Figure 1 - House with a Gambrel gable that has siding
Calculate how much siding is needed for a gambrel gable as shown in Figures 1 and 2.
Figure 2 - Measuring Gambrel gable for siding
Half of (D-C) X B =
Half of C X (A-B) =
B X C =
Total For One Gambrel Gable =
As an example:
A = 9'; B = 5'; C = 20'; D = 30'
1/2 ( 30 - 20 ) X 5 = 1/2 X 10 X 5 = 25
1/2 ( 20 ) X ( 9 - 5) = 10 X 4 = 40
5 X 20 = 100
The total square footage for this Gambrel gable is: 165
The side of a dormer is a triangle, but as there are two sides, the calculation is actually quite simple.
Figure 4 - Measuring a roof dormer for siding
If both sides of the dormer are the same dimensions, the formula is (for both sides - do not multiple times 2):
Length X Width =
If it is necessary to calculate the sides of the dormers individually, the formula for each side of the dormer is:
1/2 X Length X Width =
Once you have calculated all the areas that you wish to have sided, add the numbers together. Then deduct any major non-sided areas, such as garage doors and bay windows. The resultant number is how many square feet of siding you need to cover the areas of the home you wish to be sided.
The starter strip is the trim that goes all the way around the perimeter of your home, as shown in Figure 5. It is the trim piece that the first sheet of siding will lock into.