The Sheathing and Cost Estimate for a Roof calculator computes the number of 4x8 sheets (32 ft² each)
needed to cover the area of a basic gabled roof (see graphic) based on the ridge length, roof span, overhang and the pitch and applies the unit cost of a 4x8.
INSTRUCTIONS: Choose units and enter the following:
- (L) Ridge Length
- (S) Span of Roof
- (oH) Overhang
- (P) Pitch of Roof (choose one)
- (uP) Unit Price of Sheathing Boards (see Unit Pricing below)
Total Sheathing Board Cost (TC): The calculator returns the total price of sheathing boards in U.S. dollars. However, this can be automatically converted into other currency units via the pull-down menu.
The Math / Science
This formula is for a basic gable roof that is symmetric on both sides of the ridge. The pitch is defined as the rise over run, which is used to compute the pitch angle which is in turn used to compute the total surface area of the roof. Ideally, the total surface area could be divided by 32 square feet, the area a 4x8 can cover, in order to compute the number of 4x8 sheathing boards. But this would give an inaccurate number of 4x8s, since it implies a perfect utilization of partial pieces of the 4x8s, which is unreasonable. This model attempts to conform to construction habits of reasonable reuse and provides a conservative estimate (higher) on the number of 4x8s.
Unit Pricing
One should always use the local pricing available for constructions. However, for convenience a survey is periodically made for material costs. The following was identified for the price of 4x8 boards.
Most Recent Survey Results:
- Survey Date: 12/4/23
- Survey Store: Menards
- Price of 4x8 3/4" Plywood: $39.68 USD
- Price of 4x8 5/8" Plywood: $34.8 USD
- Price of 4x8 1/2" Plywood: $29.7 USD
- Price of 4x8 3/8" Plywood: $26.89 USD
- Price of 4x8 1/4" OSB: $16.39 USD
- Price of 4x8 3/4" Pressure Treated Plywood: $56.59 USD
- Price of 4x8 1/2" Pressure Treated Plywood: $47.79 USD
Roof Types
