General Contractor Practice Exam

If a roof has a slope of 1/4 inch per foot, what is the maximum height of insulation if the roof drain is 6 inches high?

1. 8 inches

2. 10 inches

3. 11 inches

4. 12 inches

The correct answer is: 11 inches

To determine the maximum height of insulation on a roof with a slope of 1/4 inch per foot, you must understand how roof drainage works and how the slope affects water flow. The given slope means that for every foot of horizontal distance, there is a vertical drop of 1/4 inch. Since the roof drain is 6 inches high, this is the total vertical distance available before water reaches the drain. To calculate how much insulation can be installed while still allowing for effective drainage, you should first convert the vertical distance from inches to feet. Six inches converts to 0.5 feet (since there are 12 inches in a foot). With this information, the total slope from the edge of the roof down to the drain must be computed. In this case, if you consider the roof as sloping towards the drain, for every foot of horizontal run, you're looking at a fall of 0.25 feet (or 3 inches). Therefore, if we want to find the maximum height at the edge of the roof where insulation can be installed, you can calculate how high the insulation can go before it reaches the drain. Starting from the height of the drain (0.5 feet), you need to calculate how many feet