How to Install and Maintain Corrugated Roofing Sheets

Corrugated roofing sheets offer a durable and cost-effective solution for both residential and commercial roofing projects. Whether you build a new structure or replace an existing roof, understanding the benefits, proper installation techniques and maintenance needs of corrugated roofing sheets is important. 

This guide delves into the benefits of using corrugated sheets for roofing, provides step-by-step installation instructions and offers valuable tips for prolonging the lifespan of your corrugated roof. Following the guidelines outlined in this article ensures you achieve a long-lasting and visually appealing roofing solution.

What is a corrugated roofing sheet?

Corrugated roofing sheets are roof coverings made from various materials, including steel, aluminium, plastic and fibre-cement. These sheets feature a distinctive wave-like or ridged corrugation pattern running lengthwise. This enhances the structural strength and rigidity compared to flat sheeting.

The corrugations create alternating parallel grooves and ridges, allowing the sheets to span greater distances while remaining lightweight and easy to install. This unique design distributes weight and stress evenly across the surface. It makes corrugated roofing an ideal choice for withstanding heavy loads including wind, snow and foot traffic.

Corrugated sheets are used for various applications.

• Residential roofing: Used for house, garage, shed or small outbuilding projects where an affordable yet long-lasting roof is needed. 
• Agricultural buildings: Frequently chosen for barns, stables and farm equipment shelters. This is because of their resistance to moisture, chemicals and corrosive environments.
• Industrial/commercial: Provides protective covering for factories, warehouses and large-span structures that require resilient and low-maintenance roofing.
• Shade structures: Translucent heavy duty corrugated plastic roofing sheets allow diffused natural light through for patios and greenhouse coverings.
• Temporary structures: Fast and easy assembly makes corrugated sheets an economical roofing solution for job sites. 

What are the different corrugated roof sheet types?

Corrugated roofing sheets are available in a variety of materials, each with its own unique set of properties. The material you choose will depend on factors such as durability needs. Below are the common corrugated roof sheet types to consider.

1. Galvanised steel

Galvanised steel is one of the most commonly used materials for corrugated roofing sheets. These sheets are made from steel that has been coated with a thin layer of zinc to prevent rusting and corrosion. 

The zinc coating is applied through a hot-dip process or electroplating. Corrugated galvanised roofing sheets typically range in thickness from 22-30 gauge (0.6 - 0.3mm). They are highly durable and can last 30-50 years with proper maintenance. 

Plus, they are fire-resistant and do not easily burn or melt. Galvanised steel offers a good strength-to-weight ratio, allowing it to span longer distances. However, if a thin gauge is used, these sheets may dent from hail or falling objects. 

2. Aluminium 

Aluminium corrugated roofing sheets are made from aluminium alloy coils that are roll-formed. They are very lightweight, weighing only about one-third as much as steel. Aluminium is extremely corrosion-resistant due to a naturally occurring oxidation layer that forms on its surface. It does not rust, rot or combust, making it a highly durable option. 

Aluminium also offers high thermal and electrical resistance properties. Its reflective surface can help reduce cooling costs by reflecting radiant heat. Aluminium is more malleable and less likely to crack or shatter than steel. These corrugated sheets have an estimated lifespan of 40-60 years.

3. Polycarbonate

Polycarbonate corrugated roofing sheets are made from a rigid thermoplastic polymer material. They are translucent, allowing 80-90% of light to pass through. Plus, polycarbonate is extremely impact-resistant. It offers excellent insulation value with high thermal resistance. 

UV-protected versions resist discolouration and brittleness over time. Polycarbonate is also very lightweight, weighing only about one-sixth as much as glass. More flexible than rigid plastics, polycarbonate can span longer distances. However, it does scratch relatively easily and requires special cleaning products.

4. Bitumen

Bitumen corrugated sheets are made from fibre materials like cellulose or glass. They have been saturated with bitumen, a sticky, semi-solid residual oil byproduct. These sheets offer good water resistance and function as an effective moisture barrier. They also provide decent insulation properties. 

A main benefit of corrugated bitumen roofing sheets is their affordability. However, they are quite heavy and require sturdy structural support. Bitumen sheets also have a relatively limited lifespan of just 10-20 years before deterioration sets in.

5. PVC

Corrugated sheets made from rigid polyvinyl chloride (PVC) plastic offer superior resistance to moisture, fire and weathering. Their smooth surface is easy to keep clean and requires minimal maintenance. PVC retains its colour well over an extended period. 

While rigid, PVC corrugated roofing sheets are still relatively lightweight compared to other materials. They also provide good thermal insulation properties. The main downside is a higher upfront cost than metal roofing sheets. 

After years of UV exposure, clear corrugated roofing sheets can potentially become brittle. 

6. Fibre-cement

There are two main types of fibre-cement sheets. Corrugated cement roofing sheets are made from a mixture of cement and wood or cellulose fibres. They have a grey, concrete-like appearance and are suited for agricultural buildings and industrial uses.

Corrugated concrete roofing sheets contain a higher proportion of concrete combined with fibres for maximum strength. They are heavier than cement sheets with a rougher concrete texture and are primarily used for industrial and large roofing projects.

