Construction of a gable roof, part 2
How to designate a rafter?
MEASUREMENT METHOD
roof slope (i)= 1/3 (18°, 33% or 0,33)
roof run (a) = 120 cm
roof span (2 x a) = 2 x 120 cm = 240 cm
projection of the end of the eaves rafters = 30 cm
ridge purlin thickness = 50 mm = 5 cm
number of episodes 30 cm of the length of the run = a / 30 cm = 120 cm / 30 cm = 4 sections
The measuring method will be as follows:
– we find height on each 30 cm of the length of the run, which is equal to the slope of the roof (i) multiplied by the roof span (2a) = 1/3 x 240 cm = 80 cm : 4 (four episodes after 30 cm of running length) = 20 cm;
– put the angle bar on the rafter section like this, to the angle points in the distance 20 cm up (item A) i 30 cm at the bottom corresponded to the upper edge of the rafters;
– we mark a vertical line in position A and point B, we move the angle bar to its second position and repeat the previous point,
– we repeat this activity so many times, how many episodes 30 cm is the length of the run (for this example – 4 x 30 cm = 120 cm of running length);
– invert the angle and mark the eaves cut on the eaves rafter;
– place the angle bar in the drawing position and mark the rafter cut on the cap. The minimum contact length of the rafters with the cap is 75 mm;
– finally, half the length of the ridge purlin has to be subtracted to be cut off.
Making a carpentry square (the roof benchmark)
The easiest way to find the length of the rafters is to use a roof angle.
Along the top of the angle bar there are graduation marks from 0 do 60,0 cm with increments of every 2,5 cm. Numbers from 5,0 do 30,0 cm correspond to the height at each 30 cm of the length of the run for all rafters. First line below, described as the length of the rafters on each 30 cm of the length of the run, denotes the length of the rafters on this section of the length of the run under each of the numbers from 5,0 do 30,0. These calculations are given in centimeters and tenths of a centimeter.
Side edge contains number break from 0 do 40 cm z 2,5 cm division of the whole number scale.
