Purlin Installation Guide
Whichever Cladco roofing sheet you choose, making sure it’s installed on a strong, well-supported framework is a vital part of any roofing project. Using reliable, high‑quality purlins in your roof structure helps distribute the weight of your metal roofing sheets evenly, improving overall structural integrity.
In this guide, we’ll provide you with practical advice on how to support roof purlins correctly, allowing you to create a safe, durable roof construction built to last.
CHOOSING THE RIGHT PURLINS
Z Purlins
Available in multiple lengths up to 9m, our punched and unpunched structural‑grade Z purlins create a strong, stable roofing framework. Manufactured from 1.8mm thick Z39 galvanised steel, they provide reliable support for low‑sloping and flat roofs, with compatible purlin cleats and sleeves helping to ensure a secure, professional installation.
Thanks to their Z‑shaped profile, these purlins can be lapped over supports to form a continuous beam, which helps to improve strength across longer spans. This design performs efficiently under load and reduces twisting, making Z purlins a popular choice for roofing projects where durability, stability, and long‑term performance are essential.
C Purlins
Ideal for supporting wall cladding sheets across a range of building projects, our C purlins range from 1.5m to 9m long and help create a sturdy, dependable framework for your structure. Manufactured from high‑quality Z39 galvanised steel and available punched or unpunched, they provide a long‑lasting, corrosion‑resistant frame built for reliable performance.
C purlins are most commonly used for wall cladding applications and structural projects such as mezzanine floors and platforms. Their simple, open‑section design makes them easy to fix to steelwork and ideal for side‑fixing installation, providing a practical, versatile solution where roofing‑specific performance is not required.
*When installing cleats, position them within ±5mm of their intended location and align them within 1°. Allowing this tolerance may result in a total spacing variation of up to 10mm between adjacent purlins or rails.
Purlin Spacing
To ensure your metal sheets can be easily fastened to the purlins, a top flange width of at least 50mm is required to provide sufficient fixing space. Once in position, the roof purlins should be spaced no further than 1.2m apart when installing 0.7mm thick metal roof sheets, and 1m apart when installing 0.5mm thick sheets. While exact requirements will vary from project to project, this provides a useful rule of thumb. If in doubt, always consult a qualified professional before installation.
How To Support Roof Purlins
Roof purlins must always be securely fixed to the rafters, with all joints and overlaps fully supported. Where purlins meet or extend over longer spans, purlin sleeve connectors can be used to join sections together, while purlin cleats help provide a strong, stable fixing point. Once installed, it’s important to inspect the framework to ensure the purlins are correctly aligned, level, and evenly spaced. Incorrect spacing or insufficient support can place unnecessary strain on the structure and may lead to damage once the metal sheets are fitted.
*Please note that any spacing and installation guidance is general guidance only, and final requirements will depend on loading, building type and location.
PURLIN ACCESSORIES
Z & C Purlin Cleat Bracket
An effective solution for fixing purlins to supporting fixtures, including RSJs (rolled steel joists), this pre‑punched cleat bracket helps create a strong, reliable connection. Suitable for installation on top of or inside the joist, it’s compatible with both C and Z purlins and manufactured from corrosion‑resistant galvanised steel.
Installation Guidance (for Z Purlin)
When installing your Z purlins, the metal cleat bracket should be securely fixed to the rafter or primary steelwork first, using compatible bolts. The vertical face of the Z purlin is then bolted to the cleat bracket using the pre‑punched holes. This method provides strong vertical support and helps maintain correct purlin alignment.
Installation Guidance (for C Purlin)
If you’re installing a C purlin, the cleat bracket should be securely fixed to the supporting rafter or steelwork using suitable bolts, such as our 60mm bolt set for purlins. The C purlin is then seated onto the cleat and bolted vertically through the pre-punched holes in the base of the section. This provides a stable fixing point and helps keep the framework level and secure.
C Purlin Cleat Bracket (Side Installation)
Engineered from S450 galvanised steel, this boltable cleat bracket is designed for projects that require C purlins to be fixed into the side of structural steel work, such as the construction of mezzanine floors and platforms. Their fully bolted design removes the need for on-site welding, making installation quick and efficient.
*We recommend checking the product details on our website to make sure this cleat bracket is suitable for your specific project before purchasing.
Installation Guidance
When installing a C purlin cleat bracket, the cleat should first be bolted securely to the supporting steelwork. The C purlin is then positioned inside the cleat and fixed through the bracket face using suitable purlin bolts. This method creates a stable side‑fixing suitable for structural applications such as mezzanine floors.
Z Purlin Sleeve Connector
Designed to create a neat, continuous line of support across roofing and cladding frameworks, this purlin sleeve connector reinforces joints between Z purlins to form a stable fixing base. Each connector is custom‑manufactured specifically for our Z purlins, ensuring a precise fit and consistent support at every connection point.
Purlin sleeve connectors are used where Z purlins meet over longer spans, allowing sections to overlap and act as a continuous beam. This improves structural continuity and helps transfer loads evenly through the framework, reducing stress at joints and supporting long‑term performance.
Installation Guidance
Position the sleeve connector at the joint between two Z purlins, ensuring it fits securely over both sections before fixing. Once aligned, bolt through the purlins to secure the connection. Use one sleeve per purlin joint to maintain consistent support across the framework. Always wear protective gloves during handling and installation.
Purlin Bolt Set (M16 x 60mm)
A simple and reliable solution for securing purlins, this M16 x 60mm purlin bolt set helps create a rigid, stable framework for roofing or cladding projects. Comprising a bolt, nut, and washer, it’s designed to fix purlins, cleats, and sleeves into both C and Z purlins with minimal hassle.
