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Cross Section Of A House Roof

How a Roofing Structure is Supported

A good roof protects you from the elements, but in order to get one, you need to deal with roofing contractors.

That’s not so bad — except for the fact that half of the time, you won’t understand what we’re saying. Roofing structures have many parts and pieces, each of which has its own name. And sadly, roofing contractors probably won’t take the time to explain everything, so you might be completely confused.

Don’t worry, though — we’re here to help. Read on to find out everything you need to know about roofing structures and their various parts!

What Is a Roofing Structure?

Before you actually put a roof in place, you need some sort of a frame to support it and guide your work. This frame is called a roofing structure. It’s the part of the roof that’s underneath the shingles or tiles, so you can’t see it once the construction is done.

A roofing structure is a series of beams, trusses, and rafters. In a typical residential home in Florida, all of these parts are made of lumber. After all, it is the most convenient material to use — easy to produce, cheap, and strong.

The type of roofing structure your home will have largely depends on its architecture and the roof covering. Simple residential houses usually have medium-pitched roofing structures, while more regal homes use steep-pitched ones. Then, depending on the roofing structure, the roof can be low, medium, or steep-pitched.

The roof covering determines how strong your roofing structure will be. For example, if you’re using asphalt shingles, which are quite lightweight, the roofing structure doesn’t have to be so sturdy. But slate and similar heavy materials need more reinforcement — so your roofing structure has to be stronger too.

Parts of a Roofing Structure

Now that you know what a roofing structure is, let’s tackle the biggest issue — all the parts and pieces that hold it together.


house rafter system roof construction
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Rafters are diagonal beams that meet at the top and provide the main support for the roof deck and its load. Basically, it’s the part that gives your roof its steep shape.

Collar Beam

collar beam connecting two rafters

Collar beams are horizontal, and they connect two rafters that meet at the ridge. Usually, they are placed right under the ridge and don’t allow the rafters to sag. Sometimes, we call these beams collar ties.

Ridge Board

At the very peak of the roof, you’ll find the ridge board. This horizontal beam holds all the rafters together — they basically meet at the ridge board. Made of metal or timber, it is the part that brings the whole structure together and makes it cohesive.

Top Plate

The top plate is another supporting beam — but this one connects rafters to the wall studs. It supports the roofing structure and transfers all the load onto the load-bearing walls and the foundation.

You might also come across the term cantilevered top plate, which has the same function but is supported only on one end.

Ceiling Joist

wood ceiling joists holding up roof

Ceiling joists are parallel to collar beams, but they are under them — around the base of the construction. Their purpose is to support the rafters from below, much like the ridge board and collar beam do from above.

Fascia Board

The fascia board runs along the lower edge of the roof and disguises the ends of the rafters. It also supports the bottom row of tiles once they’re put in place.


Underpurlins are horizontal beams that you might see somewhere around the middle of the rafters. They make the rafters more stable and allow them to cover longer spans. Usually, you can see underpurlins in long buildings — such as the traditional U.S barn.


Struts are vertical beams that support and transfer the load from underpurlins onto the strutting beams. They add stability to the whole structure and maintain its rigidity.

Strutting Beam

The strutting beam is horizontal and parallel to the ridge board. Its main purpose is to transfer the load onto the load-bearing walls when there are no available wall studs.

Elements That Go Over the Roofing Structure

A roofing structure is the foundation of the roof — but alone, it won’t do you much good. Once you have the roofing structure in place, it’s time to add other elements in order to make a fully functioning roof.

Sheathing or Decking

Decking goes directly onto the roofing structure and closes it, providing a base for shingles. Usually, it looks like a flat sheet of bare material — most commonly plywood. More lightweight roofs sometimes have decking made of OSB (oriented strand board).


Roofs typically have steep slopes, so you’d expect water to just slide off them, right? Unfortunately, there are joints and chimneys, as well as areas where water might gather, and it’s important to protect them.

That’s exactly what flashing is for — it’s supposed to keep those areas dry and protected. Thus, it’s usually made of metal that deflects water, making it slide off instead of pooling on the roof.


Just like you, your roof needs to breathe. If too much hot air gathers in the roof area, it can significantly reduce its lifespan. For that reason, we usually install ventilation around the roof ridge and edges. It’s under the covering, so you don’t need to worry that it will ruin your roof’s appearance.

Roof Covering

Finally, on top of everything, we have the roof covering. As we said before, asphalt shingles are the most common option, but you can also use wood, slate, clay, concrete, and even metal coverings.

The covering needs to be durable and able to protect your house from rain and wind. Still, it doesn’t hurt if it looks good too. After all, it’s the only visible part of the roof!

To Conclude

Roofs may seem pretty simple on the outside — but there’s a lot to them underneath the surface. Now that you know that, we’re sure you’ll take roof maintenance quite seriously. And you’ll actually understand what your roofing contractor is talking about!

About the Author

Prime Roofing specializes in residential roof replacements in the Jacksonville area. Do you need to have your roof installed? Contact us today and schedule a free estimate! Give us a call between Monday-Friday 8AM to 5PM at (904) 530-1446.

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