Calculating Ridge Height and Rafters

This video tutorial explains how to calculate the height of a ridge board for a common rafter roof. It covers the basics of a 9/12 pitch roof, the importance of the measuring line, and key considerations for rafters and ridge boards. The tutorial provides a step-by-step guide to calculating the theoretical ridge height and the height above plate, using specific measurements and equations. It concludes with a summary of the process and encourages viewers to ask questions if needed.

What is the purpose of today's video?

• To learn how to calculate the height of a ridge board for a common rafter roof

• To understand the basics of carpentry

• To learn how to install a roof

• To calculate the length of a rafter

What does a 9/12 common rafter roof mean?

• The roof has a span of 12 feet and a run of 9 feet

• The roof has a span of 9 feet and a run of 12 feet

• The roof rises 12 inches for every 9 inches of horizontal run

• The roof rises 9 inches for every 12 inches of horizontal run

What is the total run of a roof with an overall span of 4 feet?

• 2 feet

• 4 feet

• 6 feet

• 8 feet

Why is it important to sight down all rafter and ridge material?

• To ensure the wood is dry

• To check for any cracks

• To measure the length accurately

• To ensure the crown is facing up

What is the recommended size for a ridge board if the rafters are 2 by 6?

• 2 by 8, 10, or 12

• 2 by 4

• 2 by 2

• 2 by 6

What is the measuring line used for?

• To base all initial math calculations

• To measure the length of the rafter

• To determine the width of the ridge board

• To mark the bird's mouth cut

What is the formula to find the theoretical ridge height?

• F = B * D / 12

• F = B + D / 12

• F = B - D / 12

• F = B / D * 12

How do you calculate the total ridge height?

• By multiplying the unit rise by the total run

• By subtracting the ridge thickness from the total run

• By adding the theoretical ridge height and the height above plate

• By dividing the total run by the unit rise

What is the height above plate?

• The distance from the bottom of the plate to the bottom of the rafter

• The distance from the top of the plate to the bottom of the rafter

• The distance from the bottom of the plate to the top of the rafter

• The distance from the top of the plate to the top of the rafter

What four things do you need to know to calculate the total ridge height?

• Ridge thickness, total run, unit rise, and rafter length

• Ridge thickness, total run minus ridge thickness, unit rise, and height above plate

• Ridge thickness, total run, unit rise, and overhang length

• Ridge thickness, total run, unit rise, and bird's mouth cut