What is the structure of a steel roof?

A steel roof is an incredibly durable and long-lasting roofing option made from steel panels or sheets. But what exactly goes into constructing a steel roof system? In this blog, I'll walk through the components and structure behind these heavy-duty roofs to give you an inside look into what makes them last for decades.

The Decking

The foundation of a steel roof starts with the decking or substrate that the steel panels or sheets are attached to. The decking provides the base layer that transitions from your roof's framework to the exterior steel roofing material.

Many homes use plywood decking that is at least 5/8" thick as the surface to fasten steel panels or sheets to. The plywood provides a smooth, sturdy surface for attaching and supporting the steel roofing. Other decking options can include oriented strand board (OSB) panels, wood planks, or even a steel deck.

The Key Benefits:

Creates an attachment surface for steel panels/sheets to be securely fastened

Smooths out any uneven spots on the roof framework

Provides a protective separation between framework and steel roofing

Underlayment Before the steel roofing goes on, a roofing underlayment is installed above the decking material. Synthetic underlayments, like felt paper, help to further protect the roof decking and interior of the home.

The underlayment creates a waterproof barrier beneath the steel roof. So if any water/moisture manages to get through cracks or joints in the steel panels above, the underlayment blocks it from seeping into the decking and interior ceilings below.

The Key Benefits:

Creates waterproofing beneath steel panels

Adds another moisture barrier for extra leak protection

Steel Panels or Sheets Now we get to the visible exterior layer - the steel roofing material itself! Steel roofing comes in a variety of forms, but metal panels or sheets are two of the most common.

Metal Roof Panels: These are modular steel panels that interlock together to create the roof surface. They can have exposed fasteners or a standing seam design. The interlocked panels create a water-tight barrier.

Metal Roof Sheets: These are solid steel sheets that get overlapped and attached to the roof deck. Corrugated sheets are a popular choice as the ridges add strength and structural stability compared to flat sheets.

Both panel and sheet designs take advantage of steel's strength and weather-resistance. With protective finishes like zinc or aluminum applied, the steel itself will resist rust/corrosion for 30+ years.

The Key Benefits:

Extremely durable against wind, rain, snow loads

Resists dents and damage from hail or falling debris

Won't rot, warp, or burn like other roofing materials

Reflective nature helps reduce cooling costs

Structural Components Underneath those top steel roofing layers are some important structural parts:

Roof Battens: Thin strips of material (often wood) that run from the eave to the ridge in between roof rafters. They provide an attachment surface for steel sheets/panels to be screwed into.

Purlins: Horizontal structural beams that span perpendicular along the rafters and roof battens. They provide intermediate support by transferring weight loads across the roof's surface.

Rafters: These angled framing components give the roof its overall slope and structural shape by extending from the roofline walls up to the peak point. The rafters transfer the roof's weight loads down the exterior walls.

Sheathing: Sheets of exterior grade material (often plywood or OSB) that are fitted together to create the outer shell of the roof assembly. The sheathing gets attached on top of the roof rafters to complete the substrate that roofing materials are affixed to.

The primary purpose of these structural parts is to fully support and distribute the weight of the steel roofing along with any additional live/snow loads. The result is a sturdy framework capable of handling heavy steel panels for 30 years or longer.

Insulation One optional component for extra energy efficiency is insulation. This can either be installed along the roof's rafters/sheathing or underneath the roof decking layer.

The insulation creates a protective thermal barrier to help regulate interior temperatures. This means cool air stays inside during hot summer months and warm air stays trapped inside when it's cold out.

The result is a more comfortable living space year-round plus reduced cooling/heating costs. Insulation paired with a reflective steel roof amplifies those energy saving benefits further.

Finishing Touches The final details complete the full structure:

Ridge Vents: Located where roof planes meet to allow hot air escape along the ridge. This improves air circulation and cooling.

Roof Penetrations: Any vents, pipes, ducts, or skylights that penetrate the waterproof barriers are properly flashed/sealed to prevent moisture entry points.

Gutter System: Installed around roof perimeter to safely collect rain runoff and channel water away from the structure into downspouts. Necessary for water management.

And there you have it! A complete breakdown of what goes into constructing a durable steel roofing system. From decking to insulation to finishing details, each layer and component works together to create a reliably weather-tight covering that will protect your home for 30 years or more. The combination of strength, corrosion resistance, fire protection and energy savings make steel roofs a go-to roofing solution.

If you want to get more information about steel roof structure, you can contact us at sales6@leadersteelstructure.com