Both are incredibly durable and long-lasting with an average lifespan of 30-50 years. They are resistant to rotting, fire, insects and moisture damage. Also, they both hold good insulation properties with low thermal conductivity. 

How to install corrugated roof sheets

Installing corrugated roofing sheets requires careful preparation and the right tools. Properly securing the sheets and accounting for thermal expansion is crucial for a weathertight roof. Having the right materials on hand will ensure an efficient installation process.

Step 1 - Gather tools and materials

Step 2 - Prepare the roof deck

Start by properly preparing the roof deck surface. Make sure it is clean, smooth and free of any protruding objects that could puncture the underlayment. Install an asphalt-saturated felt paper underlayment to provide an extra moisture barrier underneath the corrugated sheets.

Step 3 - Determine sheet overlap

Next, determine the appropriate sheet overlap based on the manufacturer's recommendations. Typically, sheets should overlap by 1-2 corrugations on the sides and 100mm - 150mm (4-6 inches) at the end laps. This allows sufficient room for expansion and contraction of the sheets as temperatures fluctuate.

Step 4 - Lay the first sheet

When installing the first corrugated sheet, start at one side of the roof, securing it at every other corrugation crest using fasteners compatible with that material. For steel, use galvanised or stainless steel screws with washers. 

For aluminium, fasteners must be used to avoid corrosion. Pre-drill holes when installing polycarbonate and PVC to prevent cracking. Also, be sure to space fasteners 150mm - 300mm (6-12 inches) apart.

Step 5 - Properly overlap sheets

As you install subsequent sheets, stagger the end lap joints so no two vertical joints are inline. This creates a stronger, more secure roof system. Seal all laps with sealant tape or roofing caulk designed for that specific sheet material. 

For bitumen sheets, make sure to offset the side laps from the end laps and fasten through pre-punched holes only.

Step 6 - Install trim and flashing

Allow for adequate overhang at the eave and rake edges as specified by local building codes, typically 25mm - 50mm (1-2 inches). Install closures, transition pieces, ridge caps and flashing using components to prevent corrosion or other damage.

Step 7 - Expansion and ventilation

Accommodate thermal expansion and contraction by ensuring fasteners are properly spaced as directed. With certain materials like steel and polycarbonate, make sure to create sufficient ventilation to prevent excessive heat buildup and buckling.

How much maintenance does corrugated roofing need?

While corrugated roofing is known for its durability, proper care and upkeep are still essential. Neglecting maintenance can lead to premature deterioration and shorten the roof's lifespan. Here are some general tips to follow.

Galvanised steel

• Inspect yearly for scratches, dents or rust spots. Areas with rust should be sanded down to remove flaking. They should also be treated with a rust converter product to stabilise, and then covered with a zinc-rich primer and rust-resistant coating.
• Every 5-10 years, thoroughly clean the whole roof surface using a mild detergent and rinse to remove built-up grime, chalk, and oxidation. Allow to fully dry before applying a new protective coating specifically for corrugated metal roofing sheets.
• Clear debris from corrugation channels regularly to allow proper drainage and prevent damming of water which can accelerate rusting.

Aluminium

• Check yearly for chalking (white powder residue), fading of colour or corrosion caused by direct contact with dissimilar metals like steel fasteners/flashing. 
• Clean every 2-3 years using a mild detergent and a soft brush or cloth to remove accumulated oxidation, dirt, and contaminants that can cause staining.
• No need for repainting or application of protective coatings. Aluminium types like corrugated tin roof sheets have a natural oxide layer to protect against corrosion.

Polycarbonate

• Clean annually using only cleaners specifically approved for polycarbonate to avoid scratching the surface.
• Use a pole with a soft brush attachment to gently scrub hard-to-reach areas and dislodge stuck-on grime.
• Check sealants around lap joints, fastener points, and flashing connections periodically for any cracking, separations or degradation and re-seal as needed.
• UV-protected sheets may require re-application of a UV-resistant coating or replacement every 5-10 years as the UV protection wears off.

Bitumen

• Inspect every 6 months for any cracking, brittleness, curling edges or other degradation of the bitumen coating.
• Remove any debris, moss or fungus growth immediately by hand or gentle brushing to prevent further spreading.
• Reapply bitumen-based aluminium coatings or emulsions every 3-5 years to saturate dried areas and restore waterproofing.
• Consider full roof replacement after 15-20 years as bitumen becomes increasingly brittle and vulnerable to leaks.

PVC

• Check yearly for any signs of impact damage, holes, cracks or tears in the sheets.
• Clean every 1-2 years using just a mild soap and a soft bristle brush or cloth. Avoid harsh chemicals, abrasives or pressure washing that can scratch or dull the surface.
• Reseal all lap joints, fastener points and flashing details every 5-7 years using PVC-safe sealant products to maintain a weathertight seal.
• Repair cracks or holes in corrugated plastic roofing sheets promptly by applying a compatible PVC repair tape or sealant.

Fibre-cement

• Inspect annually for any cracks, holes, or damaged sheets and replace them as needed.
• Clean every 2-3 years by hosing off dirt or debris or pressure washing
• Use only mild detergent if needed and be sure to avoid harsh chemicals.
• Check sealants around joints/fasteners and re-caulk if deteriorating.
• Look for any vegetation growth trapped in corrugations and remove it.