Curved and arched roofs are a popular choice across agricultural, industrial and commercial buildings, offering both structural strength and visual appeal. But can corrugated steel sheets be used on curved and arched roofs?
Widely known for their durability, lightweight construction and cost-effectiveness, corrugated steel roofing sheets can be suitable for some curved or arched structures. However, their performance depends on several key factors, including the roof radius, steel profile and installation method.
In this article,we will explore why corrugated steel sheets are suitable for some curved or arched roofs, how they are curved, installation considerations and their overall performance.
What Are Corrugated Roofing Sheets?
Corrugated roofing sheets are steel sheets formed with a distinct repeating wave-like profile.This corrugation increases the sheet’s strength while keeping it lightweight and helps rainwater drain away rather than pooling.
Corrugated sheets are manufactured in a range of coatings, including galvanised, polyester and plastisol, with each option offering a different balance of protection and value.
Can Corrugated Steel Sheets Be Used On Curved Or Arched Roofs?
Yes, in many cases, provided the curve is gentle enough. Corrugated roofing sheets are suited to many curved and arched roofing applications where the curve is gradual rather than tight.
When installed correctly, the sheet follows the arc of the roof without compromising the building’s structural integrity. However, corrugated sheets are not innately flexible. Their ability to follow the curve of a roof depends on the roof’s radius, the sheet thickness and the profile depth. There are two main ways of curving:
- Natural (Spring) Curving: On gentle curves with a large radius, straight sheets can be flexed into shape on site as they are fixed to curved purlins.
- Pre-Curving: Sheets are curved in a factory to the exact radius before delivery.
Which Curved And Arched Roofs Are Suitable For Corrugated Sheets?
As established, corrugated roofing sheets are not suitable for all curved or arched roofing structures. However, there are some which are suitable:
1. Arched Or Barrel-Vault Roofs
Found on agricultural and industrial buildings, arched and barrel-vault roofs are well suited to corrugated steel roofing sheets.
The sheets are laid along the natural curve of the roof, flexing gradually without compromising strength or weather resistance.
2. Shallow Curves
Shallow or gentle curves and arches are suitable for corrugated roofing sheets.
Their large radius places minimal stress on the sheets and fixings, making installation more straightforward and sheets can often be curved naturally on site.
How To Curve Corrugated Steel Sheets
Curving corrugated steel is a common requirement when creating curved roofs or arched structures.The method you choose depends on the sheet thickness, the desired radius and the scale of your project.
Spring Curving
For gentle arches with a large radius, corrugated sheets can be spring curved (also known as sprung curved) on site.
The sheets are flexed over purlins that are already set to the curve of the roof and fixed in place, with the corrugations running along the curve.
Pre-Curved Sheets
Some manufacturers offer corrugated steel sheets that are pre-curved to a specific radius.
This ensures consistent curvature and reduces the risk of errors during installation.
Manual Bending
Bending sheets by hand, for example over a curved pipe or former, should only be considered for small-scale projects with very gentle curves and large radii.
Forcing a sheet by hand can kink the profile or crack the coating, which may affect the coating guarantee. Always follow the manufacturer’s guidance.
Minimum Radius Considerations
Each corrugated steel sheet has a minimum recommended curve radius, both for natural curving on site and for factory curving.
If you attempt to force the sheets beyond this limit, you can deform the sheet, damage the coating and reduce its performance.
Factors which impact the minimum radius include:
- Sheet thickness
- Corrugation depth
- Material type
- Coating type
- Direction of the curve
- Purlin spacing
- Sheet length
You should always consult the manufacturer’s guidance to ensure the chosen profile is suitable for the intended roof radius.
Installation Considerations For Curved Roofs
Installing corrugated roofing sheets correctly is critical for ensuring structural integrity, weather resistance and a long lifespan.
You must consider:
- Installing corrugated sheets along the curve rather than across it
- Using appropriate fixings to accommodate potential movement
- Avoiding excessive force during the installation process
- Allowing for thermal expansion or contraction
- Using continuous sheets over the crown of the arch where possible, or sealing end laps if not, as the roof is almost flat at the top and water runs off more slowly
The curved framing, such as the purlins or rafters, should be designed by a structural engineer to suit the roof radius and loads.
Safety first: Curved roofs are harder and riskier to work on than pitched roofs. Installation should be carried out safely, in line with the Work at Height Regulations 2005 and HSE guidance, ideally by a competent roofing contractor.
Advantages Of Using Corrugated Steel Sheets On Curved Roofs
Corrugated metal roofing sheets offer several advantages when used on curved and arched roofs, making them a popular choice across agricultural, industrial and commercial buildings.
These are:
Lightweight And Structurally Strong
The profile of the corrugated sheet increases its strength without adding any unnecessary weight.
Natural Flexibility For Gentle Curves
Corrugated steel sheets are more adaptable than flat metal sheets, allowing them to follow gentle curves and arches.
Cost-Effective Roofing Solution
Compared to bespoke profiles, corrugated roofing sheets are a more cost-effective option.
Efficient Water Run-Off
The corrugated profile promotes effective drainage, reducing the risk of standing water and helping maintain weather-tight performance, provided the crown of the arch is detailed correctly.
Wide Range Of Finishes And Specifications
Corrugated steel sheets are available in various thicknesses, coatings and colours.
Advanced specifications, including anti-condensation roofing sheets, are also available to meet both functional and aesthetic requirements. Check with your supplier whether your chosen specification can be curved to the radius you need.
When Corrugated Sheets May Not Be The Best Option
While corrugated roofing sheets are versatile and cost-effective, they are not suitable for every curved or arched roof application.
Situations where alternative roofing solutions may be more appropriate include:
- Very tight or complex curves
- Where a smoother, more architectural finish is wanted
- Where specific acoustic or thermal performance is needed, such as with insulated roof sheets
By understanding these limitations, you can ensure the right roofing solution is selected for both performance and appearance.
Still deciding on a profile? Read our guide to box profile vs corrugated wall cladding.
Corrugated Roofing Sheets At Cardinal Steels
Corrugated roofing sheets are a durable, cost-effective and versatile solution for many curved and arched roof applications, when the curve is gentle and proper installation practices are followed.
At Cardinal Steels, we offer expert guidance and nationwide delivery of high-quality corrugated steel roofing sheets.
Get in touch today for advice and guidance from start to finish.
