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Measuring your roof

Measurements required to specify roofing sheets will differ depending on the type of roof you have. Below we have listed more detailed measuring instructions for the most common types of roofs we encounter. If you are unsure of your roof type please contact our technical team for help.

Common roof types

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Mono pitch roofs are very common in garages and car ports. Sometimes the width of a mono pitch roof is more than the length of the sheets required. The examples below gives guidance on the measurements that should be taken to correctly specify your roofing sheets.

mono pitch (single slope roof)

Mono pitch roofs are usually the easiest to measure. A width measurement is required to calculate the number of sheets. The length measurement is required to calculate the length of sheets. Flashings can be used at the ridge end and sides if required. The types of flashing can differ depending on situation.

Apex roofs are usually even sided but can be uneven (sheet lengths will differ from one side to the other). The diagram below gives guidance on the measurements that should be taken to correctly specify your roofing sheets.

apex (double slope roof)

The ridge length is used to calculate the number of sheets required for each side. The ridge to eaves measurement is used to calculate the sheet lengths. If the apex is uneven ridge to eaves measurements will need to be taken on both sides.

Adjoining apex roofs incorporate more than one apex roof connected to each other. Measurements on these roofs need to be taken a little differently from an ordinary apex roof. Sheets will need to be cut on site where the roofs join and valley or hip flashing should be fitted at the joins. The following examples give guidance on the measurements that should be taken to correctly specify your roofing sheets.

Example 1 T-shaped

The below example is a common form of an adjoining apex roof commonly known as T-shaped. The joins form two valleys which will require flashing.

t-shaped apex roof

Measurements are essentially taken as two roofs (indicated above in blue and green)

To calculate the sheets required for the main apex (blue) ridge line 1 must be taken to calculate the number of sheets required whilst ridge to eaves 1 and 2 are used for the sheet lengths each side of the apex.

The process is then repeated for apex 2 (green) using ridge line 2 and ridge to eaves 3 and 4.

Sheets are cut down on site to create the valleys. Two piece valley gutter flashings are recommended to divert water away and provide a neat finish where sheets meet at the valley. Ridge flashings are used at the ridge lines (tip of the apex). Bargeboards can be used along the gable ends.

Example 2 L-shaped

l-shaped apex roof

The above example is slightly more complex than the T-shaped roof and should essentially be treated as four separate areas.

To calculate sheets requirements measurements must be taken along ridge line 1 and ridge to eaves 1. This process should then be repeated for ridge line 2 and ridge to eaves 2. This will give you sheet size specification for the inside section of the L-shaped roof (green and orange areas)

You can then move onto the outside section (blue and purple) Measurements should be taken from gutter line 3 and ridge to eaves 3 followed by gutter line 4 and ridge to eaves 4.

The above example forms a valley on the inside and a hip on the outside. Two piece valley flashings and hip flashings should be used where sheets meet at the valley and hip. Ridge flashings are used at the ridge line (tip of the apex). Bargeboards can be used along the gable ends.

Hipped roofs will require cladding at the gable ends as well as the two sides of the apex. This will mean that four areas will require cladding. Measurements on these roofs need to be taken a little differently from an ordinary apex roof. Sheets will need to be cut on site where each cladded area meets and hip flashing should be fitted at these joins. The diagram below gives guidance on the measurements that should be taken to correctly specify your roofing sheets.

hipped roof

Hipped roofs require four sections of cladding (indicated above as blue, green, purple and orange areas). Measurements must be taken along the gutter line for all four sections as well as ridge to eaves.

Hip flashings should be used where sheets meet. The amount of hip flashing is calculated by measuring each separate hip join.

Ridge flashings are used at the ridge line (tip of the apex). The amount of ridge flashing is calculated by measuring the ridge line.

quick tip - measuring