If you're looking to install bitumen roof sheets on your shed, garage, or any other extension, you will need to ensure that you’re prepared for the installation process. This article will guide you through the process of fitting bitumen roof sheets, from things you need and installation procedures to tips for ensuring a successful installation. Whether you are looking to upgrade, replace, or install a new roof, you will find all the information below.
Advantages of installing bitumen roof sheets
Bitumen roof sheets are an excellent roofing material to consider if you’re looking for an affordable and long-lasting roof system. Below are some of the main benefits of using bitumen sheets:
- They are lightweight, easy to cut to size, and install.
- They are waterproof and have excellent acoustic and heat insulation properties.
- They are seamless and highly resistant to forming gaps and cracks on their surface.
- They are very cost-effective and one of the most affordable roofing materials available on the market. Prices for high- quality bitumen sheets can range between £10 to £25.
- Bitumen sheets are known for their durability and high tensile strength. Therefore, a properly installed bitumen roof can protect your property from all weather conditions and can easily last up to 10 years.
Things you will need:
- Purlins on the rafters
- Bitumen roofing sheets
- Bitumen ridge sheets
- Measuring tape
- Chalk or pencil
- A retractable knife or coarse-bladed saw
- Corrugated bitumen fixings or screws with safe-top caps and washers
- A ladder for roof access.
Things to consider:
- It's always best to hire a professional rather than put your health and safety at risk, especially if you don’t feel comfortable installing roofing sheets.
- A sturdy ladder and even a rope harness may be required for the installation. We also recommend reading our guide on how to work safely on a roof because it can be risky when working at heights.
- Corrugated bitumen sheets will need to be placed correctly up during installation. This is because the top of the sheet has a smooth grain surface, while the opposite side has a coarse or rough surface.
How to fit bitumen roof sheets
Before you begin, measure the roof dimensions (length and breadth) and choose the correct size and the number of bitumen roof sheets for the project. Once this is done, follow these simple steps:
- Measure the roof’s pitch to determine the correct placement of purlins on the rafters. A roof pitch of 10–15 degrees will have purlins evenly placed at 45 cm apart, whereas a pitch of more than 15 degrees will have purlins spaced 61 cm apart. For anything below 10 degrees, you must fit bitumen sheets to a fully supported roof deck.
- Mark the bitumen sheets with chalk or pencil and cut them to size using a coarse-bladed saw. You can also use a trimming knife to cut the roofing sheets. If you require further guidance on how to cut plastic corrugated sheets, click here.
- Place the first sheet on the roof deck, leaving at least 5 cm of overhang for water drainage. Position the sheet carefully, ensuring it aligns with the eaves and the roof edge.
- Nail the bitumen sheet to the roof deck starting at the edges—fix nails on the corrugated part of the sheet. You can also use screws with safe-top caps and washers instead.
- Overlap one corrugation of the second sheet onto the first sheet and secure it with nails or screws. Repeat the process until you reach the edge of the roof.
- On large roofs, the second-stage bitumen sheets will overlap the first stage by at least 20 cm. Repeat the process in a broken bond pattern while securing the sheets with nails or screws at each overlap. The sheet edges on the sides can be overhung by at least 5 mm or folded and nailed to the purlins.
- Once the sheets are secured, you can fix bitumen ridge pieces to the roof. Mark the fixing line to ensure correct alignment, then carefully bend the ridge sheets to sit on the roof slopes.
- Overlay the ridge pieces to the roof and secure them using nails or screws, working from one side to the other.
- Check if all sheets are correctly aligned and fixed to the roof by carefully inspecting and nailing the corrugation as needed.
- Congrats! You have successfully fitted bitumen sheets on your roof.
Can you walk on bitumen roof sheets?
Although bitumen roof sheets have a high tensile strength, walking on bitumen sheets is generally not recommended as this can be dangerous, especially if they have not been secured properly. Instead of walking on bitumen sheets, you should use wooden planks supported by roof purlins or ladders.
