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Fixing and securing sheets

We recommend the use of our self-drilling TEK screws with 5/16 hexagon heads and 19mm sealing washers, for fixing your roof.

The main fixings are used to transfer all the loads acting on the cladding back to the supporting structure and to form a watertight seal. These should be long enough to get a secure fixing into your purlins. Fixings consumption should be calculated as a minimum of five per m², exact fixing requirements will change depending the roofing scenario.

We supply fixings for timber*, light section and heavy section steel in varying lengths to suit your chosen profile.

*Recommended timber purlin size is 4" x 2". Timber Tek screws should not be used on anything smaller than a 2" x 2" timber support as the aggressive thread may split smaller timbers

Fixing recommendations

Box profile sheet fixings

Trapezoidal (or box) profiled sheets should be fixed through every valley/pan (lowest point of the profile) at every purlin, with extra fixings being used at the ridge and eaves profiles for added strength.

When fixing through the sheet directly into a timber purlin a 32mm timber TEK screw is recommended. When fixing through the sheet directly into a steel purlin a 25mm light section TEK screw or 35mm heavy section is recommended.*

3" traditional corrugated sheet fixings

Sinusoidal profiled sheets (otherwise known as wriggly tin) are normally fastened using longer screws through every second or third crown (highest point of the profile) to permit free drainage when used in roofing applications.

Corrugated metal profiles for walling applications may be valley fixed providing the sealing element is designed and shaped to ensure a seal against the curved valley profile.

When fixing through the sheet directly into a timber purlin a 65mm timber TEK screw is recommended. When fixing through the sheet directly into a steel purlin a 50mm light section or heavy section is recommended.*

Stitch screws

Stitch screws are smaller secondary fasteners and should be used for sheet side laps and the securing of flashings and ancillary components to the sheeting. Stitch screws are used for metal on metal fastening and do not require anchoring to a purlin. We recommend that stitch screws should be run every 300mm to 600mm along any metal joins.

*When fixing through additional materials before hitting a purlin (e.g. insulation or plywood boards the screw length may need to be extended. You will need to discuss your individual requirements with our technical team prior to placing an order)

Tek Screws washer compression

Washers under compression

Alternative fixing methods

Hook bolts

Used more frequently in the early years of metal profiles, hook bolts are not generally recommended today for metal roof sheeting largely due to the availability of self-drillers and tappers, as well as the safety risk to operatives associated with their method of installation. However, hook bolts are available if required.


Rivets are generally used for temporary or internal cladding and are not generally suitable for roofing.

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