How to Fit Metal Roof Flashings on Box Profile Roofs

Fitting flashings properly is what separates a roof that stays dry from one that drips after the first wet week. This guide is aimed at roofers and builders working with plastisol-coated box profile sheets across the North East, Yorkshire and the North West. It follows the same sequence we talk through when customers collect from our Newcastle workshop or order online for site delivery.

Tools and materials

Have these ready before you go up:

• Aviation tin snips for trimming
• Cordless driver with a magnetic hex socket, or our TEK screw socket driver
• TEK screws with EPDM washers, plus colour caps if the finish matters
• Butyl lap tape for sealed overlaps
• 32/1000 foam fillers for ridge and eaves on that profile
• Gloves and proper work-at-height kit

1. Check the sheets first

Flashings will not hide a bad sheet layout. Confirm end laps and side laps are correct, purlin fixings are in, and sheets are sitting flat. On older farm buildings in County Durham or North Yorkshire, check for sagging purlins before you dress new flashings over them.

2. Dry-fit every flashing

Offer up the length, mark cuts, and check that laps run with the fall. Our standard 130° ridge, 90° corner barge and 90° upstand pieces are 3m, so plan joints before you drill.

3. Foam fillers at ridge and eaves

On 32/1000 box profile, push the matching foam fillers into the profile before the ridge or eaves flashing goes on. That closes the corrugation gaps against wind-driven rain. Skip this on an exposed Pennine or coastal site and you will hear about it later.

4. Fix ridge flashings

Centre the ridge over the apex so both wings sit evenly. Fix through the high points of the sheet into the structure, not into empty troughs. Lap adjoining ridge lengths by at least 150mm in sheltered spots and more in exposed locations. Run butyl tape in the lap if you want a belt-and-braces seal.

5. Barge and abutment details

For verges, the barge should cover the sheet edge cleanly and throw water off the wall. For abutments, the upstand needs a proper chase or cover flashing into the wall. Do not rely on a smear of silicone alone against brickwork that moves with frost.

6. Drip trays on long slopes

Where sheets butt on a long run, fit a drip tray under the joint before you close everything up. It is cheap insurance on industrial units around Teesside, Leeds and Manchester.

Common mistakes we still see

• Fixing through the low part of the profile so water pools at the screw
• No foam fillers on box profile ridges
• Laps facing up the slope
• Mixing colours between sheets and flashings
• Leaving cut edges without touching up on visible elevations

Need the parts in one delivery

We supply flashings and accessories together from Newcastle upon Tyne for sites across Northern England. Browse flashings and accessories, or call 01912 853848 if you want a quick check on angles or colours before you climb the roof.