How to Overlap Corrugated Metal Roofing

overlapping corrugated metal roofing sheets

Corrugated metal sheets are one of the smartest choices when it comes to effective roofing solutions. They are not only fire-resistant but easy to work with and install as well. A critical aspect of corrugated metal roofing, however, is making sure it is watertight. In this article we will cover the proper steps for ensuring quality overlapping and installation.

Dress for safety 

Before you even begin the installation of corrugated metal roofing, you must consider safety. In particular, this means making sure you are dressed in a way that is appropriate for the task at hand. After all, corrugated metal roofing has several important benefits, but it is also a product that can pose a risk of cutting those working with it.

With that in mind, you and anyone else working with you must wear the right protective clothing such as safety goggles that will protect the delicate eye area from stray shards of metal and debris. Robust work gloves will do the same job for your hands, which are at particular risk of being cut or scraped when working with metal sheeting. You may even wish to use earplugs when working with power tools, as over an extended period they can cause damage to their operators’ hearing. 

Plan your project thoroughly 

One of the worst mistakes you can make when working with corrugated metal is to get started without carefully considering each step of the task in front of you. For example, you do not want to have to measure or trim the metal sheets while up on the roof, instead, this work needs to be completed before you begin the installation phase. 

The good news is that most sheets won’t need to be altered or trimmed at all. In fact, it is only the gables or roof edges where alterations will need to be made. Although it is also possible to use a ridge cap in these areas as well. 

Such alterations are particularly important because they provide a customized fit for the roof on which you are working, something that will prevent any water from leaking through and compromising the roof’s structure. 

However, if you do need to cut corrugated metal roofing sheets be sure that you carefully measure them beforehand. Then when you are ready to make the cut choose nibblers, or electric shears for the task, unless it is particularly small and then tin snips may do the job. 

The installation of metal siding

In addition to roofing, corrugated metal sheets are also ideal for use as metal siding. However, the process of installing corrugated metal sheets on the side of a building is a little different than the process for roofs. 

In fact, aside from the safety suggestions above, you will need to begin metal siding work in a particular place. Usually, this is the opposite of the direction that the rain and wind come from as this helps to create a tighter, more effective weatherproof seal. 

Before installing metal siding you will need to work out the directions in which the panels will be overlapped. Remember it is the overlap that prevents water from getting in, so it needs to be right! 

The good news is you should be able to tell which end of the panel is designed for overlap and which is for underlap pretty easily. This is because the overlap parts stick up, while the underlap part is situated lower. As you install each panel make sure that the overlapping ridge sits directly over the underlap of the previous panel.

Fastening and sealing the panels 

You probably have a good idea that ensuring the panels are watertight and secure are some of the most important things when working with corrugated metal. Indeed, their whole design revolves around these factors. However, that doesn’t mean that correct fastening and sealing don’t also play an important role. 

In fact, if the slope of the roof you are working on is 2:12 or less it is vital to use sealant on the overlapping parts of the sheeting. 

Fortunately, applying sealant is a pretty easy task, as all you need to do is apply a line all the way down the length of the underlap ridge. Then as you place the overlapping ridge in position the sealant will help glue both pieces together and offer protection against water getting into the joint. 

After sealing, you can apply screw fasteners. These should be 1-1.5 inch screws with waterproof washers at the head. Often neoprene or rubber washers are used. Install these screw fasteners with an electric drill with a screwdriver tip in rows of three. The first two should be on each side of the overlay underlay ride, while the third should be directly placed through the ridge itself. Repeat this down the entire overlap joint every 6 inches to complete the task. 

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