Roofing Sheets

What Are Roofing Sheets? 

Roofing sheets are durable panels used to cover a building's roof, protecting it from water, wind, snow, and temperature extremes. These sheets are essential for maintaining the structural integrity of a building, preventing leaks, and ensuring energy efficiency.

When installed, roofing sheets are laid horizontally or vertically, starting from the eaves (bottom edge of the roof) and working upward toward the ridge (the peak). Each sheet overlaps the next by a few inches to prevent leaks, and they are secured to the roof frame (rafters or purlins) using screws, nails, or clips with sealing washers to ensure watertight fastening. At joints, valleys, and edges, flashing strips or sealants are added for extra protection against wind and rain. 

These sheets come in different profiles, such as flat sheets with a smooth surface or profiled sheets with raised ridges or corrugations that offer enhanced strength, water drainage, and wind resistance. Depending on the material, they can also offer additional benefits, such as light transmission (in the case of polycarbonate sheets). 

Applications

• Residential Uses: Garden sheds, carports, and garages.
• Commercial and Agricultural: Warehouses, barns, and greenhouses.
• Conservatories and Extensions: Polycarbonate sheets are particularly popular for conservatories or patios, where both light and durability are needed.

Benefits

• Weather Resistance: Designed to endure a variety of weather conditions, roofing sheets provide protection against rain, wind, snow, and UV rays.
• Ease of Installation: Both PVC and polycarbonate roofing sheets are lightweight and easy to handle, making installation quicker and less labor-intensive.
• Longevity: With minimal maintenance, they offer long-lasting performance, saving you money on repairs and replacements.
• Energy Efficiency: Polycarbonate roofing sheets, in particular, can help reduce the need for artificial lighting during the day, contributing to better energy efficiency in buildings.

Types of Roofing Sheets and Their Benefits

Roofing sheets come in a variety of profiles and materials, each with distinct benefits to meet specific needs:

• Flat Roofing Sheets: These sheets have a smooth, uniform surface, often used for low-pitch or flat roofs. They offer a modern, minimalist look, and are easy to install. They’re ideal for applications such as canopies, verandas, or garden sheds, where the aesthetic and low-maintenance features are key.
• Profiled Roofing Sheets: Featuring raised ridges or corrugations, profiled sheets provide increased strength and rigidity, making them perfect for roofs with a steeper pitch or those exposed to harsher weather. The raised design also enhances water drainage, reducing the likelihood of pooling or water damage. These sheets are typically used in industrial, commercial, and agricultural applications where structural integrity and long-term durability are paramount.

Material Options

• Polycarbonate Roofing Sheets: Known for their high impact resistance, light transmission, and UV protection, polycarbonate sheets are often used in greenhouses, conservatories, and skylights, where natural light is essential. They are also lightweight and easy to install, making them a popular choice for DIY projects.
• PVC Roofing Sheets: These sheets are lightweight, easy to handle, and provide weather resistance at an affordable price point. PVC sheets are commonly used for smaller structures like sheds, carports, or workshops. They are an excellent option for budget-conscious projects.
  
  

How to Choose the Right Roofing Sheet

• Climate: If you live in an area with heavy rainfall, snow, or high winds, you may want to choose a material that can withstand these conditions. Polycarbonate might be ideal in sunnier climates due to its UV-resistant properties.
• Aesthetic Preferences: The type of roofing sheet you choose will affect the overall look of your building. Flat sheets provide a sleek, contemporary appearance, while profiled sheets offer a more traditional, industrial aesthetic.
• Functionality: If your roof needs to allow for natural light, polycarbonate or PVC sheets are excellent choices, offering light diffusion without compromising durability.
• Budget: Consider the initial cost of the roofing sheets, as well as their long-term performance. PVC roofing sheets are typically more cost-effective but may not last as long as polycarbonate options.

Installing Roofing Sheets

When installing roofing sheets, the process involves a few key steps to ensure a secure, durable, and weather-resistant roof. Here’s a more detailed look at how roofing sheets are typically installed:

Preparation of the Roof Deck

Before installation begins, the roof deck (the underlying wooden or metal structure) must be properly prepared. This includes ensuring the surface is clean, level, and free from debris. The roof deck should also be treated to prevent moisture damage and ensure a secure bond with the roofing sheets.

Starting with the First Row

For both flat and profiled roofing sheets, installation starts at the eaves (the lowest edge of the roof) and works upwards towards the ridge (the highest point of the roof). The first sheet is laid along the eaves, ensuring it is properly aligned and level. The edge of the sheet is usually fitted with a drip edge or eaves filler to guide water runoff and prevent moisture from seeping under the sheets.

Laying Successive Sheets

Subsequent sheets are installed, overlapping the one below by a recommended distance (typically around 100mm for metal and profiled sheets) to ensure complete weatherproofing. Profiled sheets require more careful alignment to ensure that the ridges and valleys line up properly. This pattern helps with both water drainage and structural integrity, as the raised profile adds rigidity to the roofing system.

For flat sheets, the installation involves placing them directly onto the roof supports, with fixings at regular intervals, typically along the edges and the centre. For profiled sheets, fasteners are generally placed in the valleys of the profiles, ensuring they don’t interfere with the water drainage channels.

Fixing the Sheets

Roofing sheets are secured using screws, nails, or clips, depending on the material and profile. The fasteners should be positioned carefully to avoid damaging the sheets and should be sealed with rubber washers or gaskets to prevent water ingress. 

For metal roofing, it's essential to use corrosion-resistant fasteners to ensure longevity and prevent rusting. In polycarbonate and PVC roofing, it’s important to use the correct clips to prevent distortion from thermal expansion.

For profiled sheets, the fasteners typically go through the flat areas between the ridges or into the valleys, securing the sheets tightly to the roof battens or purlins. The correct tension is crucial, as over-tightening can lead to warping or cracking, while under-tightening could lead to leaks or loose sheets.

Sealing the Joints and Edges

Once the sheets are in place, all edges and overlaps must be properly sealed to ensure they are watertight. This is especially important where sheets meet at angles, ridges, or around roof penetrations. Sealant or butyl rubber tape is often used at the joints, and additional flashings may be installed around areas like chimneys, skylights, or vents. For profiled roofing, special closure strips are used at the roof’s edges to prevent wind-driven rain from entering between the corrugations.

Ridge and Hip Details

When installing the final rows near the ridge, a ridge cap or hip cap is used to seal the roof’s apex. This piece not only provides a clean, finished look but also prevents water from getting underneath the sheets at the highest point of the roof. It is important to ensure the ridge cap is sealed correctly to prevent leaks in this critical area.

Inspection and Finishing Touches

After installation, a thorough inspection should be carried out to ensure the roof is secure and weatherproof. This includes checking that all fasteners are tight, overlaps are correctly aligned, and the joints are properly sealed. If necessary, a final coat of protective finish, such as a painted coating or anti-corrosion treatment, may be applied, particularly for metal roofing, to increase durability and prevent rusting.