Sealing upstands and abutments with flashing tape
Where a flat roof meets a wall, parapet or rooflight upstand is where many leaks start. Movement, weather and old lead or mastic all take their toll. Self-adhesive flashing tape gives a fast, cold-applied way to seal these details, and it's widely used as a lead flashing alternative.
Choose the right width
You need enough tape to turn up the vertical face and lap well onto the roof. 200mm covers most upstands and abutments. 300mm gives a deeper turn-up and a wider lap for parapets and taller details. See the width guide.
Step 1: Prepare both faces
Clean the vertical face and the roof surface along the full length of the detail. Remove loose mortar, dust, old mastic and moss. On brick or render, the surface must be sound and dry. Let everything dry fully.
Step 2: Mark your line
Decide how far up the wall the tape will go and mark a level line. A straight top edge looks professional and sheds water cleanly.
Step 3: Fold and fit
Crease the tape lengthways where it will turn from wall to roof. Fit it into the internal corner first, then press it up the wall to your line and out onto the roof, working out air as you go.
Step 4: Corners
- Internal corners: run the first length past the corner, then lap the next length over it, pressing well into the angle.
- External corners: cut and fold the tape around the corner and add a second patch over the top. External corners take the most stress.
Step 5: Roll everything
Roll the whole detail firmly with a seam roller, focusing on the top edge, the crease and any laps. The bond starts working straight away and strengthens over time.
Finishing
Supraseal® is UV stable, so it can be left exposed, and it can be painted to blend with the wall. It's backed by a 10-year warranty.