You’ll hear the term ‘roof fixing’ from time to time if you own or are involved in the maintenance of commercial buildings. Roof fixings, panel or cladding fixings consist mostly of self drilling screws. These types of screws fix steel roof sheets and wall cladding panels to roof battens. The battens are attached to rafters and the rafters are held in position by the purlins. So a roof fixing is the last thing holding the outer envelope or skin of a building in position. Needless to say they do a important job.
What are roof fixings and roofing screws?
A roofing screw is fundamentally a roof fixing. They are one in the same. Just one component in the wider assembly of a roof system. Roofing screws, panel fixings and cladding screws are all the same and essentially do the same job. They hold cladding panels and roof sheets onto the framework of a building. Historically mushroom head bolts and nuts where used to fix panels in position. However installation of these was labour-intensive and costly. Roof and panel bolts also suffered from corrosion and in some cases even worked loose. Self-drilling screws are quicker and easier to install, perform better and suffer less from corrosion.
What are self-drilling and Tek screws?
A self drilling screw or bolt has a drill bit at its end point. The middle is threaded to grip the material it is drilled into. They usually have a hexagonal screw head. Self drilling screws are also known as tek or self-tapping screws.
Theses screws are normally installed with high-speed impact electrical drills. This helps them to initially penetrate the metal, wooden, concrete, masonry or PVC substrate. The threaded centre length then grips the substrate and hold panels and other components in place. When used externally self-drilling, tek and self tapping screws usually feature bonded rubber washers below the screw head. This creates a weather proof seal around the hole.
Different screws for different roofs, walls and panels
The type of fixing you need depends primarily on the the material you’ll be fixing to. And its not just roofs. Self drilling screws are also used for wall cladding and panelling. Steel battens are most common in the UK and EU, followed by timber and in some instances concrete and masonry. When fixing to steel you need compatible screws. Likewise timber battens require timber compatible screws and so on.
Modern stainless steel fixings with added protection from nylon moulded heads have exceptional resistance to weathering and corrosion. For roof and panel fixings without moulded heads, hex caps are available and can be fitted afterwards. This provides added protection for the bolt head against the elements. Screw fixings, like any other metal components, do suffer from corrosion eventually. This can be treated by encapsulating the fixing with a special coating to prolong its lifespan.
Light section fixing screws
Heavy section fixing screws
Heavy section fixing screws are used for fixing metal to heavy section steel. They are single action installation and widely used for cladding and roofing applications to hot rolled purlins and feature a fine self-tapping metric thread. They are durable and able to withstand over 1000 hours of salt spray testing. If left untreated after their expected working lifespan they do eventually suffer from corrosion.
Used for stitching sheet metal without the need to pre-drill a hole. Self-drilling point and tapered shank, with a hexagon head and bonded washer seals. Exterior plating gives a reliable and durable corrosion resistant coating which can resist over 1,000 hours of salt-spray.
Composite panel fixing screws
Composite panel fixing screws are predominately used to fix composite panel sheets to cold rolled rails and purlins. The hi-threads support the top of the sheet offering greater stability. No pre-drilling is required with this type of screw fixing.
Gash point self-drilling screws
Typically used for fixing thin gauge steel to timber. Gash point self-drilling screws usually have a bonded washer. The point on this type of screw gives easy initial penetration of the metal before it drills and taps into the timber substrate. The sharp threads allow for low torque and strong fixing.
Bi-metal wing-drill screw fixings
Masonry screw anchors, aka anchor bolts are typically used to fasten fittings directly to masonry, concrete and stone. They have carbon steel, hex heads and are often zinc-plated. The long tough thread taps into and grips the substrate. Masonry fixings come in a range sizes and are suitable for multiple applications. They come in fully and partially threaded configurations.
Screw covers and caps
Screw fixings maintenance
There isn’t much you can do on a regular basis to maintain a self-drilling screw once its been installed. Keeping it clean, free from debris and away from standing water would be the best advice. Making sure your screw heads are capped will prolong their usefulness. However if they are exposed to the elements consider treating them with corrosion protection paint. This process is called fixing encapsulation, information about this can be found here.
There is more to the humble panel fixing than some might think. They perform an important task, come in all shapes, sizes and configurations and suffer from corrosion, just like any other roof component. They might be small but they do a big job.