COMMITTED TO SERVING HAMPTON ROADS NORFOLK - VIRGINIA BEACH - CHESAPEAKE - SUFFOLK - PORTSMOUTH - HAMPTON - NEWPORT NEWS

USE THIS MENU TO LOCATE MORE TIPS FOR EVERYDAY MATH

NOTE: This works for hip and gable roofs.

**Calculating Roof Area from Plans**

- Add the overhang to dimensions.
- Multiply Length by Width.
- Multiply the area by the rafter multiplier that corresponds with the roof slope of your plans.
- Divide by 100 to calculate the number of squares.

**Calculating Common Rafters on Hip / Valley**

- Measure the run (Flat dimension).
- Identify the multiplier that corresponds with the roofs slope.
- Multiply the run by the multiplier.
- Round to the next "even" number.

**RAFTERS**

Example: What is Square Feet in the Gable Area of a 50' wide building with a 12' Gable Height?

- GA = Gable Height x Run ÷ 2
- GA = 12 x 25 ÷ 2
- GA = 150 SF

Example: What is the run of a building that has a 60' run? The Slope is 6:12

- Run = 60 ÷ 2
- Run = 30
- GH = Run x Vertical Rise
- GH = 30 x 6
- GH = 180" (or 15')

Example: What is the run of a building that has a 50' span?

- Run = Span ÷ 2
- Run = 50 ÷ 2
- Run = 25

**Calculating the Gable Area of a Building**

**GA = Gable Height x Run**

**Calculating the Gable Height of a Building**

**GH = Run x Vertical Rise**

**Calculating the Run of a Building**

**Run = Span ÷ 2**

**Gable Calculations**

**Gable Height**

**Coverage Area per Roll of Felt (Underlayment)**

**15# Felt Underlayment 400 SF**- 30# Felt Underlayment 200 SF

**Waste Factors**

**Simple roofs (Gable) ---1 - 5%**- Complex roofs -----------5 - 10%

- Measure Height from the bottom of the roofline to the ridge board.
- Measure the Building Length ( include the overhang )
- Multiply Length by Height for the area.
- Divide total area by 100 ( this is the number of squares required )
- Multiply the squares by the number of bundles per square ( or see the table Below, or manufactures instructions for quantity )

**Calculating Bundles of Roof Covering**