How To Measure

Estimating Materials Needed

In order to arrive at the amount of siding necessary to cover a house, the measuring operation can be reduced to simple steps. All houses can be broken down into the shapes of rectangles or triangles, or a combination of both.

Using the formulas below, the area can be determined by measuring the the height and width of the house (including windows).

Next, determine gable triangle areas by using the formulas below. Total all these areas. Windows and doors are not generally deducted. Including them in wall area figures will provide an allowance factor for waste. If the window and door areas are extremely large (such as garage doors, or sliding glass doors) some deduction might be made.

Dormers and gables are traditionally prone to material waste due to cutting and fitting; to compensate, add one foot in height to the original measurements to allow for waste.

For the amount of starter strip required, measure the lineal feet around the entire base of the building to be covered, then divide by 12, since starter strip comes in twelve foot lengths. For corner posts and accessories, also measure in lineal footage. Total footage of corner posts is then divided by 10, since they come in 10 foot lengths. All channel, drip cap, and finish trim come in 12 foot lengths and total should be divided by 12. When measuring lineal footage, add a factor of approximately 10 percent to allow for waste.

Click Here for a Measuring Worksheet You Can Print Out and Use!.




Rectangle : Base (B) x Height (H)



Triangle : Base (B) x 1/2 Height (H)



Trapezoid : Height (H) x Sum of the Parallel sides (PAR+PAR)



Gable Ends : Width (B) x 1/2 Height (H)



The Side of a Dormer is a Triangle : Base (B) x 1/2 Height (H)



For a Gambrel House :
1/2 (B+C) x H



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