How to Establish and Use Working Lines

The key to installing flooring that comes in squares—resilient tile, wood block, ceramic tile, and some masonry units—is first to establish accurate working lines.

With flooring that is set in adhesive, mastic, or a thin bed of mortar, you’ll start your installation at the center of a room and work toward the walls. The instructions that follow will show you how to lay out and use working lines for this type of installation. Flooring units set in a traditional thick bed of mortar are laid differently — you begin at one wall and work across the room.

You can’t just lay out working lines parallel to the walls of a room; although the wall may appear to be parallel and meet at right angles, few rooms are perfectly rectangular.

Begin by locating the center point on each of two opposite walls, and snap a chalk line across the floor between the two points. Then find the centers of the other two walls and stretch your chalk line at right angles to the first line, but snap the line only after you’ve used your carpenter’s square to determine that the two lines cross at precise right angles.

Fig. 54-0

Next, to ensure that the border units around the perimeter of the room will have a balanced look, lay a row of loose squares of flooring along each line from wall to wall. Allow for space between squares if you’re installing ceramic tile or masonry units that require grouting or mortar joints. If the space between the last square and the wall is less than half a unit wide, move the center lines the width of a half-tile. Check by laying squares loosely on across to the opposite wall to assure you have adequate spacing.

If you prefer to lay your flooring in a diagonal pattern, establish working lines as described above. Then mark each line at two points 4 feet from the center on either side. From these points, measure and mark the end of a 4-foot line in each direction, taking care to lay your tape measure exactly perpendicular to the center lines.

Fig. 54-1

You should now have an 8- foot square, the center of which corresponds with the center of the room. Snap chalk lines between opposite corners of the square to get diagonal working lines. If your measurements were accurate, the diagonal lines will intersect exactly at a right angle over the center of the room. If they don’t, recheck your measurements.

Fig. 54-2

As a final test to make sure the lines are perpendicular, whether they’re running parallel with the walls or on a diagonal, measure 3 feet along one line and 4 feet along the other, then measure diagonally between these two points; this distance should be exactly 5 feet.

Regardless of the material being installed, the sequence for placing squares is the same. If you’re using a square pattern (see illustration), you can fill in the floor area in quarters or lay flooring over half the room at a time.

Fig. 54-3

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