“Mortar products today are so much better than they were years ago,” said new NTCA president and NTCA Technical Committee chairman James Woelfel, of Artcraft Granite, Marble and Tile Co., from Mesa, Ariz. “That’s why you don’t see as many failures as you ‘should’ see, if you were using mortars from 30 years ago.
“Mortars today are so fantastic,” Woelfel added. “Today, we have flowable/thixotropic and non-sag mortars. They are phenomenal – but they are a double-edged sword,” he said, stressing that if they aren’t used properly, the installation will fail spectacularly.
Woelfel – together with several technical representatives from manufacturers who have collaborated on authoring and editing the mortar section of the NTCA Reference Manual- have some important recommendations for getting the best results from today’s mortars.
Use the right material for the job
An obvious – but oft-ignored recommendation – is to use the proper mortar for the proper tile, Woelfel said. “The more expensive mortar doesn’t cost you more than $.05-$.07 a foot or maybe all the way up to $.15 more a foot,” he explained. “By using the right mortar, you are really buying yourself insurance. Since mortar is the least expensive part of a tile installation, if you are depending on the savings on that mortar to make you a profit, you are going down the wrong road. And if you are improperly using an inexpensive mortar, and building it up, are you really saving money in both material and time?”
Water ratio – follow directions, not intuition!
Second, be sure to mix the mortar the way the manufacturer recommends.
“The mortars being built today are very complex formulations and a lot of ingredients in these formulas require the proper amount of water,” said Leigh Hightower, technical services manager for MAPEI. “Contractors are used to mixing mortars to feel, but today’s mortars have a lot of materials in them that don’t wet out very quickly. If the mortar looks too thick as it is being mixed, and more water is added when it is mixed up, when it does go into solution, it is too thin. Mortars today need to be mixed with a measured amount of water according to instruction and not feel,” he said.
Tom Plaskota, with TEC/H.B. Fuller Construction Products, added, “job site conditions can affect installation and temperature-range limitations are pushed to the limit with the pace of fast track construction these days. This occurs on both the low and high ends of the temperature range, depending on what part of the country you are in and what time of year it is.”
Woelfel cited some of his experiences setting tile in the desert climate of Arizona. He said it’s easy to “overwater thinset in dry climates; there’s more chance to shrink here as it dries. Thin-set mortar sets up faster in Arizona and New Mexico – in fact, in Arizona this June, we set a record for 2% humidity.”
Woelfel said this is a problem because even if one is following strict manufacturer recommendations, those recommendations generally aren’t based on use in extreme conditions. “[Mortar is] tested at 75 degrees and 55% humidity,” Woelfel said. The tendency for mortars to skin over too fast in low-humidity settings is especially crucial when working with large-format, or large thin porcelain tile. Once that happens, there’s no bond.
Woelfel favors the development of more mortars that accommodate the particular conditions contractors encounter around the country – high humidity, or super-low humidity – so contractors have a reasonable amount of open time to set the tile.
“Most people in my area are subcontractors,” Woelfel said. “They are putting tile in as fast as humanly possible, which means they will trowel out 40’ to 50’ of thinset and just drop the tile. They don’t key it in, and it stays on top of the trowel marks. When it’s pulled up, it’s almost clean. There are a lot of failures in Phoenix due to mortar skinning over,” Woelfel said.
Bubbles weaken bonds
Woelfel also cautions contractors to take time with mortars and let them slake. “You need to mix with a low rpm mixer at the proper speed that the manufacturer recommends,” he said. “Otherwise, you can get air bubbles, which makes the mortar set up faster and become weaker. You have to let it rest and coalesce.”
A new name and clearer definition
Large and heavy tile (LHT) mortar, has gone through a transformation – and not just in name only – from the previous “medium-bed” mortar moniker. “Medium-bed” mortar was coined to refer to a MATERIAL – a type of mortar, not a METHOD of tile setting, according to MAPEI’s Hightower. But over time, it became misunderstood and mis-specified in the A&D community as a method of smoothing out imperfections in the substrate in lieu of the proper practice of using a self-leveling underlayment. Contractors got caught in the middle, Hightower said, when they started to be expected to smooth out substrate irregularities with medium-bed mortar, used up to 3/4” in thickness instead of going the proper route of using a self-leveling underlayment. The industry responded to this conundrum by changing the confusing name and limiting the thickness recommended to 1/2” to avoid misuse of this important material. For more information, check out this month’s “By the Book” section in which ProSpec’s Beverly Andrews talks about new parameters for use of LHT mortars or what we formerly called “medium-bed” mortar.
Up-and-coming products for LTPT
LHT mortar segues into mortars many manufacturers are developing specifically for large-unit thin porcelain tiles. These mortars are tied in closely with the standards discussions about large thin porcelain tile (LTPT). As these mortars are in development, contractors are offering feedback on realistic performance criteria. Some manufacturers required 1/64” lippage tolerance, Woelfel said – something unattainable with bigger thin tile. This is where the NTCA Technical Committee, TCNA and other industry entities are putting their heads together to formulate products and methods that will meet the needs of the contractor with excellent performance while the large thin porcelain tile itself is under close scrutiny in terms of performance characteristics and installation recommendations. Stay tuned to TileLetter for ongoing news about LHT mortars for LTPT throughout the year!