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4 Ways to Avoid Mortar Missteps

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Innovations in mortar technology have made it easier to meet the specific demands of a variety of jobs. However, mortar is only as good as its installer, and forgetting installation fundamentals can result in callbacks and job failures. Help avoid costly mortar missteps with the following four basic – but crucial – techniques.

1. Prepare the substrate

To achieve a proper bond and reduce callbacks, the first step is to properly prepare your substrate before installation begins. Surface preparation can be as easy as sweeping the floor or wiping it with a damp, clean sponge before beginning to set tile.

If your substrate’s variation exceeds acceptable flatness tolerances, you’ll need to do more than just clean the surface. In these cases, use a patching product or self-leveling underlayment as needed. Taking the time to properly prepare your substrate is an important step. If the work is extensive, be sure to get a signed change order before you begin.

2. Select the correct mortar for the job

You have a vast array of mortars at your trowel tips. Too often, mortars are selected based on cost. But choosing the wrong mortar can cause installation failures that are far more expensive, putting your project and reputation at risk.

For large format tile installations, don’t settle for trying to build a standard modified mortar up to 1/2” or 3/4” thick. Standard mortar, unlike medium bed mortar, is not designed to maintain a 3/4” thickness. For that reason, it may shrink and cause lippage when used with large format tile.

Tiling floor by master

If you’d like to take the guesswork out of which mortar to choose, two such highly versatile mortars are offered by TEC for virtually any tile installation: TotalFlex 150 and TotalFlex 110. The TotalFlex mortars were engineered to combine maximum versatility (99% of all applications) with extremely long open times of up to 60 minutes. Both mortars are also warrantied to work with any uncoupling membrane for either crack isolation or waterproofing, so you can use them over or under the plastic sheeting or mats put in place. 

3. Control the climate

Tiles at work. laying of ceramic plates, wood pattern.

Outdoor installations in four-season regions present a particular set of installation challenges. If left under the hot summer sun, thin set mortar will set up too fast – as if you had mixed it with warm water. Direct sunlight on hot, dry days can cause mortar to lose its moisture to the atmosphere. This weakens the mortar and might not allow it to hold up over time. For better results, protect the installation from direct sunlight by tenting.   

Cold temperatures present the opposite problem. Optimal temperatures are between 50 – 70°F (10  – 21 °C) prior to install and for 48 hours after. Don’t install if freezing is imminent or cannot be protected against. Whenever installing in cooler temperatures, be sure to keep the extended cure time in mind during and after installation.

Whether it’s hot or cold outside, you also need to account for wind or air movement. Any wind will remove water from the mortar and dry it out. You can prevent this simply by protecting the surface area with a tent or sheets of plywood to cut the wind.

4. Achieve proper coverage

If you’ve prepared your substrate, selected the proper mortar and taken climate into account, you’re ready to begin troweling. Remember, average contact area for tile should be at least 80 percent generally and increases to 95 percent in exterior, shower, or wet area installations. Natural stone, however, requires a contact area of 100 percent. Be sure to follow proper trowel selection and troweling techniques to meet these requirements.

To check that you’re achieving proper coverage, periodically pull up a tile immediately after placing it, then look at its backside to see how much contact and coverage you’ve achieved. That way, you can verify that you are using the right amount of material and notch size.


Article written by Chris Kain.

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