I’ve spent the past few days with Jim from Diamond Tile located here in Maryland, and if you remember, I’ve partnered with Jim and his brother Rich before to cover topics like How to Grout a Tile Floor and How to Pour a Shower Pan. Jim and Rich both have over 27 years of experience and possess a wealth of knowledge, and I’m pleased to be back on a job site with Jim (Rich is out after back surgery) as he tiles a kitchen floor.
Regular readers will know that today’s article is part of a series with professional contractor Joe Bianco as he and his crews complete a total kitchen remodel. If you’d like to read more, here’s the progress on Day 1.
Flashing the Floor
After an initial walk through, Jim recognized that this floor would need some work before it was ready for tile, and the first step is to flash the floor. Jim isn’t concerned about leveling the floor but rather eliminated peaks and valleys that would cause tiles to crack. These areas are commonly found along joists where the floor sags between them.
Pro-Talk: Tile contractors often use the term flashing and evening a floor interchangeably.
Pro-Tip: Jim estimates that 9 out of 10 remodel projects require the floor to be evened before tile.
Step 1: Clean the Floor
Like many of our Pro-Follows, this one starts with cleaning the floor, and Jim used a trowel to scrape away drywall compound, dirt and any flaking OSB.
Pro-Tip: While not present on this job, paint should be removed from the floor before laying tile because paint can prevent the thinset from creating a strong bond. Paint can be scraped or ground away, or it can be removed with chemicals. Each method includes caveats. For instance, scraping paint off a floor is labor intensive. However, paint should be tested for lead before grinding and chemicals often require a cleaning solution afterward.
The previous floor had a layer of luan which was (excessively) stapled down, and Jim had to go over all the staples to make sure they wouldn’t interfere.
Jim also removed the brass transition strip over the threshold, and swept everything clean.
Here’s a composite image of the kitchen floor after Jim was finished cleaning. There’s a little discoloration where the sink was located. However, the floor is sound and not in need of any further repairs.
Step 2: Checking the Floor
Jim is experienced enough to be able to walk a floor and look for uneven areas and excessive bouncing. Even so, he uses a level or straight-edge to better understand where the high and low areas exist.
You can imagine how time-consuming this process can be so instead Jim used the all new Bosch GSL-2 Surface Laser to pinpoint where the floor was uneven.
To use the GSL-2, Jim set it up in several places to check the floor (relative to the location of the GSL-2).
Where the two lines perfectly coincide, the floor is flat and level. If the two lines diverge, the floor is uneven and out of level.
Step 3: Mix Tile Mortar
To even the floor Jim used Mapei’s Kerabond tile mortar with Mapei’s Keralastic additive.
Keralastic is a latex additive which enables the mortar to better adhere to the subfloor. Jim mixed up a 5 gallon bucket full of mortar and let it slake for 5 minutes before mixing it again.
Pro-Talk: Slaking is the process of leaving the mortar undisturbed to allow the water to completely penetrate the dry ingredients.
Pro-Tip: Over a concrete subfloor, the Keralatic additive is not necessary.
Pro-Talk: Latex additive is often called milk because that’s what it looks like.
Step 4: Spread the Mortar
Jim used a notched trowel to spread a portion of mortar, concentrating on filling low areas. Next, he used a screed board to smooth the mortar.
Pro-Tip: Jim says the most common mistake when laying tile is failing to prepare the subfloor.
Step 5: Feather Edges
Around the perimeter, Jim used his trowel to feather the edge for a smooth transition.
Jim stopped often to clean the screed board with a trowel and sponge.
In this way Jim spread the mortar to even the floor, and he completed flashing the kitchen in three passes.
You can already see that the mortar is thinner along the length of a couple of joists and thicker in the adjacent valleys.
Jim let the mortar dry overnight before starting the next step. Stay tuned to see how Jim installed Schluter Ditra uncoupling membrane in our next Pro-Follow.
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