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How To Install Corrugated Roofing Sheets

How To Install Corrugated Roofing Sheets
Corrugated roofing sheets can make all the difference in construction or DIY projects. Perhaps as a roof for your garden shed, a waterproof shelter over a patio, or even on a larger scale in agricultural buildings, corrugated roofs are a practical and timeless staple.

Many people struggle to install them themselves – mostly due to unfamiliarity. But there’s no need to fear, a core purpose of corrugated roofing is to make installation a whole lot easier! What do you need to install a corrugated roof?

While felt roofing itself requires several complex tools, when installing corrugated roofs, you’ll only need the basics:

• Protective eyewear and gloves
• Roofing sheets of the right length, finish, and colour
• A suitable drill bit and screws with washers
• Ladder
• Tape measure
• Soft wooden block & mallet
• Rag

How To Choose The Best Roofing Material

First, it is essential that you pick the right roofing sheet for the job. Here at Colour Clad Profiles, we offer both corrugated roofing sheets and roofing lights in all manner of finishes, colours, sizes, and shapes.

To be clear from the get-go, make sure you know what you want to get out of your corrugated roof. If you’re looking for sheer watertight, durable protection, you might want to consider a galvanised roofing sheet. If you are looking to add light to the roof of your structure, translucent plastic corrugated sheets are your best bet.

From here, you’ll need to decide which finish and colour you’d like. You can choose from the following finishes:

• Anticon
• Plain galvanised
• Plastisol-coated (PVC)
• Polyester coated

Each finish has its own range of unique properties that are best suited to certain jobs. Plain and galvanised sheets are extremely weather-resistant and hard-wearing, making them well-suited to agricultural buildings like barns. PVC-coated roofing sheets, on the other hand, are often used to clad residential buildings.

As for colours, most reputable roofing sheet retailers will stock a standard range of colours that are often used for roofs. You can download our colour chart here.

Measuring Your Roof

To avoid any mistakes, it’s essential that you measure your roof accurately. This is because sheets usually come pre-cut as 1m widths – so you’ll want to know what width of roof you’ll need to cover in order to order the right amount.

You will need to account for some overlap between the sheets – as well as enough of an overhang to help channel water away from the sides of whatever structure you’re covering. But to stop you having to do complex calculations, our sheets come oversized so that the total actual coverage when side lapped is 1 metre.

All you’ll need to do, then, once you’ve measured your roof, is select the thickness of sheets you need, then put in the length of the sheets needed (this will be the length from the roof’s ridge to the eaves) and the number of sheets you’ll need to cover the total width of your roof. Don’t forget to double this for a normal centre-pitched roof! You wouldn’t believe the number of times we’ve received orders for half a roof!

Drill Your Holes

Some corrugated roofing sheets come with pre-drilled holes. If yours don’t, not to worry, it is an easy task when you know how. For aesthetic and accuracy-related purposes, err on the slimmer side when it comes to drill bits so that the screws can create a snug fit – you don’t want to accidentally over-size holes with metal sheets.

Spacing-wise, the holes on the ends and sides of the panels should have a gap of 15-20cm between them. This should line up with the rafters, but you’d be well advised to get a few sheets on the roof and mark them before drilling any holes.

To get the holes accurate, you can mark the positions with a marker, then use an awl to hammer a small dent on each marker – this should stop the drill bit from slipping around when you’re starting the hole.

When drilling and cutting, wear eye protection, especially if dealing with galvanised steel roofing sheets. Gloves are also advised since the freshly cut edges of these sheets can be surprisingly sharp.

Install Corrugated Roofing Sheets

In order to install the corrugated roofing sheets once drilled, you’ll need to place them onto the rafters – parallel with the rafters (so that the long side is in the same direction). To make it easier for yourself, begin on the outside edge or corner, facing away from the prevailing wind direction so that any oncoming wind doesn’t keep flipping the sheet up. If it’s especially windy then you’re usually better off waiting for it to die down – a strong gust can make a metal sheet quite dangerous quite quickly.

To improve the performance of the roof in the long run, it is wise to seal off the ends with another piece of wood or a plastic strip – and usually some sort of flexible sealant like polyurethane. This is to prevent water, drafts, or insects from getting in.

When laying your first few sheets down, don’t fully fix them into place until you are sure they are aligned correctly and laying flush. If it is a single-pitch roof you are working on, we recommend 10 degrees as the minimum pitch angle. The first row of sheets should create an overhang for rainwater to drain from by extending over the bottom purlin.

For the overlapping aspect, the corrugated roof sheets should have at least one corrugation acting as a ‘side lap’ underneath or on top of the corrugation of the adjacent sheet. These laps can be secured with lapping tape – which should help protect them from rain ingress and from being blown upwards and rattling in the wind.

Once you are sure of the positioning of the sheet, tap each sheet into place tightly before screwing them down. In order to get the tightest fit (without damaging the sheets), use a soft wood block and a mallet to do this – taking care to place a rag between the wood and the sheet.

To attach the sheets to the rafters, use appropriate-length screws with polycarbonate washers. The screws need to be long enough to hold the sheets firm and need to be quite weather resistant in order to avoid having to replace them every few years. Stainless steel screws can be perfect for this, but they can also be a little more brittle than other types of metal so if you’re roofing somewhere that gets a lot of wind then it’s best to check first.

The polycarbonate washers should help to keep the holes watertight – just make sure you get ones that are UV resistant and that you’re using dome-head screws, so they pull tightly against the washers. Additionally, if you’re wanting the roof to stay up, if possible, it’s quite common to squeeze a little polyurethane glue sealant into each hole before driving the screws.

Make sure you get sealant that’s UV resistant and rated for external use. CT1-branded sealant is the perfect sealant for a permanent job. Many DIYers sheeting, for example, a small shed or an out-house will opt for a bathroom silicone simply because that’s the most visible in DIY shops.

Buy Corrugated Roofing Sheets

When it comes to covering a roof, make sure you’ve got yourself covered with the best quality roofing materials. If you need any advice on your order, give us a call and we’d be happy to help. Get In Touch
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