Roofing and cladding screws can look very similar. Two fixings may share the same length and head style but have different drill points, threads and washers because they are designed for different connections.
Joining overlapping sheets, securing a composite panel to steel and fixing a sheet to timber each place different demands on the fixing. Understanding those differences makes it easier to narrow down the options and order the right product for the job.
Start with the Connection
The first distinction is between a stitching screw and a primary fixing.
Stitching screws, often called stitchers, join overlapping profiled sheets or secure flashings and trims. Their role is to connect those components together.
Primary fixings secure the sheet or panel to the supporting structure, such as a steel purlin or timber rail.
A profiled-sheet roof may use both: primary fixings to secure the sheets to the purlins, with stitchers at the sheet laps where specified. Each performs a different job and needs to be selected for the connection it is intended to make.
Match the Fixing to the Supporting Material
The supporting material determines the type of point and thread required.
For steel supports, the thickness of the steel is a key starting point. Light steel and heavy steel fixings use drill points and thread forms suited to their stated applications. A longer screw still needs the correct drilling capability and thread engagement for the steel beneath it.
For timber supports, the fixing uses a point and thread designed to enter and engage with the timber. The required embedment into the supporting purlin or rail is an important part of choosing the length.
Descriptions such as light steel, heavy steel and timber help identify the product family. The individual fixing specification provides the detail needed for the particular connection.
Understand the Difference Between Sheet and Panel Fixings
Single skin sheets and composite panels have different build-ups, which affects how they are fixed.
A single skin fixing passes through the profiled sheet and engages with the supporting steel or timber. A composite panel fixing passes through the panel’s outer facing, insulation core and inner facing before reaching the support.
The composite panel fixings in Leoclad’s Specialist Imported Range use a lower thread suited to the supporting material, together with an upper support thread beneath the head. This upper thread engages the panel’s outer sheet and helps support it beneath the head and sealing washer.
The panel thickness therefore matters alongside the supporting material and the fixing’s thread arrangement. Length is only one part of that specification.
Know What Drilling Capacity and Clamping Range Mean
These two terms describe different aspects of a fixing.
Drilling capacity relates to the metal thicknesses and arrangement the fixing is designed to drill within its stated application.
Clamping range describes the permitted build-up the fixing can accommodate, measured according to the manufacturer’s definition. It is not automatically the same as the nominal panel thickness or overall screw length.
Check the product data sheet for the fixing’s stated drilling capacity and panel or clamping range. Our Resource Centre brings together product data sheets and selection guidance to help you check those details before ordering.
For timber applications, the length also needs to provide the required engagement into the support after passing through the sheet or panel.
Together, these details explain why ordering by length alone can lead to the wrong fixing, even when it appears long enough for the job.
Consider the Washer, Material and Coating
The washer and finish are part of the fixing specification too.
A bonded sealing washer helps distribute load around the fixing point and form a seal when correctly installed. The washer size and sealing material need to suit the sheet or panel and the intended connection.
Coated carbon steel, stainless steel and bi-metal fixings provide different material options. Bi-metal roofing fixings combine a stainless steel body with a hardened steel drilling point.
The appropriate choice depends on the building’s use, environmental exposure, adjoining materials and project requirements. A colour match can provide a consistent appearance, but the underlying material and coating specification determine the corrosion protection being offered.
Our Roofing Fixing Coatings Explained article looks at the different finishes available and explains what salt spray test figures can tell you.
Where a project specification or fixing schedule is available, it provides the starting point for selection alongside the relevant product data and installation guidance.
Find the Right Fixing with Leoclad
Leoclad Supplies supports contractors, distributors and merchants with roofing and cladding products, clear information and practical product knowledge.
Our Specialist Imported Range includes stitching screws and separate fixing families for single skin sheets and composite panels, with options for light steel, heavy steel and timber.
To help us narrow down the appropriate options, tell us what is being fixed, the supporting material and its thickness, and the sheet or panel build-up. Include any specified fixing requirements or existing product reference, together with the quantity required and delivery postcode.
Photographs, drawings and specification extracts can also help explain the connection.
We can discuss the application, identify relevant product options and provide the available technical information before you order.
Contact the Leoclad team to discuss your fixing requirements.