How to Seal Verges & Ridges on Bitumen Roofing (Stop Wind Uplift & Leaks)

February 3, 2026

The Complete Guide to Finishing Corrugated Bitumen Roofs Properly

Sealing the verges (side edges) and ridge (top edge) of a corrugated bitumen roof is essential for keeping your roof watertight, wind-resistant and long-lasting.
Most leaks and uplift problems don’t come from the sheets — they come from poor ridge or verge installation.

Whether you're roofing a shed, garage, pergola, lean-to or garden building, this guide explains exactly how to seal the ridge and verges correctly, what fixings to use, and mistakes to avoid.

1. Why Proper Ridge & Verge Sealing Matters

✔ Stops wind uplift

Unsealed edges act like a wind sail and can lift sheets in storms.

✔ Prevents rainfall blowing under sheets

Especially important on exposed sites.

✔ Keeps out debris, insects and birds

Prevents nesting between sheets and timber.

✔ Improves waterproofing

Most leaks occur at sheet joins, not in the middle.

✔ Creates a clean, professional finish

Neat edges = a long-lasting, better-looking roof.

2. What You Need for Sealing Ridges & Verges

✔ Matching Bitumen Ridge Pieces

Available in:

Black
Green
Red
Brown

✔ Bitumen Verge Trims / Barge Boards

Used to secure the outer sheet edge.

✔ Fixings (with caps & rubber washers)

Essential for a watertight seal.

✔ Tools

Hammer or drill/driver
Tape measure
Marker or chalk
Gloves
Ladder

3. How to Seal the Ridge (Top of Roof)

The ridge is the highest point of the roof and the area most exposed to wind and driving rain.

Step 1 — Overlap the Sheets Correctly

Your bitumen sheets should:

Meet evenly along the ridge
Overlap the ridge by at least 125–150mm
Have fixings on the top corrugation line

If sheets are uneven, trim before adding your ridge.

Step 2 — Lay the Ridge Centre Line

Place the ridge so that:

The centre sits exactly over the ridge line
One side of the ridge overlaps each slope evenly
It follows the angle of the roof naturally

Most bitumen ridge pieces are flexible to match your roof pitch.

Step 3 — Fix the Ridge at Every Corrugation

This is essential to prevent wind uplift.

✔ Fix through every crest of the corrugation
✔ Fix both sides of the ridge
✔ Use fixings with rubber sealing washers
✔ Ensure caps are closed to protect the fixing head

For maximum strength, start by fixing at the:

Centre
Two ends
Then work along the ridge line evenly

Step 4 — Overlap Ridge Pieces

If you need multiple ridge pieces:

Overlap by 150–200mm
Fix through both layers
Ensure the overlap faces away from the prevailing wind

This prevents driving rain from flowing under the lap.

4. How to Seal the Verges (Side Edges)

Verge sealing prevents wind-driven rain and stops the outer sheet lifting or curling.

Option 1 — Using Bitumen Verge Pieces (Recommended)

Step 1 — Position the Verge Trim

Place the verge so it covers the sheet edge
Ensure it sits on top of the corrugation
Keep it straight along the roofline

Step 2 — Fix Through Every Corrugation

Just like the eaves, verge edges take the brunt of wind uplift.

✔ Fix every corrugation
✔ Use sealed fixings
✔ Do not overtighten
✔ Ensure the trim is flush with the sheet

Step 3 — Overlap Multiple Ver g e Pieces

If your roof is long:

Overlap verge trims by 150mm
Fix through both layers
Ensure smooth alignment

Option 2 — Using Timber Barge Boards (Traditional Method)

If you prefer timber finishing:

Fix timber barge board along the roofside
Sheets rest against it securely
Fix through every corrugation into the timber
Paint or weatherproof timber for longevity

This creates a classic shed-style finish.

5. Tips for a Windproof, Long-Lasting Finish

✔ Fix every corrugation on both the ridge and verge

This prevents gaps and uplift.

✔ Check sheet alignment before fixing the ridge

A crooked line will cause sealing gaps.

✔ Always fix on the crest, never the valley

The valley is where rain flows.

✔ Use more fixings on exposed roofs

High-wind areas need tighter fixing patterns.

✔ Keep overlaps facing away from the wind

This prevents capillary leaks.

6. Common Ridge & Verge Mistakes to Avoid

❌ Fixing in the valleys
❌ Using too few fixings
❌ Leaving the verge edge floating
❌ Incorrect ridge overlap direction
❌ Overtightening fixings (crushes bitumen)
❌ Not sealing the top corrugation line
❌ Letting ridge pieces overlap too little (<100mm)
❌ Not using sealing washers

Avoid these and your roof will perform flawlessly.