Know Your Own House: Components of a Roof

When you have installed your base, put down your flooring construction and erected your walls, it’s time to construct your roof — one of the most significant architectural elements. In reality, in the colonial house with its gable roof to a Prairie-style house with its hip roof, from a modern house with its low-sloping roof to an elegant mansard in an urban townhouse, we can’t envision a house design that does not have its associated roof configuration. Aligning the roof shape and configuration with the general aesthetic you’re after is vital to getting the look you desire.

A roof also has an impact on the inside. In other words, if all the interior rooms have a level ceiling of the exact same height, you can save money and time and have the roofing constructed with manufactured trusses. If you’re trying to find some ceiling height variety along with a vaulted ceiling in some rooms, you will probably go with a stick-built roof which allows for this kind of flexibility. Or you may combine both of these approaches to save time and money where possible whilst getting those special spaces you desire.

Here are the different pieces of a simple roof construction, the way they come together and how they impact the inside spaces.

Bud Dietrich

A easy, stick-built triangular roof construction has three chief components.

First, there’s a ridge board, that’s a flat wood element at the summit of the roof, establishing the apex of the roof’s triangle.

Next would be the rafters, which are fastened to the ridge board and slope downward to the exterior walls. The rafters do the heavy lifting to get a roof construction. While resisting the downward force of gravity, the sloping rafters also provide the means by which the house sheds water, maintaining the interiors rancid and dry.

Last would be the ceiling joists, which also behave as ties. While the rafters resist the downward force of gravity, then the ceiling joists will resist any external thrust. Just think of it like that: The rafters, having stood up to gravity, wish to take a break and lie. But if they had been allowed to, they would push the exterior walls external — not a good thing. The ceiling joists will not let this happen; they just keep pulling the walls back in.

Bud Dietrich

An important design consideration is where to find the ceiling joists, or rafter ties. These do not have to be set on peak of the exterior wall; they may be set higher up, letting for a taller ceiling.

What’s significant is that the rafter ties be placed in the lower third of the general roof construction height. This makes sense, because most of the outward thrusting actions these ties are intended to resist is located lower in the roofing construction, closer to where the rafters meet the exterior walls.

Putting the ceiling joists higher like this really is, with the addition of some framing in the space ends, and the process used to create a tray ceiling.

Bud Dietrich

Let’s say you want a very tall vaulted ceiling for a large great room. If that is the case, you’re going to want to eliminate the rafter ties completely and replace the thin and light ridge board using a thicker and more powerful ridge beam.

The rafters will get firmly fastened to the ridge beam so that the whole assembly will resist the outward push of the rafters. And because these ridge beams are often quite massive, they turned into a distinctive architectural element in their own right.

Bud Dietrich, AIA

Another roofing element, though not a common person, is the purlin. That is a board which spans rafters, or trusses, providing a means to secure the roof sheathing and subsequent roofing materials.

Purlins were traditionally utilized when the rafters were placed farther apart to save on substances in pragmatic buildings such as barns. But purlins have become popular in residential construction due to their exceptional architectural look. In reality, using purlins will create the illusion that the actual ceiling floats above the rafters, something which may be architecturally distinctive.

Bud Dietrich, AIA

Last but not least are manufactured trusses made of 2-by-4 (occasionally 2-by-6) lumber and metal connecting plates. Trusses such as these are used quite often on big tract developments due to the efficacy of the repetitive layout.

But these trusses are also utilized in custom construction also, as they may be a fantastic way to save money and time. Even with a intricate roof silhouette, trusses could be engineered and constructed on a made-to-order foundation. And due to the efficient utilization of substance and less waste created when they’re built in a mill, manufactured trusses could be a more sustainable way to construct.

One thing about a house built with these types of trusses: A roof constructed with manufactured trusses is more challenging to modify than a similar stick-built roof. If your house has ceilings all the exact same height along with a truss-built roof, then you’ll find it more challenging to open up rooms and find that tall ceiling you want for this brand new great room. Make sure you get support from an architect or architect until you alter the roofing construction. Learn about different kinds of trusses in house layout

More in Know Your Own House:
What Makes Up Your Home’s Foundation
What Makes Up a Floor Structure
Components of Efficient Walls

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