Corrugated bitumen roof sheets are a popular choice for sheds, garages, workshops, and garden buildings thanks to their durability, weather resistance, and ease of installation. Whether you’re a DIY homeowner or a trade installer, fitting bitumen roofing correctly is essential to ensure a watertight, long-lasting roof.
This step-by-step guide explains how to install corrugated bitumen roof sheets properly, what tools you’ll need, and the most common mistakes to avoid.
What You’ll Need Before You Start
Before installation, make sure you have the correct materials and tools:
-
Ridge pieces (for pitched roofs)
-
Tape measure
-
Hammer or drill
-
Fine-toothed saw or utility knife
-
Ladder and safety equipment
Having everything ready before you begin helps ensure a smooth installation.
Step 1: Prepare the Roof Structure
Bitumen roof sheets must be installed onto a solid, level timber framework.
Key preparation points:
-
Use timber battens or decking boards spaced according to manufacturer guidelines
-
Ensure the structure is square and level
-
Check that the roof pitch meets minimum requirements (usually 5° or more)
-
Make sure the framework is securely fixed and free from sharp edges
A properly prepared structure is essential for roof longevity.
Step 2: Install Eaves Fillers
Eaves fillers are often overlooked but play an important role.
They:
-
Close the gaps created by corrugations
-
Prevent wind-driven rain entering the roof
-
Stop insects, birds, and debris from getting inside
Install eaves fillers along the lower edge of the roof before laying the sheets.
Bitumen eaves fillers
Step 3: Position the First Sheet Correctly
Start installation from the bottom edge of the roof, working upwards.
Position the first sheet so that:
-
It overhangs the eaves slightly (usually 50–75mm)
-
The corrugations run vertically from ridge to eaves
-
The sheet is square to the roof edge
Taking time to align the first sheet correctly makes the rest of the installation much easier.
Step 4: Fix the Sheet in Place
Use bitumen-specific fixings or nails to secure the sheet.
Fixing tips:
-
Fix through the crest of the corrugation, not the valley
-
Space fixings evenly along battens
-
Do not overtighten — allow for natural movement
-
Use washers where supplied to improve weather resistance
Step 5: Overlap Sheets Correctly
Correct overlaps are essential to prevent leaks.
-
Side overlap: at least one full corrugation
-
End overlap: typically 150–200mm, depending on roof pitch
Ensure overlaps face away from prevailing wind where possible.
Step 6: Continue Across the Roof
Repeat the process across the roof:
-
Lay each sheet with correct overlaps
-
Keep sheets aligned and straight
-
Fix securely but without stress
Regularly check alignment as you go to maintain a neat finish.
Step 7: Fit Ridge Pieces (Pitched Roofs)
If your roof has a ridge, ridge pieces are essential.
Ridge pieces:
-
Seal the apex of the roof
-
Improve wind resistance
-
Provide a clean, finished appearance
Fix ridge pieces through the crest of the corrugations into the timber beneath.
Corrugated bitumen ridge caps
Step 8: Final Checks
Once installation is complete:
-
Check all fixings are secure
-
Ensure overlaps are consistent
-
Inspect for gaps or loose edges
-
Clear any debris from the roof
Your corrugated bitumen roof should now be fully weatherproof and ready for use.
Common Installation Mistakes to Avoid
-
Fixing through the valleys instead of crests
-
Overtightening fixings
-
Incorrect overlap distances
-
Skipping eaves fillers
-
Installing sheets on an insufficient roof pitch
Avoiding these mistakes will significantly extend the life of your roof.
Frequently Asked Questions
Can I install corrugated bitumen roof sheets myself?
Yes. Bitumen roofing is designed for straightforward DIY installation using basic tools.
Do I need felt under bitumen roof sheets?
No. Corrugated bitumen sheets are installed directly onto timber battens or decking.
How much overlap do bitumen roof sheets need?
Typically one corrugation at the side and 150–200mm at the ends.
Should I pre-drill holes in bitumen sheets?
No. Bitumen sheets can be fixed directly using appropriate nails or screws.
Can bitumen roof sheets be cut to size?
Yes. Use a fine-toothed saw or sharp utility knife.
