GGCL Guide on How do I prepare the surface before setting porcelain slabs

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GGCL Guide on How do I prepare the surface before setting porcelain slabs

We’ll walk you through the main steps, including key tools and pitfalls to look out for in your tile install job, as you take a run at prepping, tiling and grouting.

Part one will cover the most important and often the most overlooked step: preparation. Tiling relies heavily on proper surface and substrate preparation. To say that it is crucial would be an understatement and that’s why it gets its own special part of this series. Part two we will go through the meat of how to actually tile and grout a floor.

So let us jump in and look at what you will need to start preparing your floor for tile installation, including the tools and some things to look out for when attempting this primary stage of the project.



Here is a quick rundown of tools you will need to prep your floor and space for tile installation:

  • Safety & Comfort
    • Goggles or Safety Glasses
    • Knee Pads
  • For Prepping a Plywood Subfloor
    • 1/4” Cement Board
    • Backer board Screws
    • Saw
    • Crack-Prevention Membrane
  • Squaring Room
    • Tape Measure
    • Chalk Line
    • Carpenter’s Square
    • Hairspray (optional)


No systematic instructional is 100 percent exhaustive. Every project is different, and in your own home, you will inevitably encounter something not covered by this or any tile tutorial. However, if you follow these steps, generally, you’ll find success in your project.

Step 1: Prep the Subfloor

If there’s one step that’s the most important, it’s this one. This one is key. First things first, what exactly is a subfloor? It’s a catch-all term for the floor underneath your finished floor. Two primary types of subfloor: wood and concrete. Both suffer from the same tile-killing issue: movement. Wood moves and flexes with humidity and changes in temperature; concrete can move depending on humidity, moisture, soil movement, and temperature.

Concrete Subfloors

For concrete subfloors, make sure you remove any old adhesive, and patch/fill any cracks with the appropriate product (check your local home improvement store installation products. The recommended patch item varies based on the size of the crack to be filled). Use a floor scraper to remove any loose debris. For old adhesives or mortar, this may require some elbow grease and possibly a grinder to remove from the subfloor and allow the new mortar to bond.  Floor tiles can be installed directly onto a concrete subfloor.

Make sure your subfloor is clean and free of debris.

Step 2: Determine Starting Point and Practice Lay Pattern

Laying out your tile pattern, planning for fixtures, cabinets, etc., in advance is critical to minimizing waste (less cuts!) and making the job go as smoothly as possible.

There are many patterns to choose from, though some work better with specific tile shapes and sizes. Herringbone, brick bond, and basket-weave/parquet are very popular in recent years. You should determine this prior to selecting your tile, but if you’re using traditional square tiles, a linear or grid pattern is timeless and easy to install. This is tile laid next to each other, in the pattern you are envisioning in your mind as you read this. Yes, that one.

Determine your starting point in the room. Typically, you will want full tiles in the most visible or focal points in the room, and cut tiles against cabinets or less visible walls in the room. Measure your room to determine the center, and snap chalk lines on the floor to guide your installation. Make sure to leave equal space at either side so you do not tile up to one side with a full tile and have a partial or cut tile on the other. Every space is different, so take your time and plan accordingly. The goal is to get as many full field tiles down on the floor and leave the custom cuts for around obstacles, under appliances, and against the outside wall areas.

How to Square a Room for Simple Tile Installation

For most simple applications, floor tiles can be laid out in a grid pattern that starts at the center of the floor, so that cuts at the edges of the floor will be consistent at opposite walls. To achieve this, one method is to divide the floor into four quadrants that intersect in the middle of the room. These quadrants should be square to each other; however, this may be an issue in older homes where the room itself is unlikely to be truly square. Do not rely on the wall positions to set up your grid, but rather square it yourself at the center.

  1. Measure one side of the floor, find the middle and mark it with a pencil. Do the same along the opposite side of the floor.
  2. Snap a chalk line across the floor, from one mark to the other. Spray with hairspray to keep the line from smudging.
  3. Measure and mark the middle for the two remaining sides of the floor. Lay the snap line from one mark to the other so it intersects the first line in the center of the room. Don't snap the line.
  4. Lay a carpenter's square at one of the four corners of the intersection created by the chalk line that you laid first and the string. If the line and the string are truly perpendicular, then each will run right alongside one edge of the carpenter's square.
  5. Adjust the string, if necessary, so it is completely square against the chalk line. Once the string is square to the line, snap the string.  Spray with hairspray to keep the line from smudging.
  6. Start laying your floor tile, using the center + as your starting point. If you're laying tile, you don't have to leave any buffer space around the edges, as tile does not expand or contract like other flooring materials would.

When to Not Start in the Middle of the Room

At times, centering a room is not necessarily the best layout for your floor tile application. You would start from the middle of the room if the space is a simple rectangle or square shape similar to the diagram above, and the only room being tiled.  Example, a wide-open square or rectangular room. This could be a dining room or an open bedroom.

In a kitchen, you would not just center the room.  You would lay your full tiles at the transition to the larger adjacent room, typically the living room.  Then the cut tiles would go against the walls and at cabinets.

In a hall bathroom or laundry room, you would start with full tiles at the door .This would put your cuts against your cabinets and behind your commode and against the tub/shower; or under your appliances if in the laundry room. In these areas, the entry and main walls are the focal point.

In a master bath, you would typically start a full tile at the entrance door.  Unlike a standard hall bath, many times a master bath’s focal point is the tub and shower side of the room, so put your full tiles against the tub and/or shower and allow the cuts to land at the cabinets. This does depend on the layout of the room.

Whether you decide to begin in the center or at a focal point, chalk guidelines are still a great first step, as they can ensure your final layout is straight and parallel. Practicing with a dry layout of your tile can help you determine what is the main focal point in the room, and the best place to begin.