Roofing: Calculate the Number of Shingles

What You'll Need
Measuring Tape
Pen and Paper

Roofing is a very important part of your house because it protects it from water. Without a watertight room water would be allowed to enter and stream down the walls in your house. It's essential that the roof is in the very best condition.

Pitched roofs are commonly weatherproofed by using shingles, and these are arranged so that they overlap one another. It's important that  you have the right number of shingles on your roof, because if you have too few then it won't be waterproof. You will then need to go back to the store a second time to buy more. Ordering too many roofing shingles will waste money.

There are a number of calculations that you can use to work out exactly how many shingles you need to correctly cover your roof. These calculations aren't scary because you don't need to worry about anything you learned in school.

Step 1 - Calculating the Square Footage

The first thing that you will need to do is work out the size of your roof in square feet. This is very easy, as it's simply a matter of measuring the length and height of the room. Multiply the length and height of the roof together to work out the number of square feet that you need to cover. Remember to work out the total square footage around the whole of your house. For a simple room this will be very easy. However for larger, more complicated shapes you will need to work slowly.

Step 2 - Working out Number of Squares

Work out the number of squares on your room by dividing the square footage of your roof by 100. This figure is very important and should be written down on a piece of paper. Mark this down as the number of squares.

Step 3 - Work out Number of Bundles

Each square on your roof will need three bundles of tiles to be filled properly and waterproofed. To work this out, simply multiply the answer you got from step 2 by 3. This will give you the number of bundles that you need to purchase.

Step 4 - Allowing for Eaves, Mistakes and Difficulties

The number you calculated in step 3 is the exact number of bundles that you need to purchase to complete the roofing project. However, this does not give you any margin for error. Roof tiles are very delicate and can be damaged easily. Also, working out the number of tiles around bay windows or eaves can be very difficult.

You include 10-20% extra tiles to allow for any broken or damaged tiles. This also makes it much easier to tile around all of the parts of your roof.