For a roof with slope 6 in 12, the factor to convert plan area to actual area is

For a roof with slope 6 in 12, the factor to convert plan area to actual area is

• A. 1.014
• B. 1.031
• C. 1.054
• D. 1.118

Answer: (D)

When you convert plan area to actual roof area, you multiply by a factor that accounts for the slope. That factor is the square root of 1 plus the square of the rise-to-run ratio: sqrt(1 + (rise/run)²). For a 6 in rise over 12 in run, rise/run = 0.5. So the factor is sqrt(1 + 0.25) = sqrt(1.25) ≈ 1.118. So multiply plan area by about 1.118 to get the actual roof area. The other values would correspond to gentler slopes and don’t match a 6/12 pitch.

When you convert plan area to actual roof area, you multiply by a factor that accounts for the slope. That factor is the square root of 1 plus the square of the rise-to-run ratio: sqrt(1 + (rise/run)²).

For a 6 in rise over 12 in run, rise/run = 0.5. So the factor is sqrt(1 + 0.25) = sqrt(1.25) ≈ 1.118.

So multiply plan area by about 1.118 to get the actual roof area. The other values would correspond to gentler slopes and don’t match a 6/12 pitch.