Understanding Parallel Chord Roof Truss Framing

Parallel chord roof trusses are a type of roof truss that consists of two parallel chords, or top and bottom plates, connected by webs.

These trusses are often used in residential construction because they are relatively easy to build and require minimal materials.

In a parallel chord roof truss, the top chord is typically the highest point of the truss, while the bottom chord is the lowest point. This configuration allows for a clear span of up to 40 feet.

The webs in a parallel chord roof truss are usually spaced 16 inches on center, which helps to provide additional support and stability to the truss.

There are several types of parallel chord roof trusses, each with its own unique characteristics.

The Howe truss is a type of parallel chord roof truss that consists of two sloping chords and a series of diagonal web members.

Fink trusses are another type of parallel chord roof truss, characterized by a series of triangular shapes that form the web of the truss.

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A common type of parallel chord roof truss is the Warren truss, which is known for its simplicity and ease of construction.

The Pratt truss is a type of parallel chord roof truss that consists of two sloping chords and a series of diagonal web members, similar to the Howe truss.

The Queen post truss is a type of parallel chord roof truss that is similar to the Fink truss, but has a more complex web configuration.

The K truss is a type of parallel chord roof truss that is known for its simplicity and ease of construction, making it a popular choice for many builders.

A parallel chord roof truss is a popular choice for vaulted ceilings, providing a more thermally efficient alternative to conventional cut roofs with steel apex beams.

These trusses eliminate the potential for thermal bridging and allow for a greater depth for insulation, typically 450-600mm+.

Ideal for use where you have gable apex windows, parallel chord trusses offer a unique design opportunity.

They are also a good option when trying to add a second floor to a garage, as they can help maximize space.

To create parallel chord roof trusses, you can use software like Chief Architect Premier X15, Home Designer Pro 2024, or newer versions.

In these programs, you can select Build > Framing > Build Framing from the menu, then access the Roof and Trusses panels to set your preferences.

For example, you can change the Maximum Horizontal Span on the Trusses panel to 30" for both the Top and Bottom Chord.

Alternatively, you can create parallel chord roof trusses manually by selecting Build > Framing > Roof Truss from the menu and drawing a truss perpendicular to the ridge line of the roof and ceiling planes.

To create multiple copies of the truss, use the Multiple Copy edit button and set the Offset Between Copies When Dragging to the desired O.C. truss spacing.

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The trusses located on each end of the structure will be a full-size truss, but you can group select the trusses and open them up to specification to create end trusses instead.

Here's a quick guide to creating parallel chord roof trusses:

You can create parallel chord roof trusses in Chief Architect using two methods: automatic and manual.

Automatic trusses can be generated by selecting Build> Framing> Build Framing from the menu, accessing both the Roof and Trusses panels, and verifying that the settings are set to your liking. This method is available in Chief Architect Premier X15, Home Designer Pro 2024, and newer versions.

To create trusses manually, you can select Build> Framing> Roof Truss from the menu, click and drag to draw a roof truss, and then adjust its settings as needed.

Here's a comparison of the two methods:

Both methods allow you to create parallel chord roof trusses, but the manual method gives you more control over the truss settings and layout.

Scissor trusses can be a cost-effective option for vaulted ceilings, with costs comparable to fink or queen post trusses with flat ceilings.

Some builders have explored the use of parallel chord trusses, which can provide better insulation depth than conventional rafters, but this option can be expensive and take up more space.

In one scenario, a homeowner considered building a second story, but ultimately decided against it and opted for a single story with scissor trusses.

Automating roof truss creation can save you a lot of time and effort. You can automate this process in Chief Architect Premier X15, Home Designer Pro 2024, and newer versions.

To start, select Build > Framing > Build Framing from the menu. In the Build Framing dialog that appears, click on the Framing Defaults button. This will allow you to set up your roof framing settings to your liking.

You can access both the Roof and Trusses panels in the dialog and verify that the settings are set to your liking. For example, you can change the Maximum Horizontal Span on the Trusses panel for both the Top and Bottom Chord to 30", and remove the check from the Ridge box on the Roof panel.

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Once your roof framing settings are set up, click OK, check the appropriate Roofs box in the Build Framing dialog, then click OK. Automatic trusses, along with any other automatic framing components, such as blocking and fascia boards, will be generated.

Here are some key settings to keep in mind when automating roof truss creation:

The trusses located on each end of the structure will be reduced gable end trusses. If you don't want these types of trusses to be built automatically, you can open the two gable walls up to specification, select the Roof panel, and uncheck the "Include Automatic End Truss Above" box.

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Manual roof truss creation can be done manually in software, allowing for precision and control over the design. To start, select Build > Framing > Roof Truss from the menu.

Click and drag to draw a roof truss perpendicular to the ridge line of the roof and ceiling planes. This will create the initial truss. You can then move it so that the exterior edge of the truss is aligned with the exterior edge of the framing layer of the wall.

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To modify the truss, select it and click the Open Object edit tool. This will open the Roof Truss Specification dialog, where you can change the Maximum Horizontal Span for both the Top and Bottom Chords.

For example, you can specify 30" for both the Top and Bottom Chords. Then, click OK to apply the changes. With the truss still selected, you can create multiple copies of it by using the Multiple Copy edit button.

To set the spacing between the trusses, use the Multiple Copy Interval button to open the Multiple Copy dialog. Here, you can verify that Offset Between Copies When Dragging is selected and set the Primary Offset to the desired truss spacing. In this example, the default Primary Offset value of 24" is used.

You can also use the Transform/Replicate edit tool in Home Designer Pro, which allows you to create multiple copies of an object by setting the Number of Copies, checking the Copy box, and setting the X Delta to the desired spacing.

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