Once roof preparation is done, layout the three most critical chalk lines that will serve as guidelines to the shingles which are placed along these lines and nailed in place.
The horizontal chalk line keeps the rows in a straight line while the vertical chalk line keeps the courses square in an upright straight line. The horizontal chalk line measurement is the width of a shingle which is 133/8".
The rake chalk line gives roofer a guideline to follow when cutting off the excess shingle overhang.
To start the horizontal chalk line, find a comfortable and safe location near the lower end of roof along the fascia board roof line and with measuring tape, mark 123/8" from edge of overhang up. Although the shingle width is 133/8" wide, 123/8" is used to obtain a one-inch shingle overhang over facsia board and rakes. (barge board) Do the same to opposite end and connect the two marks with a chalk line strike.
Repeat the process to the rake chalk line which is up the incline roof surface on both ends. The rake chalk line has the same measurements as the horizontal chalk line (123/8" plus one inch for overhang)
To mark the vertical chalk line use the shingle length (393/8") as the measurement, but mark 383/8" instead (allowing one inch for shingle overhang again) from edge of plywood (rakes) inward along the horizontal chalk line at the lower end and top end along the ridge. Use chalk line and snap a line between the two points, but extend the chalk line pass the horizontal line all the way down to the edge of fascia line to get a complete line.
Before shingles are nailed in place the vertical and horizontal chalk line must be perpendicular or at right angles ( 90 degrees) to each other.
Check the lines for square by using the Pythagorean theorem of 3:4:5
method. In a right angle triangle with sides of 3, 4, and 5, the
sum of square 3 and 4 is equaled to square of hypotenuse which is 5.
eg: 3x3=9
4x4=16
5x5=25
On an average roof inclined surface of 16 feet, double or tripple the 3:4:5 method for larger measurements to check roof square - 6:8:10 or 9:12:15.
Where the two lines intersect, measure four feet up the vertical line and place a mark (labeled A) and on horizontal line measure three feet out from intersecting point and mark B. The distance between point A and B should measure five feet. If the measurement is more or less than five feet then adjustments would have to be made.
We'll talk about that in the next article.
Go To Page: 1 2
