Best Fixing Patterns & Nail Layouts for Bitumen Roofing (Complete Guide)

February 1, 2026

The Correct Way to Nail or Screw Corrugated Bitumen Sheets for a Strong, Leak-Free Roof

When installing corrugated bitumen roofing sheets, the fixing pattern is just as important as the sheets themselves. Poor fixing layout is the number one cause of:

Lifting sheets in high winds
Leaks around nails
Cracked or distorted sheets
Noisy roofs that “rattle”
Premature roof failure

This guide explains the best fixing patterns, nail positions, spacing, and quantities for a long-lasting, watertight bitumen roof. Whether you're roofing a shed, pergola, lean-to, garage, or garden building, this guide ensures you get it right first time.

1. Why Fixing Pattern Matters

Bitumen sheets are lightweight and flexible — which is a huge advantage — but it means they must be fixed correctly to prevent movement.

A proper fixing pattern ensures:

✔ Maximum wind resistance
✔ Proper sheet tension
✔ No leaks through fixings
✔ Clean appearance
✔ Long lifespan

Skipping or incorrectly spacing fixings is the most common DIY mistake.

2. Fixings You Should (and Shouldn't) Use

✔ Use Official Bitumen Sheet Fixings:

Colour-matched caps
Rubber sealing washers
Ring shank nails or screws
UV-stable components

These guarantee a waterproof seal.

❌ Avoid:

Standard roofing nails
Screws without washers
Staples
Fixings through valleys

Improper fixings will leak and cause failures.

3. The Golden Fixing Rules (Apply to Every Roof)

✔ Fix on the crest of the corrugation

Never in the valley — water collects there.

✔ Use a fixing at every corrugation along the eaves and ridge

This is critical to preventing wind uplift.

✔ Fix every 2 corrugations at intermediate battens

Stronger structures can optionally fix every 3 on sheltered roofs.

✔ Fix the side lap every 2 corrugations

Keeps the overlap tight and watertight.

✔ Do not overtighten fixings

The washer should sit firm, not crushed.

4. Fixing Pattern Diagram (Explained Step-by-Step)

Below is the industry-standard fixing layout for corrugated bitumen sheets:

⭐ A – Eaves (Bottom Edge): Fix Every Corrugation

Example: 9 corrugations = 9 fixings
This is the most important fixing line of the entire roof
Prevents sheets lifting or “fluttering” in high winds

⭐ B – Ridge (Top Edge): Fix Every Corrugation

Mirrors the eaves fixing pattern
Ridge pieces overlap the sheets by 125mm+
Stops uplift at the top of the roof

⭐ C – Intermediate Battens / Purlins: Fix Every 2 Corrugations

This includes:

Battens on sheds
Purlins on pergolas
Rafters with cross-battens

Fixings should be:

Straight
Evenly spaced
At the highest point of the corrugation

⭐ D – Side Lap: Fix Every 2 Corrugations

Anywhere two sheets overlap:

Fix on the upper sheet
Through the crest
Every second corrugation

This stops sheets separating or flapping along the join.

5. How Many Fixings Per Sheet Should You Use?

The quantity depends on the roof style:

Sheds / Small Garden Buildings

✔ 18–22 fixings per sheet

Medium Roofs (Garages / Lean-Tos)

✔ 22–26 fixings per sheet

Exposed or High-Wind Areas

✔ 26–30 fixings per sheet

More fixings = stronger roof.
Fixings are cheap — don’t cut corners.

6. Fixing Patterns for Different Roof Types

A) Sheds

450mm batten spacing
Eaves: fix every corrugation
Middle: every 2 corrugations
Overlap: 1 corrugation (10°+ pitch)

B) Pergolas & Open Structures

600mm purlin spacing
Always fix side laps with extra care
Use screws instead of nails for wind exposure

C) Lean-To Roofs

Priority on the side most exposed to wind
Fix every corrugation along high edges
Check pitch (minimum 5°)

D) OSB / Plywood Decking

Fixings every 300mm
Fix on crests only
Sheets sit perfectly flat

7. Correct Fixing Technique (Important)

✔ Step 1 — Pre-drill holes (optional but recommended)

Especially in cold weather
Prevents sheet cracking
Hole should be 1–2mm larger than shank

✔ Step 2 — Insert fixing vertically

Not angled — angled fixings will leak.

✔ Step 3 — Tighten until washer compresses

But do NOT crush the corrugation.

✔ Step 4 — Close the cap

This protects the fixing from UV and water.

8. Fixing the Ridge with Correct Pattern

Ridges need special attention.

✔ Fix every corrugation

✔ Overlap ridge pieces by 150mm

✔ Fix both sides of ridge (left & right)

✔ Apply fixings at both sheet joins

This ensures a strong, waterproof ridge line.

9. Fixing the Verge (Side Edges)

The verge is exposed to wind pressure.

✔ Use verge trims or barge boards

✔ Fix through every corrugation

✔ Ensure no overhang without support

A loose verge is the first place roofs fail.

10. Most Common Fixing Mistakes (Avoid These)

❌ Fixing through valleys → leaks
❌ Too few fixings → roof flaps in wind
❌ Overtightening → crushed sheets
❌ Incorrect overlap direction
❌ Not fixing enough at eaves or ridge
❌ Using wrong fixings
❌ Fixing into weak/rotten timber

Follow this guide and you’ll avoid all of them.