21/10/2025
How to fit roofing sheets, a quick, no‑nonsense guide
Getting a watertight, tidy finish comes down to prep, laying direction, and consistent fixings. Here’s a clear, site-ready rundown you can share with the team.
Before you start
• Measure twice and set your datum line square to the eaves
• Check purlins are level, aligned, and at the correct centres
• Lay out tools: tape, square, snips/nibbler, drill/driver, chalk line, sealant, PPE
• Safety first: edge protection, fall restraint, gloves, eye and hearing protection
Laying direction
• Start at the eaves on the end of the roof that’s opposite the prevailing wind
• Ensure the side‑lap faces away from the wind to reduce driven rain
Step‑by‑step
1. Eaves prep
◦ Fit eaves fillers/closures where specified
◦ Offer up gutter and check overhangs
2. First sheet = your reference
◦ Position the first sheet square to the eaves and verge
◦ Tack a couple of fixings, check alignment, then fully fix
3. Fixing pattern
◦ Use appropriate TEK/self‑drilling screws with sealing washers for the substrate (timber or steel)
◦ Fix in the crown or trough as your profile requires; keep rows straight using a chalk line
◦ Stitch side‑laps with smaller stitcher screws at regular centres
4. Side‑laps
◦ Apply butyl mastic tape along the lap line for roofs (often not required for walls)
◦ Engage the lap fully; add stitchers to prevent lift or rattles
5. End‑laps (if needed)
◦ Overlap sheets in the flow of water
◦ Use continuous butyl tape and place primary fixings either side of the lap
6. Work across the roof
◦ Add the next sheet, check it’s seated tight on the side‑lap, then repeat the fixing pattern
◦ Re‑check squareness every few sheets to avoid creeping out at the verge
7. Flashings and finishing
◦ Fit ridge/hip/verge flashings with sealed laps and stitcher screws
◦ Install foam fillers where profiles meet flashings for a clean, weather‑tight finish
◦ Remove swarf and debris to prevent rust spots
Cutting tips
• Cut off the roof where possible using nibblers or shears (avoid hot cutting that burns coatings)
• Touch up cut edges only if the system specifies; otherwise leave factory finish intact
Common mistakes to avoid
• Wavy fixing lines and overtightened screws crushing washers
• Side‑laps facing into the wind
• Missing sealant at end‑laps on roofs
• Leaving swarf on the sheet surface
Need a deeper dive?
See our fitting guide with diagrams
🔗 https://mightystructural.com/shop/fitting-guide/
Questions on sheet type, fixings or spacing?
📞 01922 649795 | 📧 [email protected]
🌍 Order online anytime ➡ www.mightystructural.com
