile. This is the Trades Buy Sell preference every time.
When installing Schluter membranes onto sub-floor surfaces, the mortar needs to be a fairly liquidy consistency, but also needs to be able to hold a notch.
If you are installing a natural stone tile over a wood substrate, a double layer wood sub-floor is required.
1. Pre-cut and dry-fit the Ditra to the space you are working on. Cut out all vents, flanges, or piping for a flat fit.
2. Once the space has been measured, and the membrane has been cut to fit, apply a thin layer of mortar to the sub-floor with the flat side of the trowel; you want to ensure full coverage before applying notches. After full coverage is achieved, notch the mortar using a 1/4" x 3/16" notched trowel.
Note: Make sure the mortar doesn't dry before setting Ditra. If it dries over, you will need to replace with fresh mortar. The best method for install is to work in sections so this is prevented.
3. After the mortar is placed, start laying your Ditra (fleece side down). Use a grout or wood float to press down the Ditra. You want to ensure that you are pressing out all air bubbles and getting the membrane as flat and even as possible.
Note: Once each sheet is installed, lift the corner to ensure full coverage. If full coverage is not achieved, remove and reapply.
When joining sections of Ditra, DO NOT overlap. Place sheets side by side. If you are looking to achieve full waterproofing, the joints can be covered using Kerdi-Band and thin-set mortar.
4. After Ditra has been installed and pressed out, you can begin to lay your tile.
1. The steps are very similar to Ditra installation, with some minor modifications. Pre-cut and dry-fit the Ditra-Heat membrane to the space you are working on. Cut out all vents, flanges, or piping for a flat fit.
2. Once the space has been measured, and the membrane has been cut to fit, apply a thin layer of mortar to the sub-floor with the flat side of the trowel; you want to ensure full coverage before applying notches. After full coverage is achieved, notch the mortar using a 1/4" x 1/4" (6mm x 6mm) square-notched trowel.
Note: Make sure the mortar doesn't dry before setting Ditra-Heat. If it dries over, you will need to replace with fresh mortar. The best method for install is to work in sections so this is prevented.
3. After the mortar is placed, start laying your Ditra-Heat (fleece side down). Use a grout/wood float or a Ditra-roller to press down the Ditra. You want to ensure that you are pressing out all air bubbles and getting the membrane as flat and even as possible.
When installing Ditra-Heat, try to align the pucks during installation. This will help when installing the heated cable.
Once each sheet is installed, lift the corner to ensure full coverage. If full coverage is not achieved, remove and reapply. (Full coverage picture in Ditra section above).
When joining sections of Ditra-Heat, DO NOT overlap. Place sheets side by side. If you are looking to achieve full waterproofing, the joints can be covered using Kerdi-Band and thin-set mortar.
Tips For Installing The Heated Cable:
You should have a Ditra-Heat-E-HK heating cable sized to fit the space. The heating cable CANNOT be cut to fit. When you select the cable size, be sure to account for any fixtures/walls that you'll need to stay away from when installing it.
Stay 3" (75 mm) away from walls or fixtures, 8" (200 mm) away from heat sources (baseboard heaters, fireplaces, forced air heating ducts, etc...), and 6" (150 mm) away from floor drains.
Two or more cables CAN be connected and controlled by a single thermostat if the current is less than 16 amps.
The heating cable leads must be wired in a parallel pattern according to applicable electrical and building codes.
Installing The Heated Cable:
1. Before the heating cable is removed from the spool and installed, conduct the first set of required tests and record the values in the heating cable test log. The test log is found inside of the cable box. If there is a break in the wire or damage to the cable, return the heated cable to the place of purchase.
2. Mark where the hot/cold splice will be placed, notch the Ditra-Heat matting to fit, and insert the splice. Note that the splice will be located at the base of the wall, where the wires will be running up and into.
3. Press the heated cable between the pucks, at a spacing of 3 pucks (3-1/2" - 9 cm) apart. Do this for the entire install. Placing them closer than 3 pucks together may result in overheating and damage and a wider spacing may create cold spots.
It helps if you map out your bathroom using tape, so you know where the toilet/vanity will place.
4. Install the thermostat sensors between two cable runs, at a distance of at least 24" (610 mm) from the wall. You will need to cut the matting where the sensor lies, just as with the splice.
Ensure that sensors are installed in an area where furniture or mats won't be present. Placing furniture or mats over the sensors could act as an insulation and lower the overall temperature of the floor.
Things To Note:
When you are installing the cable, make sure to leave room for the sensors to be installed.
Do not overlap or allow the cables to cross over or touch.
Do not exceed a run of 10ft (3 m), in this case, the cable must be turned or a u-shape must be created.
When you are installing mortar on-top of the cable, be sure to cover the cable and not nick/cut it with the trowel.
When cleaning grout lines, be very cautious and do not nick the cable with a utility knife or grout tool. Any damage to the cable will result in a full repair or total replacement, depending on the severity.
When You Are Ready To Tile:
When you are installing tile onto Schluter membranes, you will need to use an unmodified thin-set (A118.1).
Be sure to completely fill the square or rounded pucks on the membrane prior or during tile installation. Follow the same rule as Ditra/Ditra-Heat installation and install the mortar with the flat side of the trowel prior to notching.
Note: Some installers like to fill all of the pucks first and trowel the surface flat, allowing the mortar to fully dry before tile installation. Others like to trowel it flat, then notch and install immediately. It's all personal preference; both methods work well.
Once the pucks are filled/covered, apply additional mortar over the membrane using a trowel that is appropriate for the size of the tile. The thin-set consistency will be much thicker than for Ditra install.
Make sure you back butter (skim coat) the tiles before setting onto Ditra. This ensures full coverage and adheres to warranty policy.
You can find a Ditra installation handbook for reference included with each roll, or on their website.
Schluter Products For Install:
You can purchase Schluter trowels that are specifically sized to work with their membranes. They also sell mortars that adhere to their installation guidelines and offer warranty coverage. I have linked both items, and more to Amazon in the descriptions above.
Needless to say, Schluter completely stands behind their warranty. They offer a system warranty, lifetime warranties, and product warranties.
Their system and lifetime warranties are full resolutions, inclusive of materials and labour; they will cover you on the full cost of your project.
When you install their products using one of the Schluter thin-set mortars, your installation may be eligible for lifetime warranty coverage.
Ditra-Heat and Schluter thin-set mortar lifetime warranty require registration. If you used these products in conjunction, register here.
Check out their warranty page for more details.
Where To Buy:
Schluter can be purchased from many of the big box retailers like Lowes and Home Depot, independent or larger tile shops, and of course online. Amazon offers a great selection of Schluter products. Click below to browse through the Amazon.ca web store:
If you have a project that you're particularly proud of, please email us the info and pictures at firstname.lastname@example.org. We would be happy to feature you on our Contractor Spotlight page.