How to Draw Plumb Lines on the Ceiling

Place a ladder at one side of the room and another ladder at the other side of the room. Stretch out a tape measure and climb up on one ladder while an assistant climbs up on the other ladder. Measure the entire length of the room from one side of the ceiling to the other and write the measurement down.

Divide the length in half and move the ladders to the midsection of the wall. Stretch out a chalk line between the two ladders and hold it up to the ceiling. Pull down on the chalk line and release it to draw the first plumb line on the ceiling.

Reposition the ladders on the walls that run the width of the room and measure them using the tape measure. Divide the measurement in two and then reposition the ladders at the midpoint of that wall.

Stretch the chalk line between the two midpoints and snap it against the ceiling, just as you did previously, to create the second plumb line.

Measure the width of the object you are installing on the ceiling, such as a ceiling tile. Measure the same distance from one of the center lines and stretch the chalk line across the room over the location. Snap it to create a parallel line next to the center one to designate the first row of tiles.

Repeat the process of snapping new chalk lines all the way across the ceiling until you have a grid of plumb lines that indicate where each row goes.