• How to overlap Corrapol Corrugated Roofing Sheets

    How to overlap Corrapol Corrugated Roofing Sheets

    How to overlap Corrapol Corrugated Roofing Sheets


    To install Corrapol Corrugated Roofing Sheets you simply have to overlap your sheets widthways and lengthways and secure them down – easy! This ease of installation is one of the main reasons why corrugated roof sheets are so popular for domestic and commercial projects on a wide range of applications.

    This ‘How to overlap Corrapol Roofing Sheets’ is a mega guide with a video covering all the common questions (and some top tips!) about installing and overlapping corrugated roofing sheets. We manufacture a wide range of corrugated roofing sheets and so this guide is applicable for our corrugated sheets ranges including:

    Our Corrugated Bitumen Roofing Sheets

    • Awnapol Premium Bitumen Corrugated Sheets
    • Corrapol-BT Corrugated Bitumen Roof Sheets

    Our Clear Corrugated Roofing Sheets

    • Corrapol Stormproof Heavy Duty Corrugated Sheets
    • Corrapol PVC DIY Grade Corrugated Sheets
    • Corrapol GRP Corrugated sheets


    Why are corrugated roofing sheets overlapped?

    Creating a waterproof cover is one of the main functions of a roof and so overlapping your corrugated sheets helps to seal the roof properly. It is important to overlap corrugated sheets properly when installing, taking into account your specific roof requirements including the pitch of your roof, location and other factors.

    Overlaps on corrugated roof sheets, such as Corrapol PVC sheets, can be length or widths ways making it simple to calculate how many sheets are required and requiring minimal cuts.

    Which way are corrugated roofing sheets overlapped?

    When installing corrugated roofing sheets, bitumen or plastic, always try to install with the prevailing direction at your location. This is advisable as it reduces the chance of wind uplift over time and increases the life span of the roof.

    If you are unsure about which direction the prevailing wind is at your project location the best way is to simply observe the weather/wind for a few weeks prior to your installation to spot the wind patterns in the area.


    How much should you overlap corrugated roofing sheets? 

    Width Overlaps

    Always overlap corrugated sheets a minimum of one or two corrugation peaks widthways depending on your roof pitch:

    Pitch greater than 10° - One Corrugation overlap
    Pitch less than 10° - Two Corrugation overlaps

    It is also possible to overlap more than two corrugations if you don’t want to trim your sheets at the edge and would prefer to just overlap more over the roof.

    Please see our How to Cut Corrugated Bitumen Sheets Guide for help on how to cut our Corrapol-BT Bitumen Sheets.

    How much should you overlap corrugated roofing sheets?

    Length Overlaps

    For longer roofs then you will need to overlap the corrugated roofing sheets lengthways as well. As with the width overlaps, how much you need to overlap the sheets lengthways depends on the pitch of your roof:

    Pitch of 15 degrees or over - Overlap 180 mm
    Pitch between 10-15 degrees - Overlap 220 mm
    Pitch between 5-10 degrees - Overlap 320 mm


    Why do you need to leave extra space beside corrugated sheets on either side of a roof?

    Before installing your corrugated roofing sheets remember to allow space for your Rock N Lock Flashings. Corrapol Rock N Lock Flashings are manufactured in a gable or wall option to suit if you have an open side or sidewall at your gables. 

    Designed to reduce the chance of wind uplift and protect the gables of roofs from the elements the Rock N Lock is an essential component and needs to be included in any width calculations. Approximately 40mm should be allowed for the Rock N Lock flashing on each side of your corrugated roof.

    If the last sheet corrugation doesn’t end exactly at 40mm out then simply overhang the Rock N Lock over the edge to suit. We suggest installing the first Corrapol Rock N Lock, on one side, to help guide the corrugated sheets across.

    How much do you Overhang Corrugated Roofing Sheets?

    Corrugated sheets need overhung at the bottom edge or gutter of a roof to allow for drainage into your gutter. We suggest a maximum 70mm overhang over the edge of the eaves.

    The best distance to overhang corrugated roofing sheets varies depending on the below. As a guide, the more exposed a roof the less you are best to have as the risk of wind uplift is higher. Also, the steeper the roof pitch the less overhang will be needed to ensure rain water raining doesn’t overshoot the gutter.

    • How exposed is the roof?
    • How steep is the roof?
    • How high does the gutter sit on the eaves?






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