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Fitting Guide
Everything you need to know about installing roofing sheets, from purlin spacing to fixing methods. Follow our step-by-step guide for a professional finish.
1
Sheet Overlapping
Fixing our box profile sheeting is quick and easy. We advise you to overlap the drainage side of the sheet (as pictured). The groove drives any water away which is trying to get under the lap, ensuring a watertight seal.
2
Recommended Purlin Spacing
The spacing of your purlins depends on the thickness of the sheets used:
| Sheet Gauge | Max Purlin Spacing | Best For |
|---|---|---|
| 0.5mm | 1200mm | Standard domestic and light agricultural |
| 0.7mm | 1600mm+ | Industrial, commercial and heavy-duty |
Purlins should be a minimum of 50mm in width for easy and secure fixing of the sheeting.
Need purlins? We supply C Section Purlins and Z Purlins cut to your exact lengths.
3
Laying Roofing Sheets
Begin laying sheets from the eave and work towards the prevailing wind (primarily left to right). The side laps will then face away from the wind, preventing water from being forced into the lap.
Start at the eave (bottom edge)
Work towards the prevailing wind
Overlap side laps away from wind direction
Use minimum 150mm end lap overlap
4
Fixing Methods
Self-drilling tec screws are the most effective method for fixing down sheets. These can be used for timber purlins, steel purlins, and heavy sections.
| Location | Fixing Pattern |
|---|---|
| Standard/sheltered areas | Fix in every other trough |
| Exposed/windy areas | Fix in every trough |
| Side lap overlaps | Stitcher fixings every 500mm |
Shop fixings: We supply tec screws and stitcher fixings for both timber and steel purlins.
5
Mastic Butyl Sealant
Mastic butyl strip is the recommended sealant for profiled steel roofing and cladding projects. Used within the side and end laps of the roof sheet (not normally necessary on wall cladding), these sealants offer excellent performance when compressed.
Common bead sizes: 6 x 5mm or 3 x 9mm. Supplied on a roll with paper backing strip for easy application.
Order sealant: Browse our butyl sealant tape and foam infills for a weathertight finish.
6
Top Tips for a Professional Finish
Use foam infills at the ridge and eave to prevent birds and debris from entering
Always use colour-matched flashings for a clean, professional appearance
For agricultural buildings with livestock, consider anti-condensation sheets
Provide ventilation at the eaves and ridge to reduce condensation risk
Handle sheets with care to avoid scratching polyester paint finishes
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