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Tips On Overlapping Your Metal Roofing

One of the most common mistakes people make when installing metal roofing sheets is not overlapping the sheets correctly.

Overlapping the sheets allows the water to flow down the roof without damaging the structure of the building underneath. The amount of overlap you need depends on the slope of the roof you are fitting.

There are different methods of overlapping metal roofing sheets, but they should be overlapped via the lengths or ends of the sheet and secured correctly to avoid damage and allow them to last. The ease of fitting corrugated roofing sheets is one of the reasons they are so popular. However, some people find there are mistakes made when fitting them that lead to leaks or breakage later in their roof life. This is why we’re sharing our tips for overlapping your metal roof.

Include Overlaps in Your Roof Area Measurements

One of the most common mistakes is forgetting to consider the overlap when measuring your roof for sheets. The overlap measurement will depend a lot on the pitch of your roof, which we will talk about later.

You will also need to think about which overlaps you require. You should always overlap the width of your metal roof sheet, but in some instances, you will also need to overlap the length.

By considering how much overlap you require, you can avoid not having enough sheets to cover your entire roof area.

Corrugated roof sheets stacked in warehouse

Overlap the Higher Sheet

As a general rule, you should aim to overlap the higher sheet of roofing, as this will aid water flow down the pitch of your roof. Therefore, you start at the bottom of the rooftop, and work your way up. This will allow an underlay edge at the top of the first sheet you put in place.

Enjoy Stronger Seams With Lengthwise Overlapping

Longer roofs will require a length overlap in addition to the width. This helps give your roof stronger seems and protects the structure from damage.

How Much Overlap Is Needed From Metal Roofing Sheets?

As mentioned, the amount of overlap you require depends on the pitch of your roof. The amount of overlap required is also different if you are overlapping the widths or the lengths.

Width Overlap

You should always overlap your metal sheets by a minimum of one corrugation peak. We recommend that a pitch more significant than 10 degrees has a one corrugation overlap, and those with a slope less than 10 degrees have an overlap or two.

Length Overlap

Length overlap is measured in millimetres. Again, this depends on the pitch of your roof. We would suggest:

  • A pitch between 5 and 10 degrees: overlap of 320mm
  • A pitch between 10 and 15 degrees – overlap of 220mm
  • A Pitch 15 degrees or more – overlap of 180mm

metal tile effect roof sheets on building

Consider the Wind Direction

You want to ensure that you install away from the direction of the prevailing wind with self-built constructs such as summer houses and lean-tos. When installing, you will start at the eaves. This means the edges of the sheets aren’t facing into the wind and will be protected more. If you don’t know which direction the prevailing wind is, spend a few weeks at your location and gauge it from there. Generally, the wind direction in the UK sits between west and south, but factors around the site where you are roofing may adjust this.

How to Lay Corrugated Roof Sheets

How to Secure Your Overlap

When overlapping corrugated or box profile roof sheets, you should always use lapping tape or sealant on the widthways edges and both lapping tape and stitching screws on the lengthways edges. This helps ensure you get a robust weatherproof seal on the overlap.

Place your sheet stitching screws at 600mm intervals down the side lap to assist the bond from the tape.

Make Sure You Use the Right Tools

Not only should you use the right tools, but you should ensure you are dressed correctly for the job. It’s imperative to wear thick gloves to stop you from cutting yourself on the edges when overlapping sheets, and you should also keep safety goggles on and a pair of earplugs nearby if your sheets require cutting.

You’ll also want to pre-drill your holes if the metal roofing sheets you purchased don’t have them in place. Ensure you have the correct drill and bit to enable you to do this.

Additional Tips for Installing Metal Roofing

Finally, one of the most important tips for installing and overlapping metal roofing sheets is to consider the weather.

You mustn’t try and install your roof during a storm when thunder and lightning are present or during exceptionally windy days. Not only do you run the risk of damaging your roofing sheets, but you could also cause injury to yourself.

How Bushbury Cladding Can Help With Your Metal Roofing Sheet Installation

Our handy installation guides are available for more information on how to install box profile roofing sheets, corrugated roofing sheets, tile effect sheets, wave effect sheets and steel roofing sheets.

If you are looking for metal roofing sheets for your next project, speak to our team. We have everything from corrugated, box profile and insulated roofing sheets and can deliver across the UK. Speak to our team or shop online today.