If the sub floor is rough, it can be leveled with Quick Patch. This is similar to concrete, but is easily mixed with water. It should be like a honey consistency. Spread and smooth out. If any high spots appear, they can be scraped smooth with a tool with razor type blades. No need to sand.
Once the floor is ready, begin at the center of the room. Never at the walls.
Measure across the length of one wall, mark the center. Measure across the other length wall, mark that center.
Strike a chalk line from one mark to the other.
Follow the same procedure along the width of the two walls.
Strike a chalk line
Now you have both lines intersecting at the center of the room.
NOT THROUGH YET!
You must be certain the the two intersecting lines form perfect 90 degree angles.
To do this.
On either the horizontal or the perpendicular lines, accurately measure from the intersection, out to a distance of 3 feet.
On the other line, accurately measure from the intersection, out to 4 feet.
For clarity, lets name the intersection, A.
From A out to 3 feet, name the point, B.
From the A out to 4 feet, name that C.
This is a right triangle.
NOW! Measure the distance from B to C. This is the hypotenuse of the triangle. This distance MUST BE 5 feet.
More or less, and the intersection at A are not 90 degrees.
(See my explanation at the end)
This can occur because walls are not always square at corners and thus, not perfectly parallel with the opposite wall.
If the hypotenuse is more or less than 5 feet. You must adjust the lines at intersection A, until they form 90 degree angles, resulting in the hypotenuse to read 5 feet.
All this is critical in order to begin square.
NOT DONE YET.
Even though intersection A is now square, you MUST check one more thing.
Along each line, from intersection A, lay a row of loose tiles up to the walls in both directions. Use the spacers which you'll use for spacing for grout lines.
When you get to each wall, you may/should have a space, less than a full tile.
Measure the width of the space and compare it with the opposite wall.
You want those to be as nearly equal as possible. These are "fills" which will require cutting the tiles to fit flush to the walls.
DON'T FORGET Doorways. Tiles will extend partially into the openings.
Now, in order to adjust for the "fills", you must move the tiles in one direction or the other about "half the difference" in the measurements of the spaces/fills.
This will result in the fills being about equal, AND, you will avoid any possibility of having fills much more narrow then the opposite wall, or worse, having fills of about an inch and the opposite wall about 6-7 inches.
I hope you can follow this.
Now, you should be able to lay the tiles from the absolute center of the room in both directions.
The centers of the tiles should align with the corrected chalk lines.
Spread the thin set adhesive in small areas at one time.
Begin by laying tiles, left and to the right, in a stair step fashion.
Use the spacers to space the tiles for grout.
This method will allow you to check the square as each tile is placed into the corners of the "stair step".
After the entire room is done, then go back and fill along the walls.
Measure the distance from each tile to the wall, from the left and right corners of the tile, considering the spacers. CUT EACH TILE separately. Do not cut more than one tile at a time.
Trust me, the walls are not square and will run at an angle, and each fill tile may be a fraction more or less than others. This may require that the wall edge of the tile be "cut out of square" in order to follow the walls..
You can grout along the walls as well as the tiles.
Explanation of right triangle.
Since the hypotenuse of a right triangle is equal to the Square Root, of the Sum of the Squares of the other two sides, this is how it works.
Side A:B = 3 feet, squared = 9.
Side A:C = 4 feet = squared = 16
Added together = 25.
The square root of 25 = 5 = the hypotenuse.
This site may help.
If this is unclear, you're welcome to contact me. below
35 years flooring owner. Ret.
· 1 decade ago