Roofing takeoff for Fire rated decking

Hey Lani! Sorry for the late response on this. I may be misunderstanding this, but are you trying to choose the direction that the area slopes, or is this something else? If this is an area, the direction of the slope in the area shouldn't matter, because regardless of direction, it will yield the same result.

codex is giving me this result.

You’re right to be concerned. For fire-rated decking, the 5' zone starts at the yellow eave and runs up the roof in the green-arrow direction. The red-arrow direction is just the length along the eave.

If the software is forcing the slope/run to start at the green vertical edge and rise left in the red-arrow direction, then it is applying the slope to the wrong dimension.

The practical workaround is:

1. Measure the pink fire-rated decking area as a normal flat/plan-view box:

• Length = along the yellow eave/red-arrow direction
• Depth = 5' from the yellow eave toward the ridge/green-arrow direction

1. Do not let the software use the wrong slope direction for this item.
2. Manually apply the roof slope factor to the quantity.

For an 8/12 slope:

Slope factor = sqrt(8² + 12²) / 12

Slope factor = 14.42 / 12 = 1.202

So:

5' horizontal depth x 1.202 = 6.01' sloped depth

Then:

Fire-rated decking area = eave length x 6.01'

or, if your software gives you flat area:

Flat pink area x 1.202 = sloped fire-rated decking area

Example:

If the eave length is 40':

40' x 5' = 200 SF flat

200 SF x 1.202 = 240.4 SF actual roof surface

So the key answer is: yes, the software’s default slope direction would be wrong for this condition if it is treating the green edge as the eave and applying slope in the red-arrow direction. For this fire-rated decking strip, calculate it from the yellow eave up 5' toward the ridge, then manually apply the 8/12 slope factor.

I think Codex may be misinterpreting how zzTakeoff is calculating the sloped area. Right now, the Sloped Area calculated via is Flat Area×Slope Factor. We don't take into consideration which direction the area was drawn. In the response from Codex (that you posted), it says this is one way to calculate it.

Okay perfect! I just needed to confirm that it doesn't affect the math. Thanks for your help.