# How do you calculate the effective area of a roof?

Contents

The roof area (RA) is calculated easily: We multiply the Roof Length (c) (which is the sum of building length plus the gable end overhangs of the roof) by the Roof Width of slope (a) that we just figured out above when we computed the hypotenuse of the roof triangle (that’s why we needed the roof rise number).

## How do you calculate the area of a roof?

Multiply your house length by your house width to get the area. (For example, 40 feet x 30 feet = 1,200 square feet.) Next, multiply the area by your roof’s pitch. (1,200 x 1.05 = 1,260 square feet.)

## What is effective roof area?

To calculate the Effective Roof Area you should use this formula: Roof Length X Half Roof Width X Roof Height ÷ 2 = Roof Area. Calculate the area of a roof to work out how much guttering is required.

## What is the most common roof pitch?

The most commonly used roof pitches fall in a range between 4/12 and 9/12. Pitches lower than 4/12 have a slight angle, and they are defined as low-slope roofs. Pitches of less than 2/12 are considered flat roofs, even though they may be very slightly angled.

## How many squares are in a 1200 square foot roof?

To determine the number of squares on the gable roof above, divide its total of 24,000 square feet by 100 (24,000 ÷ 100 = 240).

How many shingles do I need for 1000 square feet?

House by Square Foot Roof by Square Foot Re-Roofing Cost*
1,000 1,054 \$4,000 – \$5,500
1,100 1,160 \$4,200 – \$6,000
1,200 1,265 \$4,500 – \$6,500
1,500 1,581 \$5,500 – \$8,000

## How much roofing area does a downspout need?

Plumbing codes typically use the vertically projected roof area for drainage design and they often use a square foot allowance per square inch of downspout for 1 in./hr. (25 mm/hr) rainfall that varies with diameter, for example, 3 in.

## What is the pitch of a roof?

Roof pitch (or slope) tells you how many inches the roof rises for every 12 inches in depth. An Example of a roof pitch would be a “6/12 pitch” which means that the roof rises 6 ” for every 12″ inward towards the peak (or ridge). There are two suggested ways to measure a roof pitch.

## How much of my roof is flat?

From an insurance point of view, most companies consider a roof to be flat if it – or more than 25% of it – slopes less than 10 degrees. That’s why you’ll often be asked how much of your roof is flat when applying for a flat roof insurance policy.

## What roof pitch is 30 degrees?

What roof pitch is 30 degrees? A 30° roof pitch is roughly the same as a 7/12 roof pitch. To convert from degrees to the American ratio: Find the tangent of the angle, tan(angle).

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## What is a 4/12 pitch?

A roof that rises 4 inches for every 1 foot or 12 inches of run is said to have a “4 in 12” slope. … The slope ratio represents a certain amount of vertical rise for every 12 inches of horizontal run. For example, a “4 in 12” slope can be expressed as the ratio of 4:12. A “6 in 12” slope is expressed as 6:12.

## What degrees is a 3/12 pitch?

What degree is a 3/12 pitch roof?

Roof Pitch (slope) Roof Angle (degree)
3:12 Pitch 14.04°
4:12 Pitch 18.43°
5:12 Pitch 22.62°
6:12 Pitch 26.57°

## How many squares is a 1000 sq ft roof?

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Conversions Table
10 Square Feet to Roofing Squares = 0.1 800 Square Feet to Roofing Squares = 8
20 Square Feet to Roofing Squares = 0.2 900 Square Feet to Roofing Squares = 9
30 Square Feet to Roofing Squares = 0.3 1,000 Square Feet to Roofing Squares = 10

## How many bundles of shingles does it take to cover 1200 square feet?

How many bundles of shingles do I need for 1200 square feet? The average bundle of shingles covers 33.3 ft2, so three bundles of shingles are needed per square.

## How many squares is 3000 square feet?

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Conversions Table
10 Roofing Squares to Square Feet = 1000 800 Roofing Squares to Square Feet = 80000
20 Roofing Squares to Square Feet = 2000 900 Roofing Squares to Square Feet = 90000
30 Roofing Squares to Square Feet = 3000 1,000 Roofing Squares to Square Feet = 100000
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