The Roof Sheathing for One Sided calculator computes the number of 4x8 sheets to
cover the area of a one sided roof based on the ridge length, span, overhang and pitch.
INSTRUCTIONS: Choose units and enter the following:
- (L) Ridge Length
- (S) Span
- (P) Pitch (choose: flat,1/12,2/12,3/12,4/12,5/12,6/12,7/12,8/12,9/12,10/12,12/12,14/12)
- (oH) Overhang
4x8s for a Sloped Roof (n): The calculator returns the number of 4x8 sheets needed to cover a shed roof and the total square footage.
The Math / Science
The surface area of a roof is the length of the trusses
times the ridge length.
A = TL * L
The truss length can be computed using the span (S), overhang (oH) and pitch (P) as follows:
Pitch Angle (α) = atan(P)
TL = (S+oH) / cos(α)
where
- TL = Truss Length
- α = pitch angle
- S = Span
- oH = Overhang
- P = Pitch
A simple solution is to compute the area (A) and divide by 32 ft2, the area of 4x8 sheet. However, this does not appropriately account for how 4x8s are used, specifically how cut-offs are reused. This algorithm provides an accurate an conservative number of 4x8 sheets for a shed roof, based on normal construction methods.