The Ultimate Guide to Curved Roofs: Pros, Cons, Cost

What is a Curved Roof?

A curved roof is a fairly new design that concentrates on aesthetic more than durability. Whether you’re interested in getting one for its style or because it’s a requirement for the type of building you’re developing, you probably want to learn more before you jump right in and start the building process. Fortunately, you’re in luck, because this article can help answer any questions you may have about curved roofs, which is a specialty type of design that very few contractors have the expertise to install.

History of Curved Roofs

The round-roof barn, which is one of the earliest examples of curved roofs, was first seen in the 1920s. Its design came from people who were attempting to maximize the space in their lofts for hay storage. Since then, many barn type roofs have been redone with round roofs, and many of them were built during periods of world war. Most of the pre-World War II barns that have round roofs are scattered throughout the United States, and they can mostly be found in the mid-West. Curved roof construction that does not have supporting side walls became very popular after 1945, and ones that were designed more superiorly began to be seen in the 21st century.

Pros and Cons

Like all other types, roofs with a curved design have various advantages and disadvantages. Here are the pros and cons:

Pros

• Visually appealing – If you’ve ever seen a curved roof before, then you know how pleasing it is to the eye. They tend to have a modern visual appeal that not only looks spectacular but also gives an edgy feel to any building. Owners looking to give a “wow” factor to their property will find this type ideal.
• Ability to be customized – Since curved roofs are specifically designed by an architect, they can be customized to match the area where the building is located and the tastes of the owner. Architects will also be able to provide options for different curved roof framing techniques.
• Relatively low requirements for maintenance – Many curved roofs are simple and have characteristics that are similar to a standard shed roof. Because of this, they’re typically wind-resistant and require low maintenance.
• Eco-friendly – Curved roofs are eco-friendly because they have been found to contribute to the reduction of harmful CO2 emissions. In-plane roof lights, which have also been proven to be economical, can easily be installed on the roof.
• Popular with developers – Ease of construction makes this type popular with developers. The reduced height of the curve for these roofs is usually favorable for height restrictions.

Cons

• They need to be designed carefully – You’ll need the expertise of an experienced architect when building a curved roof because the roof needs to be designed for maximum comfort and efficiency.
• The cost depends heavily on design – The cost of the curved roof will depend on many different factors, including but not limited to the area of the roof, the height of the curve, and materials used to cover the roof.

Types of Curved Panels

Panels for roofs come in many different shapes. They include:

1. Barrel-vaulted panels – Otherwise known as convex curves, barrel-vaulted is the most common design with an outward consistent curvature that creates a convex shape. When it is reversed (turned inward), it’s known as a concave curve.
2. S-shaped curve panels – This complex curvature type combines convex and concave curves.
3. Elliptically and hyperbolically curved panels – These freeform panels allow architects unrestricted design options when it comes to creating curved surfaces.

Curving Methods

A panel can be curved through a variety of methods, including:

• Basic curved method – This is a curve that the panel will naturally curve to without being forced or strained, which would possibly create creases or visual deformations. This method is also known as the “lay-down” or “walk-down” method.
• Mechanically curved method – This method is used to create a curve that’s tighter than what a natural curve would permit. Panels start as straight and are curved by a machine through a set of forming and curving rollers. The rollers compress and stretch the panel into a curved shape.
• Crimp curved method – This method is used when there is a continuation of the roof down the building’s facade and a soft visual edge is preferred over a sharp edge.

Material Selection

Almost any type of material can be used for curved tile roofs (including stainless steel, aluminum, copper, galvanized steel, and zinc), but some materials are easier to bend than others. For example: Aluminum, copper, and zinc (especially aluminum) are good choices for tighter panel systems because they allow for a tighter curve. Softer and more ductile materials are typically preferred for curving metal panels, but they’re not required. The most cost-effective approach involves using steel for larger curvature and aluminum for tighter ones.

What are the profiles and materials available for crimp curved systems?

• Profile(s) – LT7
  • Materials available – Steel G550, Steel G300, Aluminum H34
• Profile(s) – V-Rib
  • Materials available – Steel G550, Steel G300
• Profile(s) – Styleline, Hi Five
  • Materials available – Steel G550, Steel G300, Aluminum H34

Recommended Curve Radius

When designing curved applications, the radius of the different panels needs to be kept in mind because if they don’t fit the desired radius well, forcing them to conform may cause buckles or waves in the panel pan or vertical legs.

Minimum Curve Radius

For each profile, this radius is restricted by the appearance of the roof sheet. A minimum curve radius can help ensure the clean appearance of a roof with minimal ripple effect.

Maximum Curve Radius

For each profile, this radius is restricted by the need to have a profile reach its minimum recommended pitch at the gutter line. This ensures large radius “flat” roofs are not used and that water catchment will not overfill the profile valleys because of insufficient run-off.

Installation Details

Now it’s time for the installation. There are certain things to keep in mind when it comes to the installation of a curved roof, regardless of the design and the types of materials you’re using. Here what you should know about the framing and fasteners as well as the sheet termination:

Framing and Fasteners

When it comes to the fitting and final appearance of the roof, it’s essential that the purlin and/or girt framing is located true to line. The final appearance will be better with a tighter tolerance, with a recommended tolerance from the true purlin alignment being ±5mm.

Sheet Termination

Ends of sheets that are underneath head flashings and stop-ended cannot terminate at zero or negative pitch. To make sure this doesn’t happen, it is recommended to base the design on sheet termination at a pitch that’s at least to the minimum pitch of the profile used.

Contact Us For More Information

At Legacy Service, we’re here to help you. If you’re thinking of building a curved gable roof, looking for rounded roof shingles, or wondering how to build a curved roof line, we’ll help you get what you’re looking for. Give us a call at 215-798-9790 to schedule a free consultation for a roof replacement.