Hip Roof Multiplier

The hip and valley factor is a number that is multiplied by the actual run horizontal distance of a common rafter to determine the length of a hip or valley rafter.

Hip roof multiplier.

Divide the rafter length by 12 of run to calculate the roof ratio multiplier. Hip roofs can offer extra living space when a dormer crow s nest is added to a hip roof. Repeat the run not the length of a common rafter for precision the thickness of the ridge board and any eave. Thus a moderate 6 in 12 roof pitch means that the roof rises 6 inches vertically for every 12 horizontal inches it runs.

See the image below for more explanation on rise run and pitch. On a hip roof framing plan the lines that indicate the hip rafters ec ac kg and ig in figure 18 3 form 45 angles with the edges of the building. If the home measures 20 x 40 and has a 7 12 roof then to calculate the slope of the roof follow these steps. Multiply step 1 and step 2 i e.

Multiply 20 and 40 which equals 800. 800 multiplied by 1 16. Students should use the sin cos and tan funtion rather then the multiplier table to calculate the length of the roof members. The value arrived at 928 reflects the square feet of the roof.

It takes some time to get use to these functions. A hip roof is a common roof style characterized by 2 pairs of opposing faces sloping downward from a high peak. A 12 in 12 pitch is a steep 45 degree angle roof. The two shorter legs of this.

For example if you measure 4 inches the pitch of your roof is 4 12. You can see from the plan that the total run of a hip rafter is the hypotenuse of a right triangle. For a more detailed explanation of the roof pitch multiplier see how to find the area of a sloped roof if you know the roof pitch in degrees find the secant of the slope using a scientific calculator for example if the roof pitch is 45 then sec 45 1 414213. A roof s pitch is determined by how much it rises vertically for every foot it runs horizontally.

Remember practice makes perfect. The more you practise the more familiar you become using these functions. Hip rafter ratio length multiplier hrrlm 18 12 1 5 common rafter length multiplier crlm 13 4164 12 1 11803. For regular hips and valleys where the roof sections have the same slope and meet to form a 90 degree angle.

For high wind areas or strong storms a pitch of 4 12 6 12 18 5 26 5 angle is recommended. The following table provides the roof pitch multiplier for roofs of various slopes. Simply locate a roof rafter board place the end of the level against the bottom edge and measure from the 12 inch mark vertically to the bottom edge of the rafter. Hip roofs are more expensive to build than a gable roof.

Find the value of 7 12 from the roof slope multiplier table which is 1 16. The common rafter length can be calculated by the roof ratio length per 12 of run.