Faq
- Can I install I install Onduline sheets upside down?
- Which way up is an Onduline sheet fixed?
- Can I install Onduline roof sheets flat?
- How long is BARDOLINE guaranteed for?
- Where can I find Onduline installation instructions?
- What is the minimum pitch for Onduvilla tiles?
- How many nails should I use per Onduvilla tile?
- What is the overhang required for ONDUVILLA tiles?
- Fixing an Eaves Ventilation Strip
- What is the weight of an Onduline sheet?
- Can you fix Onduline to a curved Roof?
- Are Onduline sheets resistant to mould and mildew?
- How can I cut an Onduline sheet?
- Can Onduline sheets replace corrugated metal roofing?
- How do I replace a shed roof with Onduline sheets?
- Can I install Onduline sheets on top of the existing shed felt?
- Can I install Onduline roofing sheets directly onto timber boards?
- What should my roof pitch be to install Onduline?
- Can condensation form beneath an Onduline roof?
- How many fixings do I need per Onduline sheet?
- Is watertighness and waterproofing also warrantied for low pitched roofs?
- Do Onduline roofing sheets need ventilation?
- Can I install ONDULINE CLASSIC as a fence?
- Do I need a breathable membrane under Onduline roofing?
- How do you cut an Onduvilla tile?
- Measuring your roof pitch
- Do Onduline roofing sheets sag in hot weather?
- Identifying problems with your roof structure
- Are Onduline roofing sheets better than felt roofing for a shed?
- What is the condition of my roof structure?
- How do you fix the Onduline ridges?
- What structure is my roof?
- How to fix Onduline Verges and Edges
- Measuring purlin or timber batten spacing / distance
- Fixing Eaves
- Where to fix Onduline accessories
- Fixing the Hip Detail
- What tools are needed for installing Onduline sheets?
- How to Fix the Eaves Trays
- What’s the difference between Onduline roofing and metal roofing?
For many sheds, garages and other outdoor buildings, ONDULINE sheets can be installed directly onto the roof structure. Just make sure you follow the installation instructions for your project.
The short answer is no, it is not strictly mandatory for the structure to stay upright, but it is highly recommended as best practice depending on what type of building you are roofing.
Onduline sheets themselves are waterproof, but like all corrugated roofing, they are susceptible to condensation build-up underneath.
You can generally get away without a membrane if you are roofing:
Uninsulated Garden Sheds: Standard, well-ventilated timber sheds usually don't need one.
Carports, Open Gazebos, and Lean-tos: These structures have so much natural airflow that condensation rarely accumulates.
Some Agricultural Buildings: Provided there is significant, continuous ridge and eaves ventilation to sweep moisture away.
Why the Membrane Matters (Even on a Shed)
Even if Onduline keeps the rain out, warm air inside a building hits the colder Onduline sheet at night, creating condensation. Without an underlay membrane, this water can drip onto your tools, bikes, or timbers.
A breathable membrane acts as a two-way shield:
It allows internal water vapor to escape through the roof structure.
It acts as a secondary waterproof barrier against wind-driven rain or snow that might get blown under the overlaps.
Consult the Fixing Guides for full instructions.