RRC Roof Drainage & Slope Design 2

Question 1

What is a 'cricket' or 'saddle' used for in roof design?

Accepted Answer

A peaked diverter built on the high side of a penetration to redirect water around it

Answer

A decorative ridge element on steep-slope roofs

Answer

A type of strainer placed over roof drains

Answer

A temporary water diversion measure used during re-roofing

Question 2

At what height above the roof surface is the inlet of an overflow drain typically set?

Accepted Answer

2 inches above the roof surface

Answer

Flush with the roof surface

Answer

4 inches above the roof surface

Answer

6 inches above the roof surface

Question 3

What is the primary design purpose of a tapered insulation system on a low-slope roof?

Accepted Answer

To create positive drainage slope on a structurally flat deck

Answer

To maximize thermal R-value uniformly across the roof

Answer

To reduce total insulation material costs

Answer

To provide a smooth substrate for single-ply membrane application

Question 4

The design rainfall intensity used for roof drainage calculations is typically derived from which data source?

Accepted Answer

NOAA precipitation frequency data (Atlas 14)

Answer

ASHRAE Fundamentals Handbook climate data

Answer

Local building department historical records only

Answer

Manufacturer-specified rainfall assumptions

Question 5

What is the standard formula for calculating required roof drain flow rate (Q in GPM)?

Accepted Answer

Q = A × I / 96.23 (A=sq ft, I=in/hr)

Answer

Q = A + I × 2.0

Answer

Q = A × I × 0.50

Answer

Q = I / A × 100

Question 6

What is the most serious consequence of chronic ponding water on a built-up or modified bitumen roof membrane?

Accepted Answer

Accelerated membrane deterioration, blistering, biological growth, and potential structural overload

Answer

Increased UV reflectance of the membrane surface

Answer

Improved adhesion of aggregate surfacing materials

Answer

No significant effect on properly installed membranes

Question 7

A roof with a 20,000 sq ft drainage basin and a design rainfall intensity of 4 in/hr requires a minimum drain capacity of approximately how many GPM?

Accepted Answer

832 GPM

Answer

208 GPM

Answer

416 GPM

Answer

1,040 GPM